<8S^ J f ft j j f f^ The Engineering Society
`For Advancing Mobility
`Land Sea Air and Space
`
`400 COMMONWEALTH DRIVE WARRENDALE, PA 15096
`
`861516
`
`Oils in Taxicab Service
`Donald J. Smolenski and Richard H. Kabel
`Genera] Motors Research Labs.
`
`Reprinted from SP-676—
`Worldwide Lubricant Trends
`
`International Fuels and Lubricants Meeting
`and Exposition
`Philadelphia, Pennsylvania
`October 6-9,1986
`
`Page 1 of 14
`
`ORONITE EXHIBIT 1013
`
`

`

`The popsn included in this rohimt
`are abstracted and indexed in [hi1
`5A£ Global Mohilin- Database
`
`SAE GLOBAL MODiUTY
`
`No part of this publication may be reproduced in any form,
`in an electronic retrieval system or otherwise, without the
`prior written permission of the publisher.
`
`ISSN 0148-7191
`Copyright 1986 Society of Automotive Engineers, Inc.
`
`This paper is subject to revision. Statements and opinions
`advanced in papers or discussion are the author's and are
`his responsibility, not SAE's; however, the paper has been
`edited by SAE for uniform styling and format. Discussion
`will be printed with the paper if it is published in SAE
`Transactions. For permission to publish this paper in full or
`in part, contact the SAE Publication Division.
`
`Persons wishing to submit papers to be considered for
`presentation or publication through SAE should send the
`manuscript or a 300 word abstract of a proposed manu(cid:173)
`script to: Secretary, Engineering Activity Board, SAE.
`
`Printed in U.S.A.
`
`Page 2 of 14
`
`

`

`861516
`
`[valuation of Camshaft and Lifter Wear5 Deposits,
`and Oil Thickening with Low-Phosphorus Engine
`Oils in Taxscab Service
`Donald J. Smolensk! and Richard H. Kabel
`General Motors Research Labs.
`
`ABSTRACT
`
`A 160 000-km taxi test was run to determine
`the effects of low-phosphorus engine oils on
`engine durability. Camshaft and lifter wear,
`deposits, and oil-thickening were evaluated in
`thirty vehicles with oil-change intervals pur(cid:173)
`posely extended to increase test severity.
`Three SAE 5W-30, SF, low-phosphorus (=0.06 mass
`percent) oils and two SAE 10W-30, SF/CC, normal-
`phosphorus (=0.11 mass percent) oils were
`evaluated.
`
`Overall engine durability and performance was
`satisfactory with two of the three low-
`phosphorus, and one of the normal-phosphorus
`oils, and unsatisfactory (because of high wear)
`with the other oils.
`
`These results demonstrate that low-phosphorus
`oils can be provided if further phosphorus
`reduction is necessary to protect emission con(cid:173)
`trol systems, and that current normal-phosphorus
`oils must be properly formulated to protect
`engines.
`
`IT IS WELL DOCUMENTED THAT PHOSPHORUS
`originating from engine oil generally poisons
`emission control devices (1-4).* Therefore,
`reducing engine oil phosphorus concentrations
`should improve the performance of emission
`control devices. To reduce the amount of
`phosphorus reaching these devices, GM divisions
`are maximizing oil economy (consistent with good
`engine durability), while we are evaluating
`means of safely reducing the amount of phospho(cid:173)
`rus in the engine oil. Others at GMR and
`AC Spark Plug are developing more phosphorus-
`resistant catalysts and oxygen sensors. Oil
`economy in many new GM models is 8 000 km/L or
`better. Further improvements in oil economy
`will be difficult to achieve, and may not be
`
`* Numbers in parentheses designate references at
`end of paper.
`
`advisable, since periodic oil additions replen(cid:173)
`ish depleted additives. Thus, further reduc(cid:173)
`tions in phosphorus poisoning of current-design
`and existing emission control devices will
`likely result from reductions in engine oil
`phosphorus content. However, future emission
`control devices may be more tolerant of phospho(cid:173)
`rus, as well as more efficient and durable.
`The major phosphorus-containing compounds
`in engine oil are zinc dialkyldithiophosphates
`(ZDP's), which are thought to provide wear
`protection by decomposing and reacting with
`metal surfaces to form a protective coating
`(5-10). They also function as antioxidants,
`primarily by decomposing peroxides (11,12).
`Thus, injudicious reduction of engine oil
`phosphorous concentrations could result in
`increased camshaft and lifter wear and oil
`oxidation.
`The taxicab test discussed in this paper
`was conducted to compare the wear protection
`performance of three specially-formulated, low-
`phosphorus-content engine oils with that of two
`normal-phosphorus-content oils. We also anal(cid:173)
`yzed used-oil-drain samples by various methods
`described in an earlier paper (13) to determine
`ZDP levels and depletion rates.
`
`EXPERIMENTAL TEST PROGRAM
`
`ENGINE OILS — Physical and chemical
`inspection data for the test oils are shown in
`Table 1. The two normal-phosphorus-content
`reference oils, HI-10 and HI-12, were SF/CC-
`quality (14), SAE 10W-30 (15) commercially-
`available oils. The three low-phosphorus-
`content oils, LO-05, L0-06, L0-07, were
`SF~quality, SAE 5W-30 experimental oils. Oil
`L0-07 was formulated with a partial-synthetic
`base stock.
`TEST FLEET — Yellow Cab Company of
`San Diego, California, permitted us to use
`thirty 1981 Chevrolet Malibu taxicabs. All were
`equipped with Buick 3-8-L, V-6 engines with pro(cid:173)
`duction D-500 lifters and California emission
`
`63
`
`Page 3 of 14
`
`

