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BlueThunder4 · 07-10-2020, 09:50 AM

Quick question, had the wife pick up some 15W40 oil to do an oil change on our Onan 5500 RV generator. She got the right brand and weight oil but I see it says motorcycle oil on it. I have a lot of experience with engines but none with motorcycle engines, is this oil ok to use in the generator? I’m assuming it’s nothing more than additives included that make it designated “motorcycle” oil ie the wet clutch, high revving rpms, etc but will this be ok for the Onan?
Thanks

Mr_D · 07-10-2020, 09:56 AM

If it meets Onan's SAE specs then there should be no problem.

56safari · 07-10-2020, 10:04 AM

The motorcycle oil has lower ash content in the detergent and friction modifiers to help with the motorcycle's wet clutch operation and longevity. Both the differences go the wrong way for your use. Probably would do no harm, but i'd return it and get the correct 10w40.

sibe · 07-10-2020, 10:16 AM

Quote:

Originally Posted by 56safari

The motorcycle oil has lower ash content in the detergent and friction modifiers to help with the motorcycle's wet clutch operation and longevity. Both the differences go the wrong way for your use. Probably would do no harm, but i'd return it and get the correct 10w40.

Not bashing but a bit more info That oil is a MA2.. It has friction modifiers but limited for wet clutch use.. No biggie , no clutch in onanm but it does have good anounts of zinc and phos.. for metal to metal contact in flat tappet cams etc..

Low ash in motorcycle oil is generally for 2 stroke oils as not to clog rings or power valves,, or Cats on some .

I would use any motorcycle oil or diesel oil made for flat tapped in a genny before any generic oils or new energy saving modern car/truck oils..

Most MA/MA2 oils also are good for air colled or higher temp operation.. Gennys can run hard in 105 degree box they are in..

If you have doubt, go get a bottle of onan oil and smile..

EdInArk · 07-10-2020, 10:44 AM

Unlike other vehicles, most motorcycle transmissions are lubed by the same oil that's in the crankcase.

Motorcycle oil is designed to use with the constant mesh transmissions used in motorcycles. The viscosity improvers in some oils can be sheared by the transmission gears and reduce the viscosity over time.

I wouldn't hesitate to use it if it meets the specs required by Onan, and I think it does.

Bill Gail · 07-10-2020, 10:49 AM

There are numerous schools of thought on what oil to use in air cooled engines . Personally , I run Valvoline 20/50 Racing Oil with high zinc content in my generators and classic cars.
Designed for high loads , high rpm's , flat tappet cams and high heat from a racing environment.
My experience is excellent performance and reliability .

BlueThunder4 · 07-10-2020, 12:58 PM

Thanks all for the replies. I’ll check the specs Onan requires for oil, I have no problem getting more oil if this wouldn’t work but didn’t want to make another trip to the store if it wasn’t a big deal.

setaylor216 · 07-10-2020, 01:10 PM

I would think the Mobil 1 specific for HD air cooled engines would be the best choice if you Onan is air cooled.

EdInArk · 07-10-2020, 01:19 PM

Quote:

Originally Posted by setaylor216

I would think the Mobil 1 specific for HD air cooled engines would be the best choice if you Onan is air cooled.

The 15w40 motorcycle oil the OP is referring to is probably for a liquid-cooled, multi cylinder motorcycle. HD oil tends to be in the 20w50 range.

I'm not sure why I'm arguing, though. I still think it'll be just fine.