Can you put diesel oil in a gas generator?

While I am sure you can use diesel oil it is usually 15-40 and most gas generators call for 30W or 10W30 oil. The diesel is good oil and will not hurt the generator in warm weather but if you are in cold temps it would be better for the engine to use a lighter weight oil. JMHO

Check the oil spec for the generator...as long as you choose an oil of equal or higher standard, you will be fine.

Diesel oil is typically holds a higher end spec and will cause no problem in a generator. The other way around usually doesn't work.

Diesel oil has additives specific to diesel engines including specific to the catalytic converter used on automotive diesels. Rotella now makes oils for gas engines with different additives.

Yes in the recommended multi-viscosity for all the temperatures you plan to cold start it in or high temperatures you will run it at high loads.

The viscosity for temperatures will be shown in your manual.

Engines experience a high % of their wear from cold start to close to operating temperature - lubrication is critical on cold start.

My ONAN is a diesel Kobata, it takes the same oil as my Cummins.

Not only is it OK some guys who build engines for a living will recommend it.

I run Delo 15/40 in my Onan genny.

I have run Rotella 15-40 (T4) in everything from my lawn mower to a 15 liter diesel without any issues. Usually diesel motor oil will have more detergent in it then oils that are recommended for gas engines.

Please clarify what you are asking.

If you mean diesel fuel in a gas generator, the answer is no.
If you are talking about the engine oil, it's always better to use the specific oil recommended by the manufacturer.

If you mean engine oil, the answer is yes.