Checking Engine Oil Level
| 02 August 2002
Have you ever been a victim or have you seen someone else victimized by this old service station trick? In years gone by when there were still a lot of full service gas stations, a few of them had unscrupulous operators. Your car would no sooner stop at the gas pump than an attendant would appear at your window asking how much gas you wanted and did you want your oil checked. So you’d give your answers and, yes, you usually wanted the oil level checked. The unscrupulous attendant would open the hood before he started to pump the gas because it was important for him to get the dipstick out of the engine before all of the oil ran back into the oil pan. He’d pull the stick out, wipe it off, reinsert it, pull it out again and shake his head. He’d bring the stick to the window to show you that you were a quart or more low. If you didn’t know that it takes several minutes for all of the oil to drain back into the pan after turning off the engine, you’d tell the attendant to add a quart. A lot of people bought a lot of oil that they didn’t need in stations like that.
The moral of the story is that you should never check oil level immediately after shutting-off the engine. Wait several minutes for it to drain back into the pan because when the engine is operating, a lot of oil is doing its job up in the engine proper. If you’re checking your oil at the local “you-pump-it” station, do it after you pump the gas. Better yet, check it when the engine hasn’t been run in a while, like first thing in the morning before you start the car. And when you make the check, be sure the car is on level ground. If it’s on a slope, the reading won’t be accurate.
Something else to consider is the age of the car. Older cars have a dipstick that says min and max or at least there’s a mark for min and max. Immediately after an oil change, when the correct amount of oil is in the engine, it will read at the max indicator. It’s only necessary to add oil when the level reads at or below the min indicator. On newer cars, the dipstick may have a crosshatched area. The engines in those cars usually indicate about half way up the crosshatch when they have the correct amount of oil (e.g.: immediately after an oil change); i.e., they don’t have to indicate at the top of the pattern to be considered full. As with the older type dipstick, add oil only when the level is at or below the crosshatch pattern.
One other precaution should be mentioned: never add too much oil to an engine. In other words, the oil level should never be above the max indicator on the dipstick. Too much oil can lead to aeration (bubbles) caused by direct contact between the oil in the pan and the rotating crankshaft assembly. Aeration can lead to engine damage because oil bubbles don’t lubricate nearly as well as a uniform film of oil.