476
T X D rSTRI.4 L AlYD E,$-GTNEERING CHEMISTRY
Vol. 17. No. 5
Better Crank-Case Draining Service' By C. M. Larson2 SINCLAIR
REFINING CO., NEWY O R K , N. ' 1
This paper outlines the actual facts of dilution of HE motorist of today list by motor manufacturers, crank-case oil without attempting to delve too deeply has heard that his car for it stands to reason that into the causes for crank-case dilution or remedial needs draining. Some a well-refined motor oil with measures to correct dilution. dealers tell him his engine ample body and medium Data were gathered from dynamometer laboratory should be drained every 700 high flash and fire would be test work of scientific accuracy and also from actual miles, whereas his instrucbetter than a contaminated road performance of automobiles. Curves are detion booklet says another one having a viscosity veloped to display the relationship of dilution effect on figure. On the other hand, slightly heavier than floor oil engine performance. Other curves show the effect of the oil company's service staand with a flash as low as different end point fuels, summer and winter weather tion attendant, who tells the kerosene. changes, varying grades or viscosities of motor oils, motorist that the crank case Inasmuch as the piston seal and piston clearances, on the rate at which the pershould be drained after every has a direct bearing on how centage of dilution increases in the crank case of an 400 miles run in winter and the diluent reaches the crank automobile engine. after 800 miles in summer case, naturally the viscosity, Two simple devices are described by the use of which weather, is frowned upon as which is the characteristic the motorist can determine when his oil has become trying to sell oil, not service. classifying the grade of motor unfit for further use and may be considered dangerous. It is quite true that with the oil, materially affects the perThese devices constitute a pocket laboratory, and make data on hand no figures of accentage of diluent that leaks it possible for the motorist to determine the proper tual miles run as a guide to into the crank case of an times for changing crank-case oil based on the condidraining a certain make of car a u t o m o t i v e e n g i n e . As tion of the oil, and not on arbitrary or average mileage. are reliable, and constitute shown in Figure 2,3 a light only a rule-of-thumb method motor oil will have to be which mav be harmful to the drained a t more frequent motor in some cases and wasteful of oil in others. intervals than either the medium or the heavy grade, a i the The effect of dilution on frictional horsepower (that de- percentage of dilution is much greater per 100 miles. It is rived from dynamometer calculations) is shown by Figure 1true that it is possible to get too heavy an oil so that for the a slight decrease in frictional horsepower at, no load as the oil first few miles excessive dilution will occur, as the oil cannot is diluted. Yet on the other hand, from the maximum reach the walls of the cylinder to form a seal between the brake horsepower curve it is readily seen that there is a de- piston and cylinder walls until it is diluted to the proper cided power loss with increased dilution unless the initial viscosity. It follows that the motor that has been worn will oil is entirely too viscous. If there were no ill effect due to have greater piston clearances, and therefore the effectiveness
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. iloudb Figure 1-Effect
Rud. of Dilution on Frictional Horsepower
Figure 3-Data Taken from Dynamometer Runs on Oakland Motor, Using Five Increments of Undersize Pistons. Thus Duplicating the Stagesof Wear Occurring throughout the Life of a n Automotive Engine
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Figure 5-Composite Curves Plotted from Data Compiled from Runs Made by Sixteen Cars of Various Makes
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Figure 2-Composite Curves Plotted from Results of Dynamometer Test on Nine Grades of Motor Oil Ranging from 185 to 1800 Seconds Sayboit a t 100" F and Road Test Made with Five Standard Makes of Cars Using the Light Medium Heavy, and E& Heavy Motor b i l s of a Well-Known Brand
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Figure 4-Corn osite Curve8 Com iled from Data O b t a g e d from Sixteen ears, Each Making Separate Runs on A . B , C, and D Gasoline
dilution, lubrication engineers would have an easy time getting various grades of motor oils placed on the approved 1
Presented under the title "Crank-Case Dilution" before the Division
of Petroleum Chemistry at the 68th Meeting of the American Chemical SO
ciety, Ithaca, N. Y., September 8 to 13,1924. 2 Supervising engineer
Figure 6-Composite Curves from Data Pertaining t o Nine Different Grades of Oils, Varying in Viscosities and Base of Crude
of piston seal will be more difficult to attain. This is clearly demonstrated in Figure 3. about A , B, ' 1 and we have heard a great grades of gasoline, and have been told that crank-case dilution J . SOC.Automotive Eng , 14,152 (1924), Tables 2 to 6.
progreshively wit11 tlcrrrasing volatilit,y nnd the ic'reirse is: more marked for tlie Iimrier fiicl. This inwease in d i h h J I l with increased end points of the file1 is shown in Figtire 4.
