Recomended oil for Onan 4KW generator

What ericsmith32 said in post #5.

15W40 is probably the hot tip if you are going to be using the generator underway due to the increased temperatures under & around the RV.

While you can use a diesel 15W40, I'd suggest getting the real deal by Onan. Or an oil engineered for aircooled motors. Aircooled engines require a different additive package than diesels. Change the oil by the Onan schedule.

I used to buy nothing but Onamax which then was 15-40..I bought it by the case and have some left over but it is so old that I decided not to use it so I took the bottle down to the parts store and matched the services and got 10-30 which I think Onan is recommending now.

rjstractor wrote:

tpi wrote:
Onan manuals are always an interesting read. There is an Onan standby generator using our Ford V10. 15W40 oil is recommended, and 5W30 is only recommended to 50 degrees F. FWIW they also call for cylinder head rebuild at 1000 hours (or two years whatever first) on the V10. 1000 hrs. translate to 30,000 40,000 miles of typical driving? Ummm don't think I'll be pulling the heads..

A stationary generator application is a completely different duty cycle than a vehicle, so I wouldn't think you could even translate hours to miles driven. It would be interesting to see how many hours the V10 would run in a generator application.

It would be.. Of course the generator applications could be as variable as miles driven. Generator doing a lot of 80-100%. Or mostly 30-50%. Or short test runups. Generator at hot standby, or not. Still when airport shuttle V10s have gone over 500,000 miles (think of the hours here) and they pull heavy motorhomes along for 160,000 miles or more I would question whether a cylinder head would be worn out at 2 years/1000 hrs whichever occurs first. Especially if compression and oil consumption measured good. These engines in generator duty are running 1800 RPM, turbocharged, and putting out about 170 HP maximum-conditions which may or may not be harder on certain parts of the engine vs. automotive applications.

15W 40 Also,mainly because when I need to use it to run A/C the outside temp in the desert is very high.

It is also what Onan recommends for this application.

Because of the temperatures at which I operate the genset, I use 15W40, Delo or Rotella, whichever was available or less expensive when I picked it up.

The Logans wrote:
Which brings up another question, has anyone ever added a temperature gauge to the Onan 4000? Love to have one in the driving compartment...

Temperature of what on the generator--cylinder head, oil, exhaust gas, ambient temperature around the generator, or...? Obviously there's not really a need for a water temperature gauge for an air cooled engine that has no coolant water.

tpi wrote:
Onan manuals are always an interesting read. There is an Onan standby generator using our Ford V10. 15W40 oil is recommended, and 5W30 is only recommended to 50 degrees F. FWIW they also call for cylinder head rebuild at 1000 hours (or two years whatever first) on the V10. 1000 hrs. translate to 30,000 40,000 miles of typical driving? Ummm don't think I'll be pulling the heads..

A stationary generator application is a completely different duty cycle than a vehicle, so I wouldn't think you could even translate hours to miles driven. It would be interesting to see how many hours the V10 would run in a generator application.

Which brings up another question, has anyone ever added a temperature gauge to the Onan 4000? Love to have one in the driving compartment...

nadsab wrote:
Great thanks.

Just curious - if the oil is low, or generator too hot, will it automatically shut down after running for an hour or so?

Yes

I use what is specified in the owners manual with regards to viscosity. But I can't recall off the top of my head what that is. I recall it is a straight-weight oil. Given we don't camp in winter, our see no reason to deviate.

I use full synthetic in our 2007 Onan 4000 because synthetic does not burn as easily as conventional oil. So if there is an oil-burning condition, the full synthetic provides me a little more safety margin. If a catastrophic failure occurred, for example the oil drain plug is loose and falls out, the residual coating of full synthetic will provide a little more lubrication while I am wondering why my generator got clanky and decide to turn it off.

If you wonder, the answer is "NO", that did NOT actually happen to me.