Checking Generator oil question

[Mr__Steve]

Hello! I have an onan 5500 gas generator in my motorhome. A question that has always bugged me, when checking oil, when I unscrew cover and look at level it's always lower than when I screw it back on and check levels again. Which one is correct? I do check oil cold. Thank you.

[STBRetired]

My 5500 Onan behaves exactly like Mr. Steve's. Both my 4000 Onans show way overfull when you initially pull the dipstick. Maybe because the 5500 has an oil pump and the 4000s are splash lubed?

[Lynnmor]

Dave H M wrote:
I have a lawn tractor that is just the opposite. Oil is always up on the stick when the cap that has the stick on it is first loosened.

I have four Onans and they all do that.

[Dave_H_M]

I have a lawn tractor that is just the opposite. Oil is always up on the stick when the cap that has the stick on it is first loosened.

I do it two ways. one wipe and restick it or two loosen the cap a little while doing other checks and then come back to the dip stick last as allowing air to enter the top of the tube allows the oil to subside to a true reading.

[Mr__Steve]

Thank you, I have been trying to figure that out for since time.

[STBRetired]

The second one. Trapped air in the chamber where the dipstick is could prevent the oil from coming completely up to the true level on the dipstick. Removing the dipstick allows the oil to come up to its true level.

[rrupert]

Most engines should have the oil level checked when cold.