Why do mechanics wipe off the oil dipstick and then put it in back in before taking an oil level reading?
When the engine is running, oil is slung around inside the crankcase and onto the dipstick. This could result in an incorrect reading. By wiping the dipstick clean and reinserting it, a more accurate level of oil is displayed. The engine should also be allowed to sit without running for two minutes before taking a reading. This allows more of the oil circulating in the engine to return to the oil pan and gives a more accurate reading.