`

`TABLE 1 — Physical and Chemical Inspection Data - New Oils
`
`Oil Code:
`
`HI-12
`
`HI-10
`
`SAE Viscosity Grade
`API Service Classification
`Viscosity,
`cP
`cSt at 40°C
`cSt at 100°C
`cP at 150°C andlO6 s"1
`
`10W-30
`SF/CC
`
`10W-30
`SF/CC
`
`3100 (-20°C)
`68.5
`11.5
`3.oo
`
`'C}
`2050 (-18=
`61.5
`9.4
`2.95
`
`Total Acid Number
`Total Base Number
`
`Sulfated Ash, Mass Percent
`Metals, Mass Percent
`
`P
`Ca
`Zn
`8a
`Mg
`Na
`M
`
`1.5
`6.2
`
`1.0
`
`0,12
`0.13
`0.13
`<0.01
`<0.01
`0.13
`—
`--
`
`2.9
`7.5
`
`1,0
`
`0.10
`0.23
`0.11
`<0.01
`<0.01
`<0,01
`—
`—
`
`LO-07
`
`5W-30
`SF
`
`--
`57.8
`11.2
`2.96
`
`2.2
`7-7
`
`0.84
`
`0.066
`0.05
`0.07
`<0.01
`0.08
`<0.01
`—
`—
`
`LO-06
`
`5W-30
`SF
`
`LO-05
`
`5W-30
`SF
`
`2C)
`3120 (-25'
`3170 (-25°C>
`59.0
`64.1
`10.0
`10.8
`3.16
`2.83
`
`3.8
`6.1
`
`0.53
`
`0.054
`<0.01
`0.054
`<0.01
`0.06
`<0.01
`0.12
`0.02
`
`6.8
`7.1
`
`0.80
`
`0.046
`v.0.01
`0.057
`<0.01
`0.12
`<0.01
`0.06
`0.01
`
`Base Stock Type:
`
`ineral
`
`Mineral
`
`)2% Synthetic
`887. Mineral
`
`Mineral
`
`Mineral
`
`control systems. Six taxicabs were operated on
`each of the oils.
`MILEAGE ACCUMULATION — All taxicabs were
`operated in low-speed, stop-and-go service in
`the metropolitan San Diego area from April 1981
`to January 1984. The tests were scheduled for
`160 000 kin, but, due to factors unrelated to the
`oil test, accumulated distances ranged from
`154 296 tan to 171 644 km.
`The vehicles were fueled with unleaded
`gasoline. To increase test severity, oil and
`filters were changed e^ery 8 000 ± 800 km by cab
`fleet personnel. Based on previously reported
`results {13), this extension from t- ; recom(cid:173)
`mended 4 800 km oil-change interval generally
`provides a substantial increase in se"erity.
`Used oil filters were sent to AC Spars-. Plug
`Division of General Motors where they were flow-
`checked for plugging.
`ENGINE INSPECTIONS AT END OF TEST — At the
`end of the test, cab company personnel removed
`and returned to GMR an engine from one vehicle
`run on each oil. In addition, the camshafts and
`valve lifters from all the remaining vehicles
`were removed and sent to GMR for measurement and
`inspection.
`Sludge, varnish, and intake valve deposits
`were rated using Coordinating Research Council
`(CRC) merit rating scales, where 10 denotes a
`clean part and 0 denotes a part completely
`covered with heavy deposits (16). The oil ring
`spacers and rails were weighed, cleaned ultra-
`sonically in Cities Service Solvent S-26, and
`reweighed to determine the weight of deposits.
`
`Visual inspections were made of connecting rod
`and main journal bearings. Qualitative observa(cid:173)
`tions of scuffing were also made of all upper
`valve train parts. Since the engines were not
`premeasured, wear was computed by comparing
`measurements of camshaft lobe lift and lifter
`crown height to nominal, new-part or production
`tolerances.
`Lifter foot distress was evaluated by
`inspecting the lifters for scuffing, or adhesive
`wear; spalling, or fatigue wear; and pitting, or
`chemical attack. Of these three phenomena,
`scuffing is believed to be most serious; it
`generally causes excessive wear of the mating
`camshaft lobe. Combined camshaft lobe and
`lifter wear >500 urn was considered excessive.
`Once this much wear occurs, subsequent wear is
`usually extremely rapid (17).
`
`RESULTS AND DISCUSSION
`
`Camshaft and lifter wear observations and
`data, and oil consumption data for all
`30 engines are given in Appendix A, Table A-1.
`Deposit data for the five engines which were ....s
`completely disassembled are also included. In
`the following sections, these results are summa(cid:173)
`rized and discussed in detail.
`STATISTICAL ANALYSES — Oil consumption
`rates and combined camshaft and lifter wear and
`distress data from all 30 engines were computer
`analyzed using Duncan's and Tukey's tests (18).
`These tests determine whether or not the mean
`value of a variable (such as average camshaft
`
`64
`
`Page 4 of 14
`
`

