Engine Lubrication

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