*how* to check your oil?

[Pauloil]

I haven't driven into a Jiffy Lube or any other joint like that in over 10 years. I'd say most of the places recruit their employees from group homes or parole reporting centers.

+1 I know this is so....

[jimmy57]

OK,
THE proper way to check the oil level is to run engine until engine has been at normal operating temperature for more than ten minutes to get the oil temperature to a stable hot temperature. Then turn engine off while parked on level ground and wait ten minutes for draindown from upper engine. Cold temp varies seasonally but stabilized normal operating temp is pretty consistent. Also the level of oil when it is at the temp it will be when engine is running is what is important.

The oil level is not checked cold as the oil warms up and expands.
The oil is not checked running as the splash will give variable and inaccurate results.
The wait time will give you the most accurate reading as the oil will run from upper engine and from hydraulic tappets on 99 and older models for several minutes.
Overfilling allows oil to foam from being whipped by rotating parts. Foamed oil overwhelms the crankcase breather box capacity to condense the liquid from vapor and leads to oil consumption when there is no other reason other than overfilling.
Auto transmissions need to be running so the torque converter is full. Auto transmissions need to be at operating temperature for most accurate measurement as the ATF expands when hot and the large quantity of fluid used in transmission will result in a significant level change from cold to hot oil.
If you choose to check your engine oil level when cold for convenience or habit then do not fill the top mark, leave it at least a 1/3 way down.