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motor oil lubricates engine parts

Motor Oils & Lubricants

by Larry Carley copyright 2019

Without various oils and lubricants, no vehicle will go very far. The engine needs motor oil to lubricate and cool the bearings, pistons, rings, cylinders and other moving parts.

The motor oil you use should meet the viscosity and service ratings recommended in your vehicle owner's manual. Most engines today are factory-filled with 5W-20 because 5W-20 improves cold starting, fuel economy and allows the oil to reach critical upper valvetrain components in overhead cam engines more quickly than heavier viscosity oils. Some European cars specify 0W-20. Most vehicle manufacturers also approve 5W-30 and 10W-30 for year-round driving. But heavier grades such as 20W-40, 20W-50, straight 30W, etc. are formulated for higher temperatures and loads, and are too thick for cold weather driving. Using a heavier viscosity oil in a late mode vehicle with variable valve timing may adversely affect the operation of the cam phasers and set a trouble code. So follow the viscosity recommendations in your owners manual.

What Type of Motor Oil Should You Use?

There are three basic types of motor oil: conventional, synthetic and synthetic blends.

Conventional mineral oils are refined from crude stock and treated with additives such as detergents, viscosity improvers, anti-wear agents and corrosion, oxidation and foam inhibitors to improve their performance. Many conventional motors oils today such as 5W-20 actually contain high quality base oils similar to those used in synthetic products.

Synthetics are man-made and highly refined to provide the best possible lubrication under the widest range of operating conditions, including extreme temperatures both hot and cold. Synthetic oils can withstand conditions that cause ordinary oils to oxidize and break down. They provide superior high-temperature protection, easier cold-weather starting and reduced friction for better fuel economy.

But synthetics are expensive so synthetic blends are also available as a more affordable alternative. A blend obviously can't deliver the full benefits of a 100 percent pure synthetic, but it's certainly a step up from a conventional oil. You can also create your own "blend" by mixing one or more quarts of syntehtic oil with conventional oil when refilling your crankcase after changing the oil.

Motor oil can be recycled and re-refined, but it doesn't last forever in an engine. Heat, wear particles from the engine and combustion blowby contaminants all cause the additves in motor oil to break down as the miles accumulate. Because of this, the oil eventually needs to be changed. Auto maker recommendations can vary from the traditional 3000 miles up to 10,000 miles or more depending on operating conditions.


Some new vehicles do not even have a recommended service interval for changing the oil and filter. They use an "oil monitor" system to let you know when your oil should be changed.

Most oil monitor systems do not actually test the oil's condition (though some may use a sensor to measure oil conductivity to determine contamination). Most oil monitor systems estimate remaining oil life by tracking hours of engine operation, miles driven, ambient temperatures, time spent idling and other factors that affect oil life. Using algorithyms based on laboratory and field testing, the oil reminder system calculates how much oil life has been used and how much is left.

Under ideal operating conditions, the oil change light may not come on for up to 10,000 miles or more on some vehicles - but that's under ideal operating conditions only. Many vehicles operate under "severe service" conditions in regular city traffic. Severe service includes short-trip driving (seven miles or less, especially during cold weather), extended idling, towing a trailer or driving in dusty conditions.

What's more, the oil life monitor estimate is based on using a high quality oil - which may be a full synthetic or a blend, not a low quality mineral oil that may not go the distance. According to the American Petroleum Institute (API), over 20% of 1800 oil samples taken from quick lube bulk tanks around the U.S. are mislabeled or fail to meet viscosity or performance requirements!

The most commonly recommended interval for changing the oil and filter is still every 3,000 miles or three months if you do a lot of short trip cold weather driving, or you drive an older high mielage (over 100,000 miles) vehicle. If you drive a newer low mileage vehicle, and do a lot of highway driving, you can go 5,000 miles or six months with a high quality conventional or synthetic motor oil.

Many auto makers today recommend 7,500 mile oil change intervals, which is okay for newer low mileage vehicles using a high quality oil that don't spend a lot of time idling. But on some applications (notably certain Chrysler and Toyota engines), stretching the oil change interval to 7,500 miles has resulted in engine sluding problems and expensive engine repairs.

Just remember that opil life depends not only on miles and driving conditions but the type of oil used. Synthetic motor oils last longer than conventional motor oils, so the higher cost can be justified with longer oil change intervals. Some suppliers of synthetic oils claim their products can go up to 20,000 miles or more between changes. We would NOT recommend trying to go that long without and oil change in spite of what they claim. The best advice is to follow the service guidelines in your owners manual.


A wide variety of aftermarket oil and crankcase additives are available that may provide various benefits for your engine. Most auto makers say crankcase additives should not be necessary as long as the motor oil you use meets the auto maker's warranty requirements. However, for older high mileage vehicles many additives can be quite useful. These include oil additives that reduce oil burning and leakage such as STP, Casite and others. These type of "motor honey" additives can help reduce oil consumption and help quiet noisy valve lifters. Some also contain zinc/phosphorus anti-wear additive, which is good for flat tappet camshafts and lifters. There are also additives to reduce friction and wear, and cleaners for removing sludge from the crankcase in neglected engines.


The proliferation of new electronic automatic transmissions and CVT transmissions in recent years has created the need for specific automatic transmission fluids for specific vehicle applications. What's important here is to make sure the ATF you buy is the correct one for your transmission. Use the wrong fluid and it could damage your transmission! If you are not sure what type of ATF to use, refer to your vehicle owner's manual or the marking on the transmission dipstick filler cap.


For manual transmissions and differentials, a single 80 or 90 weight gear oil or a multi-viscosity gear oil may be required. But many manual transmissions, transaxles and power steering systems specify ATF for lubrication. Some vehicles that have limited-slip differentials require a special type of oil for the clutch packs.

CV joints require their own type of grease (never ordinary chassis grease), but U-joints can typically operate just fine with chassis grease or multi-purpose grease. Wheel bearings always require a high temperature grease.

Other special lubricants that may be required for certain jobs include: moly-based brake grease for lubricating calipers and shoe pads; silicone brake grease for lubricating caliper and wheel cylinder pistons and seals; white lithium grease for lubricating door hinges, cables and other sliding mechanisms; dielectric grease for lubricating and protecting spark plug boots and electrical connectors; and anti-seize for spark plugs, oxygen sensors and fasteners.

motor oil More Motor Oil & Engine Lubrication Articles:

New Motor Oil Specifications 2014

What Every Motorist Should Know About Motor Oil

How Often Should You Change Your Oil?

How To Change Your Oil

Oil Filters

Certified Master Technicians Speak Out On Oil Change Intervals

API Motor Oil Classifications

Motor Oil Additives

Motor Oil Viscosity

Synthetic Motor Oil

Troubleshooting Low Oil Pressure

Oil Pump Diagnosis

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