`

`and lifter wear) varies from one class (such as
`oil type) to the next. The former determines if
`the extreme values of a parameter differ signif(cid:173)
`icantly; the latter separates the means into
`groups which are statistically different at a
`given percent significance level (5 percent).
`Statistical analyses of deposit and other wear
`data were not possible since only one engine on
`each oil was completely disassembled and rated
`(i.e., there was only one observation, instead
`of six, for each oil). Significance of the
`differences noted among oils is, in these cases,
`based on engineering judgment.
`CAMSHAFT AMD LIFTER WEAR — Mean and
`maximum camshaft and lifter wear values with
`each oil are summarized in Figure 1 and Table 2.
`There were no statistically significant differ(cid:173)
`ences (at the 5 percent significance level)
`among oils with respect to either mean or maxi(cid:173)
`mum camshaft plus lifter wear results, Direc-
`tionally, however, wear was least with two of
`the low-phosphorus oils, LO-06 and LO-07, inter(cid:173)
`mediate with HI-10, and greatest with LO-05 and
`HI-12. However, the high mean wear values
`observed with oil HI-12 are due primarily to a
`wear failure in one engine (see data for cab T^M
`in Appendix A). If the data from this engine
`are excluded, mean average and mean maximum com(cid:173)
`bined camshaft and lifter wear for this oil are
`211 and 371 ym, respectively. As this illus(cid:173)
`trates, data from a single engine can unduly
`influence overall mean wear results for an
`oil. For this reason, it is often useful to
`apply another criterion, the incidence of exces(cid:173)
`sive wear, in judging an oil's performance.
`INCIDENCE OF EXCESSIVE CAMSHAFT WEAR —
`Moderate, although not excessive, levels of
`camshaft and lifter wear would probably not have
`a perceivable (to the vehicle driver) effect on
`engine operation. However, excessive camshaft
`wear, which we also define as wear >500 pm,
`generally greatly degrades engine performance
`and adversely affects exhaust emissions, neces(cid:173)
`sitating replacement of the camshaft and
`lifters. Thus, the incidence of excessive
`camshaft wear is suggested as another criterion
`for ranking oils, and should be more representa(cid:173)
`tive of real world (customer-perceived) oil
`performance. (For example, if wear were gener(cid:173)
`ally higher with oil A than with oil B, but 1
`percent of a fleet's vehicles which used oil B
`experienced camshaft failures, whereas only 0.5
`percent of the vehicles which used oil A expe(cid:173)
`rienced failures, oil A would likely be
`perceived as the better oil.)
`
`In Table 3, the oils are ranked with
`respect to the number of engines in which exces(cid:173)
`sive camshaft wear was observed. Excessive cam(cid:173)
`shaft wear was not observed with either oil
`LO-06 or LO-07, which indicated that these two
`low-phosphorus oils provide acceptable wear pro(cid:173)
`tection in this engine and type of service.
`Excessive camshaft wear was observed on several
`lobes in one out of six of the engines operating
`on oil HI-12. This result was judged to be
`acceptable, based on consideration of the
`extended oil-change interval (8 000 km vs.
`
`1600n
`
`1200-
`
`Bars represent range
`of values observed.
`Asterisks represent
`mean values.
`
`Maximum
`Camshaft
`and Lifter
`Wear.Mm
`
`800-
`
`400'
`
`• D
`
`LO-05 06
`
`07
`Oil
`Fig. 1 Combined camshaft and lifter wear.
`
`r~
`—i
`10 12
`
`TABLE 2 — Camshaft and Lifter Wear
`
`Engine
`Oil Code
`
`SAE
`Viscosity
`
`Mean Combined Camshaft
`
`and Lifter Wear, urn
`Avg.
`Max.
`
`LO-05
`LO-06
`LO-07
`
`HI-10
`HI-12
`HI-12*
`
`5W-30
`5W-30
`5W-30
`
`10W-30
`10W-30
`10W-30
`
`* w/o Cab 744
`
`306
`169
`151
`
`221
`317
`211
`
`622
`375
`335
`
`577
`715
`371
`
`TABLE 3 — Excessive Camshaft Wear
`
`Engine
`Oil Code
`
`SAE
`Viscosity
`
`LO-05
`LO-06
`LO-07
`
`HI-
`HI-
`
`10
`12
`
`5W-30
`5W-30
`5W-30
`
`10W-30
`10W-30
`
`Number of
`Engines With
`Excessive
`Camshaft
`Wear*
`
`Rank
`
`3
`1
`1
`
`3
`2
`
`* One or more camshaft lobes worn >500 ym.
`
`4 800 km recommended for this type of service)
`and the test length {160 000 km) involved. The
`incidence of excessive camshaft wear was
`unacceptable with oils LO-05 and HI-10. The
`phosphorus (i.e., ZDP) content of oil L0-05 was
`the lowest of all the oils, and apparently the
`additive package could not provide adequate wear
`protection at this phosphorus level. The ini(cid:173)
`tial batch of oil HI-10 was reported by the oil
`
`65
`
`Page 5 of 14
`
`

