Oil for Onan 8 KW generator

[Bear43C]

I need some advice. I just purchased a 1995 43 C. The previous owner used straight 40 weight for both the 6V92's and the Onan generator. The oil fill cap on the generator states use D10W-30. What oil do you recommend?
Thanks,

Bear43C

[SeaEric]

My mechanic advised me to use 40w for the DD's and 30w for the Onan.

[carolinacoast]

We have stuck with the prior owners philosophy and run Delo 100 40wt in the same engines, 2 gens(onan & kubota) and the transmissions. 1 oil on the boat for everything. A heavier oil in the gens might be an issue in colder climates for starting the gen, but not in the southeast.

[bostonhatteras]

My Genset requires 15w40. Being a 4 cycle you have the option of getting the latest additive package oil available. Is it cj 4 now? or use the same as the mains and have one less container of oil taking up space!

[Avenger]

This is going to sound obnoxious, but why don't you RTFM?

That's an acronym for Read The Manual.

The manufacturer knows what oil is correct for the engine. SAE 40 may well be acceptable for that application. But if it's not why risk the cost of replacement for convenience?

Not trying to be a,.... ahem... "breaker" here but there's a million opinions to be had for free. When the rings fall out of the thing, you'll be the one getting the invoice.