UOA 11 year old oil and follow up UOA for LP Onan RV generator

Aug 3, 2015
Onan KY 3600W 3600RPM generator. Purchased RV from original owners.

"Here are the manuals." Opening up the generator manual I was surprised they had filled out the "maintenance or service performed" section. But wait: it looks like they only did two oil changes in the first two of 13 years of ownership. (Break in oil change at 20 hours and one change a year later with 63 total hours on the set. RTFM also says to change the oil every year regardless of hours.)

"Did you log oil changes elsewhere?"

"It doesn't have enough hours to change the oil."

Yeah, confirmed the oil wasn't changed since. Oil was 11 years old with 53 hours on it.

So I did an immediate oil change, took a trip with it, and did another oil change with 28 hours on the oil.


It has taken four oil changes for the wear metals to quit being flagged on my UOA. Valvoline straight 30 weight oil used except last sample. I have since switched to 10W-40 as I have been caught camping at altitude below 32F and have oil carryover problems in our 117+ extreme heat. (Did the TSB for oil carryover into the air cleaner after these oil samples.) I will likely switch to 15W-40.

Note: 1/5/19 was 274 hours and 47 hours on oil.


Old brand change, Quaker State, and sodium is now way down.

Seems the numbers were Break in wear products. Nor a whole, lot of hours and probably the high iron could be corrosion from sitting. Sodium from the add package.