`

`supplier to be misformulated {slightly under(cid:173)
`rated with additive package}. It is not know if
`the excessive camshaft and lifter wear results
`observed with this oil may be partially due to
`initial mileage accumulation on the misformu(cid:173)
`lated oil. (It should be noted that the engine-
`dynamometer tests were run on the properly-
`formulated version of this oil. Also, several
`samples from high wear engines were analyzed for
`glycol, but none was found.} These results
`point out that proper blending, as well as
`sufficient ZDP, are needed to ensure satis(cid:173)
`factory protection against engine wear.
`TAXICAB TEST WEAR VS. SEQUENCE AND TOYOTA
`18R TEST WEAR — Table 4 contains wear results
`from Sequence H ID and V~D tests (19}, and
`Toyota 18R (20,21) tests on the taxicab test
`oils. Average taxi test camshaft and lifter
`wear (average of six cabs on each oil) corre(cid:173)
`lates surprisingly well (r = 0.91)* with
`Sequence H ID test average wear (see Figure 2 ),
`considering the large difference in the oper(cid:173)
`ating conditions of the two tests. The
`regression line does not pass through the
`origin, however, possibly due to the relatively
`high break-in wear rate in the Sequence H ID
`test. However, the correlation between maximum
`wear results from the taxicab and Sequence H ID
`tests is not as good (r = 0.10), which is not
`unexpected, because of the larger variability
`inherently associated with excessive wear
`rates. Correlation between Sequence V-D and
`taxicab test wear results is also not as good
`(r2 = 0.11). The Sequence H ID test, in this
`case, is probably more predictive of average
`taxicab test wear results than the Sequence V-D
`test because the valve train configuration is
`similar between the taxicab engine and
`Sequence H ID engine (camshaft in block and
`rotating lifter). The Sequence V-D engine, on
`the other hand, has a considerably different
`
`valve train configuration (overhead camshaft and
`solid followers).
`No clear correlation is evident between
`Toyota 18R cold test data and taxicab test wear
`results (average taxicab wear vs. Toyota wear,
`r2 = 0.24). With oil HE-10, for instance, no
`camshaft nose wear occurred in the Toyota 18R
`test cold cycle, yet high wear occurred in the
`taxi test. Wear with oil LO-05 was high in the
`taxicab test and low in the Toyota 18R test cold
`cycle, but high in the hot cycle (49 um vs.
`50 ym maximum limit). Perhaps the hot cycle of
`the Toyota 18R test is more predictive of field
`service than the cold cycle. Unfortunately,
`hot-cycle data for the other four oils are not
`available.
`BEARING WEAR -- Early bearing failures
`occurred in two cabs operating on the misformu(cid:173)
`lated oil HI-10. Although it is doubtful that
`the oil significantly contributed to the bearing
`problem, data from these two engines were not
`used/included in the paper. Instead, new engines
`were installed in these vehicles and the test
`was restarted. No excessive bearing wear or
`distress was observed subsequently with any of
`the oils.
`
`350
`
`300
`
`250-
`
`Avg. Taxi Test
`Wear, um
`
`60
`50
`Avg. Sequence HID Wear, \im
`
`70
`
`„2
`
`-
`
`index of determination.
`
`Fig. 2 Comparison of Sequence HID and
`t e st camshaft and l i f t er wear.
`
`taxi
`
`TABLE 4 — Taxicab, Sequence H I D, Sequence V-D, and Toyota 18R Test Results
`
`Engine
`Oil Code
`
`SAE
`Viscosity
`
`Taxicab
`Oil
`Ranking
`
`HID
`Sequence
`C + L
`Wear, urn
`Avg.
`Max.
`
`Sequence V-D
`We ar, vim
`C + L
`Max.
`Avg.
`
`Toyota 18R**
`Cam
`Rocker Pad
`Pitting,
`Scuffing,
`Demerits
`Demerits
`
`Cam Nose
`Wear, urn
`
`20(49)
`40
`—
`
`0
`8
`
`LO-05
`L0-06
`LO-07
`
`HI-10
`HI-12
`
`5W-30
`5W-30
`5W-30
`
`10W-30
`10W-30
`
`Passing Limits
`
`3
`1
`1
`
`3
`2
`
`63
`48
`41*
`
`46
`66
`
`178
`157
`58"
`
`86
`119
`
`10s
`15
`18*
`
`23
`11
`
`15*
`18
`18*
`
`30
`15
`
`1.4(0)
`13.9
`1K9
`
`0
`65.3***
`
`0(0)
`0
`--
`
`0
`0
`
`100.
`max
`
`200,
`max
`
`25
`max
`
`63
`max
`
`20
`max
`
`20.
`max
`
`50
`max
`
`* Test run on homologue of taxi test oil,
`** Cold cycle results, except values in parentheses are from hot-cycle tests.
`*** 100 h tests results, normal test length 200 h.
`
`66
`
`Page 6 of 14
`
`

