engine lubrication

© 2012 Delmar, Cengage Learning

Engine Lubrication

Chapter 12


Objectives• Describe engine lubrication under different

service conditions• Select the correct engine oil to use• Describe the operation of different types of oil

filters


Introduction• All moving parts

are separated by a thin oil layer– Oil pump supplies

oil to the engine

– Little wear should occur if oil is maintained properly


Engine Oil• More than basic crude

– Contains a complicated additive package• First additives were developed in the 1930s

• Does more than lubricate– Cools, cleans, and prevents rust

– Fills hydraulic valve lifters or cam followers

– Helps seal piston rings against cylinders


Engine Oil (cont'd.)• Oil level

– Correct level is designed to keep the oil pickup screen below the level of the oil

– When checking oil level:• Vehicle should be on a level surface• Engine should be warm but off for five minutes• Push dipstick all the way down• If level is unclear: look at back of dipstick or re-dip• If level is low: check if the vehicle is due for

service


Engine Oil (cont'd.)• Oil viscosity

– Oil thickness or body

• Multiple viscosity oils– Most new engine oils

are multiple viscosity

• Viscosity index – Ability to resist

change in viscosity under increased heat


Engine Oil (cont'd.)• Oil pressure

– Develops when there is a resistance to flow

– As engine wears, clearance between crankshaft and bearings increases

• Oil pump cannot fill extra clearance• Oil pressure is low when engine idles

– SAE 20W-50 provides higher oil pressure in older, idling engines

• Flows more slowly to bearings of new engine when first started on a cold morning


Engine Oil Licensing and Certification

• SAE decides when new oil specifications are needed– American Society for Testing and Materials

• Sets performance specifications

– American Petroleum Institute • Administers the licensing and certification

• Starburst symbol– API licenses engine oil marketers to display its

starburst certification mark


Engine Oil Licensing and Certification (cont'd.)

• Oil service ratings– Set by API– SA through SN

• SA: mineral oil with no additives and is not recommended for automotive use

• S: used for engines with a spark

– Diesel engine oils: rated CA through CJ


Engine Oil Licensing and Certification (cont'd.)

• European ACEA oils– ACEA standards developed by European auto

manufacturers

• Manufacturer-specific oil standards– Becoming more common

• Energy-efficient oils– Oil is energy conserving if it passes certain tests

• Energy conservation ratings began in 1994

• HTHS viscosity rating– Measures viscosity under difficult conditions


Oil Additives• Additives make up as much as one-third of the

volume of the oil• Additives found in engine oil

– Pour-point depressants

– Corrosion and rust inhibitors

– Antifoam additives

– Friction modifiers

– Oxidation inhibitors

– Antiwear additives


Oil Additives (cont'd.)• Boundary lubrication

– Film becomes too thin or breaks down under load

• Detergents and dispersants – Keep small particles suspended

• As oil decomposes at high temperatures it reacts with oxygen to form a gummy mixture

• Detergents make deposits oil soluble

• Sludge – Mixture of moisture, oil, and contaminants

• Clogs oil screen and oil lines if it accumulates


Oil Additives (cont'd.)• Nondetergent oil

– Oil without additives is called

• Oil oxidizes at temperatures higher than 250°F– Becomes thicker and forms varnish deposits

– Oxidation rate doubles every 20°F above 140°F

– Antioxidants combat the effects of heat on the oil

– Detergents make varnish oil soluble


Synthetic Oils• Molecules are nearly the same size

– Reduces friction

• Contain no wax or impurities – Suited to lower temperatures

• Can also withstand higher temperatures

• Advantages– Lower oil consumption

– Can be changed less frequently

• Disadvantage– Price


Changing Engine Oil• Benefits of changing the oil

– Oil additives are depleted over time

– Cleans smaller contaminants from the oil

– Unburned contaminants are removed with the oil

– Sludge is removed

• Oil change intervals– Vehicles driven primarily on the highway can

change oil every 7,500 miles

– Newer engines with VTT require regular oil changes with high-quality, low-viscosity oil


Changing Engine oil (cont'd.)• Changing brands of oil

– Avoid mixing brands between oil changes

– Best done when the oil is being changed

– Use any brand of high-grade oil when there is no choice of brand available

• Changing oil– Best to change oil when it is still hot

• Mileage service record: usually a sticker

• Oil monitor system reset– Included in many late-model vehicles


Oil Filter• Prevents harmful abrasive particles in the oil

from damaging internal parts– Today's cars use the full-flow oil filter

• Must have a by-pass valve

– Horizontal mounted filters • Have an anti-drainback valve

– By-pass oil filters• Supplemental add-on filters used on heavy trucks

• Variations in filters– Identified by a number printed on the metal shell


Changing the Oil Filter• Considerations

– Sheet metal shell on filter is very thin

– Rubber O-ring seals filter against engine block• Make sure there is not an old seal stuck to the

engine block• Lubricate the O-ring with oil prior to installation

– Most filters have instructions printed on the outside

– Overtightening will make future removal difficult

engine lubrication

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