My oil is "full" when the engine is hot and a little low when cold. Which is correct?

 

The manual says to check it hot. But now that you know what it looks like cold (compared to when it is hot), it is easier to check it first thing in the day before you start the car (ie. cold).
ps. If you check the oil correctly, the difference between hot and cold readings should be no more than about 1 "X". If it is vastly different, then you are using a procedure (sequence of steps) that can be improved.
pps. 1 "X" is nothing to get too worked up about.

 

I've always checked my oil roughly 15 minutes after I shut down the engine.

I'm not sure if that's right though.

Besides, my readings are usually consistant enough no matter when I check the oil.

 

 

This is perfect!
On a HOT engine, you only need a few minutes as the oil flows really well. If the engine is still cool, it may hang up a bit, like if you just started the car, moved it out onto the driveway and shut is off.
The consistency you see is the way it ought to be.

 

The high and low marks on dip sticks are set for "hot" readings. However, this does not mean that you should shut off your car and immediately check the oil. If you shut off your car and immediately check the oil, a measurement taken 10-15 minutes later may be higher. In some cars the difference is insignificant. In others, it can be quite significant. Take my Altima for example. If I shut it off and check the oil, I will get a particular reading. If I check it 15 minutes later, I will get virtually the same reading. If I check it when it is cold, I will get virtually the same reading again. Contrast this with my Pathfinder. With the amount of oil it has in it right now, if I shut off the engine and immediately check the oil, it will read right at the low mark. If I check it again 10 minutes later, it will read right at the high mark. If I check it when cold, it will be about in the middle. Oil measurements taken 10-15 minutes after the engine is shut off can be higher because some engines take longer for the oil to drain down to the pan. Also, the shape of the oil pan and the quantity of oil can effect how the oil's expansion and contraction due to temperature read on the stick. So, the bottom line for any car is check the oil on a level surface 10-15 minutes after you shut it off. If by checking the oil immediately after you have shut off the car or when the car is cold, you are able to determine that the is no difference or the difference is consistantly measurable (like my S2000 is always 1 X lower when cold versus 10 minutes after shut off hot), then it's OK to check it those times as well.

 

Thanks for the input. Mine is about 1 "X" low when cold, full when hot, so it looks like my readings are consistent with what they should be.

 

my engine oil level is always lower when the engine is warmer, this probably means all the oil did not have a chance to go back to the oil pan.


that is why i check it first thing in the morning before i start the car.