The Auto Channel
The Largest Independent Automotive Research Resource
Official Website of the New Car Buyer

Feature Story


by Bob Hagin

December 04, 1998

For those readers who remember, the corner gas station used to be more than just a place to fill the tank. It was almost part of the family. These days, the "service" station is almost a thing of the past. Where once an attendant checked the fluids (oil, coolant and in even earlier days, the air in the tires), now the "fill-up" is often done by the customer and in states where that's illegal ( Oregon, for instance), the employee who pumps the fuel does that and nothing else.

So unless drivers stick to factory-recommended maintenance schedules, they have to take care of their vehicular liquids themselves. So to keep your car or truck moving along smoothly, here are the fluids that need to be checked or replaced regularly:

FUEL - Unless you're driving one of those new electric Hondas, Toyotas, Fords or GMs, you have to put fuel in the tank or your machine won't run. I've never been convinced that higher octane gasoline gives a driver any advantage - unless the vehicle is a hot performer. The owner's manual tells what octane fuel works best, but it's been my experience that from state to state and in some cases, even from town to town, the octane rating is sometimes not exactly as given on the pump. A satisfactory octane number in one county may cause pinging in another. Since gasoline and diesel fuel will both absorb a certain amount of water from the atmosphere, it's best to keep the fuel level high in order to keep water contamination as low as possible.

MOTOR OIL - The oil in your engine not only lubricates all the moving parts but it operates internal parts such as the hydraulic valve lifters and, in some cases, the tensioner that adjusts a camshaft timing chain. I've always felt it's better to change the motor oil (and its filter) about twice as often as the factory recommends, since oil is cheap compared to replacing an engine. The oil also cools the internal parts and if the level run low, those parts (bearings, pistons, camshaft etc.) tend to run hotter. The label on top of an oil can indicates its recommended use and roughly speaking, the higher the letter designation, the better.

TRANSMISSION FLUID - In a manual transmission, the liquid that does the lubrication of the gears and hubs is called an oil and unless it leaks out, it lasts a long time. Many manufacturers recommend that it never gets changed, but changing it ever couple of years couldn't hurt. The same is true of the oil that lubricates the differential gears. But the fluid in an automatic transmission is much thinner, more complex in its composition and needs to be changed (along with its internal filter) every couple of years. As the mileage on the vehicle rises, it's a good idea to have the automatic transmission flushed since the torque converter (which holds a lot of fluid) can't be drained.

COOLANT - If the radiator needs fluid, it should be at least half water and half antifreeze with an even higher percentage of antifreeze for colder weather. Besides keeping the engine from freezing, the antifreeze lets the engine run cooler in hot weather and helps protect the cooling system innards from the corrosive action of electrolysis. By the way, the water should be distilled, but few people use it.

HYDRAULIC BRAKE/CLUTCH FLUID - The fluid that operates your brakes and sometimes your clutch is usually made of mostly glycerine, but some systems use a silicone-based formula. They shouldn't be mixed. The fluid should be checked occasionally and if it goes down, it most often means the brakes are wearing out. The only other possible source of brake fluid loss is a leak (very bad) so it should be checked often. Some manufacturers like Honda and Acura recommend flushing the hydraulic brake system periodically. My grandson didn't and he wound up having to have a new (and expensive) brake master cylinder installed on his Acura.

WINDSHIELD WASHER FLUID - A windshield that's covered with a dirty mist is tough to see through and a driver needs all the help possible - especially when dirt-laden water or snow is splashed up. Windshield washer fluid can be plain water but the minerals in it can obstruct the small passages. They're hard to clean out and in some cases, the nozzles have to be replaced. Washer fluid is not expensive - a gallon bottle makes 16 gallons of fluid and costs about $10. The system should be used occasionally just to keep it from getting plugged up.

FUEL TREATMENT - There are several fluids on the market that you put in your fuel tank to keep it free from water and to keep your carburetor or fuel injection system clean. In the case of a diesel engine, an additive can keep some really dangerous bacteria from forming in the tank. You don't have to go overboard, but a few ounces of the stuff in your tank every couple of months should keep water contamination at bay.

ELECTROLYTE - Electrolyte is the liquid that's in your car's battery and it's made up of 70 percent distilled water and 30 percent sulfuric acid. If the electrolyte level in your battery can be checked (and unfortunately it's not possible in most modern automotive batteries), you only have to be able to see the top of the fluid for it to be OK. If the fluid level goes down more than an ounce in a thousand miles, something is wrong with the charging system.

Keeping your vehicle on its liquid diet shouldn't be too hard, but if you don't, it may take some surgery to get it back in shape.