Lately there has been a lot of discussion in the media on the topic of changing oil, specifically on how often it should be changed. It is my intention to convince my readers to change the oil in their vehicles every 3,000 miles. Let's first discuss the working environment inside the four-stroke internal combustion engine where the oil must do its job. The major environmental conditions which the oil must deal with are friction, intense heat, and contaminants (makes working on a chain-gang look easy).
Friction: Friction comes from hundreds of moving metal parts rubbing against each other. This creates intense heat and pressure which would destroy the engine in a very short period of time. The oil's job is to provide a lubricating film between the moving parts of the car's engine to decrease the friction and its negative effects.
Intense heat: In water-cooled or air-cooled engines, approximately 60 percent of the cooling is achieved by water or air. The oil performs the rest of the cooling function. As it circulates rapidly through the engine at 50 to 70 pounds per square inch pressure, the oil carries heat away from the camshaft, rods, pistons, and valve train. It is then circulated in the lower structure of the engine, where it is mixed with cooler oil. This oil was cooled by air passing over the crankcase, which is also known as the oilpan.
Contaminants: Contaminants can build up in the car's engine in the form of soot, ash, acid, and moisture. This results in dirt in the form of sludge, varnish, and resins that become baked onto engine parts and interfere with proper performance and oil flow. The motor oil in the car's engine has a detergent built into it that disperses the dirt, keeping it suspended within the oil until its either filtered or drained away when it is changed.
In addition to these environmental conditions that the oil must deal with, the oil performs other functions. To the naked eye, the piston rings and cylinder walls of the engine appear perfectly smooth. But they are not. Under microscopic examination, a large number of "hills and valleys" appear. These impressions provide an escape route for vapor and gases during the compression and power stroke of the engine. If it occurs, this is called "blowby," and results in the engine losing power. These gaps must be sealed up by the oil to prevent "blowby."
In summary, the demands made on the oil are very "draining" (no pun intended). The oil eventually loses its ability to lubricate, clean and flow freely. Each function is extremely important to the performance and life of the engine. Changing the oil every 3,000 miles is "cheap insurance," with an extremely high cash value. Which do you prefer? Oil changes at $19.95 every 3,000 miles, or an engine replacement every 40,000 to 50,000 miles at $3,000 to $5,000.