`

`ENGINE DEPOSITS — Upon test completion,
`one engine run on each oil was completely
`disassembled, inspected, and rated for deposits.
`Sludge, average engine varnish, piston skirt
`varnish, and intake valve deposits were rated
`using CRC (16) rating methods. In addition, oil
`ring deposit weights and the percentage of oil
`screen plugging were determined. These data are
`contained in Appendix A, Table A-1.
`The sludge ratings for all of the oils were
`similar and all were 2.9-3 (the Sequence V-D SF
`performance requirement is 9.4) indicating rela(cid:173)
`tively sludge-free engines. These results were
`similar to those from an earlier test using this
`same engine model and taxicab fleet (13).
`Average piston skirt varnish (P.S.V.)
`ratings ranged from 6.7 for oil LO-07, to 5.0
`for oil L0-05. Since both different additive
`packages and base stocks were involved in the
`test oils, it is not possible to relate the
`observed performance differences to either
`additive chemistry or base stock characteris(cid:173)
`tics. All average piston skirt varnish ratings,
`except for that for oil LO-07, were below the
`Sequence V-D SF requirement of 6.7. However, no
`operational problems as a result of these depo(cid:173)
`sits were reported. These ratings were also
`generally lower than those observed in the
`previous taxicab test (13) (overall average
`P.S.V. rating of 6.0 for this test compared to
`6.8 for the previous test). The reason for this
`increased severity is unknown.
`Average engine varnish ratings (consisting
`of the average rating for the rocker covers,
`front cover, intake manifold center gasket,
`etc.) ranged from 8.4 for oil L0-06, to 5.0 for
`oil L0-05. The ratings for all oils except for
`oil LO-05 were greater than the Sequence V-D
`SF performance requirement of 6.6, and were
`judged acceptable.
`Intake valve back deposit ratings ranged
`from 4.7 for oil LO-05, to 2.8 for oil LO-07.
`All deposits were excessive, possibly due to
`both engine design {moderate oil consumption,
`possibly via intake valve seals), type of
`service (low-speed, extensive Idling), and
`extended oil-change interval. These deposit
`levels are unacceptable, but it is not known if
`they are a direct result of an oil performance
`deficiency.
`Total oil control ring deposits ranged from
`1.92 g for oil HI-12, to 3-75 g for oil HI-10.
`Since no operational problems occurred as a
`result of these deposits, deposit levels were
`considered acceptable.
`Oil screen plugging was considered to be
`minimal (<.10 percent) with all five oils.
`LIFTER STICKING — The average number of
`cold-stuck lifters per engine for each oil is
`shown in Table 5. Sticking was excessive with
`oil LO-07, moderate oils LO-05, HI-10, and
`HI-12, and minimal with oil L0-06. Chemical
`analyses were performed on deposits from the
`surface of a lifter plunger from the engine
`operated on oil LO-07 to determine the cause of
`the high sticking rate. The deposits were
`analyzed by infrared spectroscopy and found to
`
`be primarily oxidized hydrocarbons {possibly
`oxidized engine oil, decomposed fuel, and/or
`combustion by-products). Improved resistance to
`formation of these types of deposits should
`reduce lifter sticking. This would be a
`desirable improvement in the performance of oil
`LO-07.
`OIL CONSUMPTION -- The average consumption
`rate for each oil is shown in Figure 3. Oil
`consumption rates were generally acceptable and
`typical for this engine and type of service with
`all oils, although they were somewhat high with
`oil HI-12. There was no statistically signif(cid:173)
`icant difference (at the 5 percent significance
`level) in oil consumption between the SAE 5W-30
`and SAE 10W-30 oils.
`
`0.8
`
`Bars represent range
`of values observed.
`Asterisks represent
`mean values.
`
`0.6
`
`Oil
`Consumption,
`L/1000 km 0.4
`
`0.2
`
`mi/qt
`
`-1000
`
`•1500
`
`-3000
`
`0.0
`
`LO-05 06
`
`—r~
`07
`Oil
`Fig. 3 Oil consumption r a t e.
`
`— j_
`10 12
`
`OIL FILTER PLUGGING — From 31 to 44 o il
`f i l t e rs
`for each o il were flow-checked
`for
`(A
`plugging at AC Spark Plug Division (22).
`f i l t er
`is considered plugged if
`the pressure
`drop across it
`is greater
`than 69 kPa at a flow
`r a te of 0.38 L/sec.) The percent of
`f i l t e rs
`plugged for each o il
`is shown in Table 5.
`F i l t er plugging with a ll of the o i ls was accept(cid:173)
`able in l i g ht of the extended oil-change
`i n t e r(cid:173)
`val used in t h is t e s t.
`Plugging with the
`three
`SAE 5W-30 o i ls was somewhat higher than that for
`the two SAE 10W-30 o i l s. The reason for t h is
`is
`unknown, although it
`is speculated
`that it may
`be related
`to the fact
`that the SAE 10W-30 o i ls
`met the API CC service c l a s s i f i c a t i o n, whereas
`the SAE 5W-30 o i ls did not. Perhaps, extra
`dispersancy was present in the CC o i ls and
`reduced the o i l - f i l t er plugging.
`
`it
`
`TABLE 5 — L i f t er S t i c k i ng and O il F i l t er Plugging
`
`Engine
`Oil
`Code
`
`SAE
`Viscosity
`
`Average Mo,
`of Cold-Stuck
`Lifters/Engine
`
`Lifter
`Sticking
`Tendency
`
`Percent of
`Oil Filters
`Plumed*
`
`LO-05
`L0-06
`LO-07
`
`HI-10
`HI-12
`
`5W-30
`5W-30
`5W-30
`
`10W-3O
`10W-30
`
`5.0
`2.2
`9-7
`
`6.5
`4.7
`
`Moderate
`Low
`High
`
`Moderate
`Moderate
`
`14
`20
`26
`
`0
`10
`
`Pressure drop across f i l t er equal to or exceeding 69 kPa.
`
`67
`
`Page 7 of 14
`
`

