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Check the Oil

Written by Earl Gautsche

Few people know that the engine oil temperature is actually hotter than the engine coolant. Typically, the engine coolant will run between 190 and 210 deg F, while the engine oil typically runs between 220 and 240 deg F. It is normal for some oil to be vaporized at these temperatures.

When the piston moves downward in its cylinder, a thin film of oil is left behind on the cylinder wall. During the power stroke, this oil is consumed in the combustion process. This is true even for engines with piston rings in excellent condition.

As a result, varying rates of oil consumption are accepted as normal in all engines. The accepted rate of oil consumption for gasoline engines can be in the range of one quart within 2000 miles on a properly driven and well-maintained retail vehicle. The rate of oil consumption for severe duty vehicles, like police package and special service package vehicles may be higher, as much as one quart in 1500 miles.

Don’t think that you can go 2000 miles before checking the oil. In fact, checking the oil with every fuel is recommended. And only add oil with the “Starburst” symbol and an API “SM” rating.

Oil change intervals have changed. Nearly all GM vehicles produced today are equipped with the Oil Life System. This GM technology allows the vehicle to alert the driver when an oil service is needed. With this notice in the Message Center, the oil should be serviced within two tank fills, or 600 miles. With this system, the oil change interval will probably be extended to between 5000 and 6000 miles, and possibly more for admin cars.

In the past, with oil changes at 3000 miles, and a police-use rate of oil consumption of one quart in 1500 miles, the resulting low oil level (i.e., up to 2 quarts low) was remedied by the oil change.

Today, with greatly extended oil change intervals, you could be three or four quarts low by the time the Change Oil light is activated. This is enough to damage the engine. Most GM engines have a low oil light (Engine Oil Low, Add Oil) that activates when the crankcase is two quarts low. However, even Message Center lights are occasionally ignored. Checking the oil at every gas tank fill is more important now than ever.

Unnecessary Maintenance Expense

In normal use, GM vehicles do not require additional procedures or additives beyond what is presented in the vehicle maintenance schedule. These maintenance schedules do not call for the flushing of the engine crankcase, fuel injectors, air conditioning systems, radiators, transmission coolers, brake systems, or power steering systems as part of routine maintenance. Fluid flushing equipment for the above is specifically designed to aid and accelerate fluid changing when required as a part of a specific repair.

A common example of unnecessary maintenance expense is “fuel injector cleaning.” Under normal circumstances, this is not part of the required routine maintenance. If the “Service Engine Soon” light comes on, and after a complete diagnosis, an injection cleaning might be appropriate.

Another example is “crankcase flushing.” This is not recommended nor endorsed for any GM gasoline or diesel engine. In fact, some of the flushing chemicals may be incompatible with internal engine components and may damage bearings and engine seals. This damage is not covered by the powertrain warranty.

Finally, do not add any oil additives to the crankcase. The engine oil meeting American Petroleum Institute standards, and bearing the “Starburst” symbol, meeting GM Standard 6094M (non-synthetic, for gasoline engines), already has the exact additive package necessary for the engine. Failure to use recommended engine oil, or the use of additional oil additives may result in engine damage not covered by the warranty.

Earl Gautsche is the National Police Fleet Service Manager for GM fleet. He can be reached at (248) 789-4679.

Published in Police Fleet Manager, Nov/Dec 2005

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