Checking oil, when hot or cold?
 

I have never given this much thought before and maybe there isn't much difference, but when should one check the oil level?

It dawned on me that for transmissions and power steering fluids, there is a "cold" and "hot" level. Obviously when these fluids get hot, they expand, hence the different level marks. Does this apply to engine oil?

I have always been in the habit of checking the oil when the engine was cold. My theory is that when I do an oil change, I put in "x" amount of cold oil. Also with the engine being cold, I knew that all the oil was in the pan. Yet, every owner's manual for every car I have had says to check the oil everytime you get gas, ie; when the engine is at operating temp.

Again, maybe there isn't much of a level difference. Just thought I would pose the question. I suppose for the purposes of tracking oil usage, that it doesn't atter as long as one checks the level at the same time ie; cold or hot.

Thoughts

I check,trans,and oil hot.Radiator when cold.To much oil can blow seals.

+1

Check engine oil when hot but about 5 min after engine has been turned off to let oil drain back into pan. Many organic liquids expand and contract with temperature.