`

`USED OIL ANALYSES — Used oil samples were
`retained at every oil change for all taxicabs,
`but only those from every third oil-change
`interval (i.e., 24 000, 48 000, 72 000, 96 000,
`120 000, 144 000 km, and E.O.T.) were analysed.
`The following properties were determined:
`
`• Viscosity at 40 and 100°C {D-445)s
`• Total Acid Number (D-664)*
`• Total Base Number (D-2896)*
`• Pentane Insolubles (D-893)*
`• Mass Percent Metals (D-811)*
`• Infrared Spectrum
`• Oxidation Induction Time (References 24
`and 25)
`
`Because of the large number of samples
`involved (approximately 210), data from analyses
`on individual samples are not included in this
`report. Rather, pertinent data are summarized
`in the next several sections. Bar graphs will
`be used to show the range in values observed for
`the given parameters for each of the oils at the
`various intervals.
`VISCOSITY — The range (for six taxicabs on
`each oil} of viscosity increase for each oil is
`shown in Figures 4a and 4b. Oil thickening
`(viscosity increase) was low for oils HI-12 and
`L0-07, and for all but one drain interval for
`oil HI-10. With oil HI-10, the % 000-km oil
`sample from one cab showed a 256 percent viscos(cid:173)
`ity increase, whereas the other five samples
`averaged 18 percent. The reason for the abnor(cid:173)
`mal viscosity increase with one sample is
`unknown. Thickening was moderate, but still not
`abnormal, with oils L0-05 and L0-06. Although
`viscosity increase overall was higher with the
`low-phosphorus oils than with the normal-
`phosphorus oils, oil LO-07 provided evidence
`that it is possible to obtain good resistance to
`thickening with low-phosphorus oils in this type
`of service. (It would be useful to know whether
`or not these oils also provide good oxidation
`resistance in actual high-speed, high-
`temperature service.) No systematic variation
`in oil thickening was observed with test length
`(i.e., engine age), except that, in general, the
`variability observed in the results (i.e., the
`height of the bars) increased with test length.
`OXIDATION INDUCTION TIME — Differential
`Scanning Calorimetry (DSC) was used to determine
`the oxidation induction times of used oil
`samples. An isothermal scan (at 167°C) was made
`under a static oxygen atmosphere of 3450 kPa
`(see References 24 and 25). The length of time
`required for oxidation to begin (as evidenced by
`exothermal behavior) is termed the oxidation
`induction time. Generally, the longer the
`induction time, the more oxidatively stable an
`oil is. It is the authors' opinion based on
`experience that induction times of less than
`15 minutes coincide relatively well with the end
`of useful oil life. A time of three minutes or
`
`* ASTM test method in Reference 23.
`
`250'
`
`200'
`
`150
`
`100
`
`50
`
`Percent
`Increase
`in
`Viscosity
`at 40°C
`
`OIL
`woLO-05
`i^aLO-06
`*»« LO-07
`
`Bars represent
`range of values
`observed
`
`wmm
`
`24 48 72 96 120 144 160 ,
`Test Length at Drain, km x 10v
`
`increase with
`Fig. 4a Change in viscosity
`mileage — SAE 5W-30 o i l s.
`
`250 n
`
`OIL
`
`SSiSHI-12
`
`Percent
`Increase
`in
`Viscosity
`at 40°C
`
`200-
`
`150
`
`100
`
`5 0-
`
`% Bars represent
`6
`range of values
`^ observed
`
`I
`
`%h%%%\%
`
`24 48 72 96 120 144 160 ,
`Test Length at Drain, km x 10'
`
`Fig. 4b Change in viscosity increase with
`mileage — SAE 10W-30 oils.
`
`less indicates that an oil has been used beyond
`its useful life and is generally depleted of
`antioxidant.
`Figures 5a and 5b show the range of used
`oil induction times for each oil at the various
`oil-drains. The only apparent (significant)
`variation in induction time with test length
`occurred with oil LO-06. Extremely high values
`were first observed, followed by a sharp fall
`off and then a leveling out. The oxidation
`induction times for oil L0-06 were generally
`higher than those for the other oils. Somewhat
`surprisingly, the observed viscosity increase
`was generally greater with this oil. Perhaps
`this apparent anomaly can be explained in terms
`of the fact that ZDP, the major antioxidant in
`most engine oils, is also the major antiwear
`additive. In fact, camshaft and lifter wear for
`
`68
`
`Page 8 of 14
`
`

