Changing oil regularly -- yourself -- can save hard cash

Want to save a lot of money on maintaining your car? That's easy. Change the engine oil on a regular basis -yourself.

Basically, the major function of motor oil is simply to lubricate the moving parts of an engine. But beyond this, the oil also cools the engine, helps keep the engine clean, and protects the metal components from corrosion.

How often to change the oil? Some automobile manufacturers recommend an oil change every 7,000 miles, but remember, this is only under ideal driving conditions. Experienced mechanics, on the other hand, often recommend an oil change every 4,000 to 5,000 miles or four to five months -- whichever comes first.

If you do the job yourself, you can buy the oil, filter, and grease at major department stores, often on sale, or at discount auto supply stores for less money than a service shop charges.

The car owner's manual provides the best information on the proper viscosity, or thickness, of oil for your car, depending on the season of the year.

Stay away from oils with a paraffin base. As a rule, the major oil companies use highgrade crude. If you're not sure which is best, ask an experienced mechanic.

Should you use an additive? John D. Fobian, director of the American Automobile Association's (AAA) automotive engineering department, says, "Modern lubricants contain all the additives and properties neces -sary to gain satisfactory performance from cars. These aftermarket additives are just an extra dose of the same chemicals which petroleum companies use in their products to begin with."

If you plan to change the oil in your car, do the job right.

Almost as important as the oil itself is the oil filter. The primary function of the filter is to remove any abrasive particles, such as dirt and sludge, from the lubricant.

Replace the filter each time the oil is changed, engineers recommend. There is little advantage to putting clean oil into the crankcase if the oil filter is dirty. The new oil will then become contaminated or the dirty filter can even restrict the flow of oil to the engine.

After changing the oil, you may also want to perform a "lube job" on your car as well as check the fluid levels in the transmission and differential.

Here are some of the tools you'll need: a grease gun with a cartridge of all-purpose grease; heavy-weight differential oil (the differential gears compensate for the difference in rotational speeds of the rear wheels while the car is turning); a socket wrench the size (usually 3/8-inch) of the plug located on the, back of the differential (the differential is in the center of the rear axle of the car if it's a rear-wheel drive; front-wheel-drive cars don't require this service); transmission oil; a suction gun or kitchen turkey baster (the baster is much less expensive) for adding fluid to the differential and transmission (if the filler is under the car); clean rags; a long box-end wrench to fit the oil-pan drain plug located on the bottom of the engine; a two-to five gallon shallow pan; and an oil-filter wrench.

You also will need to find a relatively flat area on which to work on your car.

Run the car for a few minutes to heat up the engine oil so it will drain better.

Block the rear wheels and jack up the front end of the car far enough to allow sufficient clearance so that you can move around freely underneath. Be sure the jack is secure. Put jack stands under the frame for primary support.

Spread out newspapers under the engine to catch any oil that may spill accidentally.

Place the shallow pan directly under the oil-drain plug. Get the plug wrench and a rag. Slide in under the engine head-first and make yourself comfortable. Place the wrench firmly and evenly on the plug in a position for good leverage. Loosen the plug until you can turn it with your fingers. When loosening the plug , maintain steady inward pressure on it and keep your arm up and out of the way. Once the plug pops off the oil will flow out. Be careful not to let it splash onto your skin because it could be extremely hot.

While you let the oil drain, locate the old oil filter and remove it (use the filter wrench if it won't loosen by hand). The filter is usually located several inches above the oil-drain plug on the engine side.

Remember, there's oil in the filter so make sure the pan is under it so as to catch what spills out. Drain the filter into the oil pan.

Dip your finger in some of the new oil and rub a light film onto the rubber seal of the new filter. After you make sure the filter mating surface on the engine is clean, screw on the new filter until the seal meets the flange. Rotate it to snug it up as directed on the filter carton.

Don't forget to put the oil plug back in! There are too many stories of mechanics who put in six quarts of oil only to discover they've formed a clean six-quart pool of oil beneath the car.

Also, check the plug to see if the copper gasket is still on it. If not, the gasket may either have stayed on the flange at the drain opening or it could have dropped off into the drain pan. If you can't find the old one, you should get another one to prevent the oil from leaking out around the plug.

Look in the manual for the engine oil capacity. If it's four quarts without the filter, start by putting that much in the car. Pull out the dipstick, wipe it dry, replace it, and then remove it again to check the oil level. Add oil till it reaches the proper level.

What do you do with all that dirty oil?

Ask some repair facilities or service stations if they have drums or tanks where you can get rid of it. If you can't find a disposal site, call one or two local heating-oil companies, or even your local sanitation department, and ask about safe dumping areas for oil.

Above all else, do notm dump waste oil on the ground or down the kitchen drain (some people do). It's an environmental hazard and should be disposed of properly.

While the car is still up on the jacks, lookfor the grease fittings (a small round knob with an orifice at the tip) on the suspension and steering components located between the front wheels. Sometimes the universal joints (hinge arrangements connecting the driveshaft to the transmission and to the differential in the rear) have fittings on them.

Grease these points at the first interval recommended by the manufacturer -and then every oil change after that.

Wipe off the fittings with a rag. Then push the grease gun securely and straight onto the fitting. Maintaining an even pressure, pump grease until it emerges from the joint. If there is a rubber "doughnut" at the fitting, stop pumping when the "doughnut" begins to expand.

If you have a late-model car, you may not even find grease fitings because there aren't any. A dealer or mechanic can imform youabout servicing these parts.

You also can check the fluid level of the transmission. Manual-transmission cars usually have an oil-filter plug on the side of the transmission just behind the engine. After removing the plug, the oil should start running out the hole. If not, add transmission oil, using the suction gun or turkey baster, until it begins to overflow. Then replace the plug.

Next, lower and remove the jack and slither in under the rear end of the vehicle to check the differential. Remove the plug and use your finger to see if the lubricant level is up to the lower edge of the opening. Add lubricant until it begins to flow out the opening. Immediately replace the plug.

Run the engine for a few minutes and make sure that either the oil-indicator light goes out or the oil-pressure guage gives a proper reading within 30 seconds. If not, turn off the engine immediately. If you cannot locate any obvious mistake on your part, call for a mechanic.

With the engine running at idle, check the automatic-transmission fluid level if applicable to your car.

Assuming the oil pressure is fine, turn off the engine and in a few minutes check the oil level again. Add another quart if the level is near or below the bottm mark on the dipstick.

To complete the job, apply grease to the door latches, hinges, and self-adjustment tracks. Squirt some oil on small moving parts, such as the carburator link-age, glove compartment hinges, and other inside gadgets on the car.

Pro-fessional mechanics at independent repair shops and automobile dealerships are usually able to provide advice.