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Checking Generator oil question

Mr__Steve
Explorer
Explorer
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.
6 REPLIES 6

STBRetired
Explorer
Explorer
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?
1999 Newmar MACA 3796 F53 6.8L
2016 Ford Edge Sport
Roadmaster Sterling A/T with Brake Buddy Select

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

STBRetired
Explorer
Explorer
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.
1999 Newmar MACA 3796 F53 6.8L
2016 Ford Edge Sport
Roadmaster Sterling A/T with Brake Buddy Select

rrupert
Explorer
Explorer
Most engines should have the oil level checked when cold.
Rich and Joyce
2018 Jayco Jay Flight 21QB
2012 Ford F150 4X4 Supercrew EcoBoost
Reese Strait-Line Dual Cam Hitch

Amateur Radio K3EXU