`

`Oxidation
`induction
`Time, min
`(by DSC)
`
`120
`
`1 0 0-
`
`8 0-
`
`4 0-
`
`20
`
`0
`
`Bars represent
`range of values
`observed
`
`OIL
`^ LO-05
`H9B LO-06
`i ^ L O - 07
`
`Induction times shown are averages
`of seven used oil samples {24, 48, 72,
`96, 120, 144 000 km and E.O.T.) for
`each of six vehicles on each oil.
`2500
`
`A
`
`2000-
`
`•
`1500-
`
`Maximurn
`Camshaft
`and Lifter
`Wear, um 1 0 0o
`
`-©
`
`O
`
`{
`500
`
`A
`
`o
`
`Oil
`o LO-05
`• LO-06
`m LO-07
`O Hi-10
`A HI-12
`
`o a
`3
`
`a
`
`a
`
`O
`
`o
`
`1—
`1
`—!
`j
`,
`1
`1
`24 48 72 96 120 144 160 .
`Test Length at Drain, km x 10'
`
`60
`40
`20
`Avg, DSC induction Time, min.
`
`80
`
`Fig. 5a
`
`Change in oxidative s t a b i l i ty with
`mileage — SAE 5W-30 o i l s.
`
`Fig. 6 Camshaft and lifter wear as a function
`of used oil DSC induction time.
`
`120-i
`
`1 0 0-
`
`OIL
`'///Ml-10
`ssssHI-12
`
`Oxidation
`Induction
`Time, min
`(by DSC)
`
`80
`
`40
`
`20 H
`
`!
`v %
`
`Bars represent
`range of values
`observed
`
`,
`9
`
`g li
`
`0
`
`24 48 72 96 120 144 160 ,
`Test Length at Drain, km x 10*
`
`Fig. 5b Change in oxidative stability with
`mileage — SAE 10W-30 oils.
`
`oil L0-06 was lower than that for any of the
`other oils. These DSC results may be more
`indicative of ZDP activity, and hence antiwear
`activity, and not as representative of oxidative
`stability, or resistance to thickening. DSC
`conditions of high pressure and temperature do
`not accurately simulate overall engine sump
`conditions, but may reflect those at the
`camshaft/lifter interface.
`Figure 6 shows the relationship between the
`average used oil oxidation induction time vs.
`maximum camshaft and lifter wear (Ref. 13
`comparison was based on new oil). Although
`scatter is evident, the highest wear is gen(cid:173)
`erally observed with oils having low induction
`times. However, low induction times do not
`necessarily always result in high wear rates
`(Oil KI-12). Ho excessive wear occurred where
`
`the average induction time of the used oil was
`greater than 30 minutes. Thus, it appears that
`excessive wear does not occur as long as the
`used oil shows moderate antioxidant activity.
`The absence of such activity does not neces(cid:173)
`sarily result in excessive wear, however,
`(Ashless supplemental wear inhibitors used in
`low-phosphorus engine oils may have little or no
`antioxidant activity.)
`PENTANE INSOLUBLES — The range of pentane
`insolubles content for each oil at the various
`drain intervals is shown in Figures 7a and 7b.
`Pentane insolubles were generally highest with
`oil LO-07, followed by oil HI-10. Mo apparent
`relationship exists between pentane insolubles
`and the amount of sludge and varnish deposits
`observed. However, lifter cold-sticking was