Tl~roiqlrthe tests run on the A , R, C , and D fuels it \ w s :rho dcvclolx:d th8t. during winter operations a more deeided increase iu percentage of dilution was noted than in summer. Tlir c i i r r e for winter weather in I'igure 5 shows a pronounced ,.ontamiirnt,iorr of the crank-case oil due to dilution. Tests lias-c a l s ~ rcvenleii that one or two applications of the vhokcr i n st,arting during cold weather will cause
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m m dilution thau several hundred inilw, of riiiiniiig. Rcalizing that a more compreliensive rervicr should be offered the motor public through the oil service stations, research w r k was startcd to make the "crank-case serviiv" a practical, scientific one. As the foregoing charts show that tlie dilution of the mmk-case oil for a certain make of car is dejmidciit upon the viscosity of the new motor oil, the piston clearance, end point of fuel, tirid running temperature of the motor, as well as other factors not shown graphically, it was necessary to look elsewhere than to :ictual miles run. From Figure 6 it is readily sccn that as the crank-case oil is diluted 6he I3aumi. gravity changes witti t.he viscosity of tlre nil. After rc.peatcd checking of used samples :and then charting the data of gravity change with per cent dilution, an instrument called R "Dilut-o-meter" (Figure 7) was developed. This is simply a hydrometer, and like all such iristruments depends for its readings on t,lie denfiity or specific gravity of tlie liquid being tested. In this ease, howeser, the scale dops not read in terms of BaumE gravity or s p e d k gravity, but in terms which indicate tire condition of the nil-whether good, fair, p o r , or rIangerous-obvia.ting the necessity fri u t q m t a t i o n of resiilts atid thus niakiirg it brbter adapted for general use. Tlie prineiple according to which t.lie instrument operates is that as an oil is rliliit,ad bv fuel it beenines liahter in arxrit,s.
mure n iitg oils \z-lreii new, some oils when new being as light as others idt,cr t l ~ yare diluted beyond the point of satisSart,ory Idxientioil. This variation is taken care of by putting the iiiiliintii~gscale, not directly on the stem of the instrumcnb, but on the sliding sleeve which may he moved up or rlown. 'I'he instrument may be set by putting it in the IICW oil arid ninving the scale to the zero point, or it may be set from hles Siirnished by the makers showing the proper scale setmgs for tlie well-known oils. Sinre lubrication satisfaction depends on the viscosit,y or body of the oil and this body is decreased by dilution as shown i n Figure fi, it was also possible to develop a pocket viseometcr, or Visgage (Figure 8), for crank-case draining deberminstions. The principle of the Visgage is that tlie travel of spheres through two oils is dependent upon their relative viscosities. Tlierefore, if m-e have two parallel inclined tubes of the same size containing the same oil a t the eame t.emperature, too small i;pheres will reach tlie bottom of t,he incline a t the same moment. However, if one oil is twi1.e as viscous as the other, the spirere in the Ireuvier oil will he wdg half [,he way down the
indine \vIiwr tlic sphcrc i n the lighter oil h i i s rcnehrd the hottnm. Thus, if the viscosity of the oil in one tube is known, it is mssihle to evolve n sc:~Ic ..~. m:itli~mntienlly by which 'the viscosity of the unknoivii oil can he read dirertly. Inasmuch as the t,imperatiiri: of the nil in both t,uhes ismild be the stunr a t the time of test,, no tcmpemtiw correction \wuld be required. The accuracy of this instnrinelit. has been shown to run higher t1i:m 95 to 08 per cent i n Saybolt secouds after the operator has become a little experiencod, and at all times tlre error is negligible for practical work. It isso coristructeci that to make a test it is only necessary to insert the nozzle in the used oil and fill like a syringe. The determinatiou is made and t.he viscosity a t 100' I
