
LUBRICATION0-14
SAE5W-30oilsmaybeusedduringperiodswhen
temperaturesof32°andbelowaretobeexpected.
TypesofOils
Inservice,crankcaseoilsmayformsludgeandvarnish
andundersomeconditions,corrosiveacidsunlesspro-
tectedagainstoxidation.
Tominimizetheformationoftheseharmfulproducts
andtoassuretheuseofoilbestsuitedforpresentday
operatingconditions,automobilemanufacturershavede-
velopeda seriesofsequencetestsdesignedtoevaluate
theabilityofanyoiltoproperlylubricateautomobile
engines.
Itisrecommendedthatonlythoseoilswhichare
certifiedbytheirsuppliersasmeetingorexceedingthe
maximumseverityrequirementsofthesesequencetests
(orGMStandard4745-M)beusedinChevroletengines.
Certifiedsequencetestedoilswillbedescribedassuch
ontheircontainers.
MaintainingOilLevel
Theoilgaugerodismarked"Full"and"AddOil."
Thesenotationshavebroadarrowspointingtothelevel
lines.
Theoillevelshouldbemaintainedbetweenthe
twolines,neithergoingabovethe"Full"linenorunder
the"AddOil"line.DONOTOVERFILL.Afteroperating
vehicleallowa fewminutesforoiltoreturntocrankcase
beforecheckingoillevel.
Checktheoillevelfrequentlyandaddoilwhen
necessary.
OilandFilterChangeIntervals
NOTE:
Underprolongeddustydrivingcondi-
tions,
itisrecommendedthattheseoperations
beperformedmoreoften.
OIL
Toinsurecontinuationofbestperformance,lowmain-
tenancecostandlongenginelife,itisnecessaryto
changethecrankcaseoilwheneveritbecomescontami-
natedwithharmfulforeignmaterials.Undernormal
drivingconditionsdrainingthecrankcaseandrefilling
withfreshoilevery60daysorevery6000mileswhich-
everoccursfirst,isrecommended.
Itisalwaysadvisabletodrainthecrankcaseonlyafter
theenginehasbecomethoroughlywarmeduporreached
normaloperatingtemperature.Thebenefitofdrainingis,
toa largeextent,lostifthecrankcaseisdrainedwhen
theengineiscold,assomeofthesuspendedforeign
materialwillclingtothesidesoftheoilpanandwillnot
drainoutreadilywiththecold,slowermovingoil.
OILFILTER
Changeengineoilfilterevery6000milesorevery6
months,whicheveroccursfirst.
NOTE:
ForVehiclesinheavydutyoperation
involvingcontinuousstart-stoporprolongedidl-
ing,engineoilshouldbechangedafter2500-
3000milesofoperation.Thefiltershouldbe
changedafter5000-6000milesofoperation.
CrankcaseDilution
Probablythemostseriousphaseofengineoildeterio-
rationisthatofcrankcasedilutionwhichisthethinning
oftheoilbyfuelvaporleakingbypistonsandringsand
mixingwiththeoilandbycondensationofwateronthe
cylinderwallsandcrankcase.
Leakageoffuel,orfuelvapors,intotheoilpanoccurs
mostlyduringthe"warmingup"periodwhenthefuelis
notthoroughlyvaporizedandburned.Watervaporenters
thecrankcasethroughnormalengineventilationand
throughexhaustgasblow-by.Whentheengineisnot
completelywarmedup,thesevaporscondense,combine
withthecondensedfuelandexhaustgasesandformacid
compoundsinthecrankcase.
Aslongasthegasesandinternalwallsofthecrank-
casearehotenoughtokeepwatervaporfromcon-
densing,noharmwillresult.However,whentheengine
isruninlowtemperaturesmoisturewillcollectand
unitewiththegasesformedbycombustionresultingin
anacidformation.Theacidthusformedislikelyto
causeseriousetchingorpittingwhichwillmanifestitself
inexcessivelyrapidwearonpistonpins,camshaft
bearingsandothermovingpartsoftheengine,oftentimes
causingtheownertoblamethecarmanufacturerorthe
lubricatingoilwheninrealitythetroublemaybetraced
backtothecharacteroffuelused,ora conditionofthe
enginesuchasexcessiveblowbyorimpropercarburetor
adjustment.
AutomaticControlDevicestoMinimize
CrankcaseDilution
Allenginesareequippedwithautomaticdeviceswhich
aidgreatlyinminimizingthedangerofcrankcase
dUution.
Thethermostat,mountedinthecylinderheadwater
outlet,restrictstheflowofwatertotheradiatoruntila
predeterminedtemperatureisreached,thusminimizing
thelengthoftimerequiredtoreachefficientoperating
temperature,reducingthetimethatenginetemperatures
areconducivetovaporcondensation.
Awaterby-passisincludedinthecoolingsystem,
utilizinga holeinthefrontof,thecylinderblock.This
allowsa limitedcirculationofcoolant,bypassingthe
thermostatuntilthermostatopeningtemperaturesare
reached.Thissystemprovidesa uniformcoolanttem-
peraturethroughouttheengine,eliminatinglocalized
hot-spots,improvingexhaustvalvelife,providesfast
warmrupoflubricatingoilandfasttemperaturerisein
thecoolantwhichprovidesfastheateroperationincold
weather.
Athermostaticheatcontrolontheexhaustmanifold
duringthewarmingupperiod,automaticallydirectsthe
hotexhaustgasesagainstthecenteroftheintakemani-
fold,greatlyaidsinpropervaporizationofthefuel.
Anautomaticchokereducesthedangerofrawor
unvaporizedfuelenteringthecombustionchamberand
leakingintotheoilreservoir.
An.
efficientcrankcaseventilatingsystemdrivesoff
fuelvaporsandaidsintheevaporationoftherawfuel
andwaterwhichmayfinditswayintotheoilpan.
CRANKCASEBREATHERCAP
Cleanandre-oilateveryoilchange..
CHEVROLETCHASSISSERVICEMANUAL