`more prevalent with the two oils having high
`pentane insolubles. Perhaps the insolubles
`contribute to lifter sticking; however, no
`support for this was found in the literature.
`Insolubles were initially high with oil LO-05,
`but were lower in samples from later drains.
`The reverse trend was observed for oil L0-06.
`Again, the reason for the variation in insol(cid:173)
`ubles observed with test length is unknown, but
`it is speculated that the type and amount of
`dispersant used is probably involved. Insol(cid:173)
`ubles were low for all drain samples with oil
`HI-12, indicating good dispersancy with this
`oil. Pentane insolubles were somewhat lower
`overall with the normal-phosphorus-content
`oils. It is speculated that this may be more a
`function of the increased dispersancy required
`to meet the CC performance classification than
`of the increased ZDP concentration in these
`oils.
`
`TOTAL BASE NUMBER — For each oil, the
`average change in total base number (TBN) of the
`used oil from that of the new oil is shown in
`Figures 8a and 8b. (Data for increases in TAN
`
`63
`
`Page 9 of 14
`
`

`

`Average
`Pentane
`Insolubles,
`Percent
`
`10-,
`
`8
`
`6-
`
`4-
`
`2-
`
`0
`
`,—
`,
`—,
`J . —,
`24
`48
`72 96 120 144 160
`Test Length at Drain, km x 10'
`
`Fig. 7a Change in pentane insolubles content
`with mileage — SAE 5W-30 o i l s.
`
`Bars represent
`range of values
`observed
`
`Bars represent
`range of values
`observed
`
`8 -i
`
`OIL
`'///. LO-05
`I S L O - 06
`SS3LO-07
`
`New Oil
`TBN -
`Used Oil
`TBN
`
`1
`1
`1
`1
`T
`T
`T
`24 48 72 96 120144 160
`Test Length at Drain, km x 10
`8a Change in reserve a l k a l i n i ty with
`mileage — SAE 5W-30 o i l s.
`
`Fig.
`
`Average
`Pentane
`Insolubles,
`Percent
`
`10-i
`
`8-
`
`4
`
`2
`
`OIL
`^ H I - 10
`ass HI-12
`
`Bars represent
`range of values
`observed
`
`OIL
`
`KSSHI-12
`
`Bars represent
`range of values
`observed
`
`l l!
`1
`' * I
`. 4 L 1 &. 4.
`
`'4
`
`'/s Y/
`
`6
`
`24 48 72 96 120 144 160 ,
`Test Length at Drain, km x 10'
`
`New Oil
`TBN -
`Used Oil
`TBN
`
`•III
`h rir1
`
`ill
`i
`
`I I i.
`i %
`-~r~
`—r-
`48 72 96 120 144 160
`24
`Test Length at Drain, km x 10'
`
`Fig. 7b Change in pentane insolubles content
`with mileage — SAE 10W-30 oils.
`
`Fig. 8b Change in reserve alkalinity with
`mileage — SAE 10W-30 oils."
`
`showed similar trends, but are not presented.)
`Loss of TBN was greatest for oils 10-06 (which
`also exhibited the greatest average viscosity
`increase) and LO-07. Successively lower TBN
`losses occurred with oils HI-10, HI-12, and
`LO-05. No systematic variation in TBN with test
`length was observed.
`
`SUMMARY
`
`Thirty 1981 Chevrolet Malibu sedans,
`equipped with Buick 3.8-L, V-6 engines and
`California emission controls, we