Oil for onan 2500 lp

Your manual probably says how much. Usually, RVs have a notebook with all of the component manuals. Mine uses a qt, but it’s 15 years old. I think they changed them a few years back.

Btw, I started running synthetic in mine. It got rid of some of the noise and since it was only a qt, wasn’t expensive to use compared to conventional oil.

I don't want to go dig out my manual but I'm pretty sure my 2 year old Onan 2500 uses less than 1 qt. I think they called for full synthetic so this is what I bought and run. I'd never seen purple engine oil before. LOL

Its .63 quart. Your oil bottle should have measurements on the side. I just buy regular 15w40 weight quarts for the Onan generators, makes it easy to measure the pour.

I've had both the Onan 4K and 5.5K units and never measured the oil while performing maintenance, just fill to the oil stick inlet. I know it is not very much oil with either unit, we always use full synthetic as it rarely takes more than a quart. Onan manuals are readily available online as I have downloaded them in the past, never had need to peruse through them, just like having manuals for all onboard equipment handy should issues arise.

I use the urine measuring pee cup that I had left over from my bout with kidney stones..
It is very accurate.
And quite handy!!

WalMart kitchen/home department will have a quart bottle with graduations on the side.
Rotella T6 15-40 in everything.

Sagebrush wrote:
Its .63 quart. Your oil bottle should have measurements on the side. I just buy regular 15w40 weight quarts for the Onan generators, makes it easy to measure the pour.

There are many ways to deal with this:
1. Guess. It's not that critical. The engine is not going to blow up if you put in .64, .65, or even .7 quarts.
2. Measuring cups. Your local dollar store carries cheap measuring cups marked in fluid ounces. .63 of a 32 fluid ounce quart is conveniently just slightly more than 20 ounces. Two 8oz cups and a 4oz half cup, and you're there.

I wonder why I have been dumping a quart of 15w40 in after I change it once a year since 2011 and also on my 2008 Lance. Back to the manual to see were I read 1 US quart.

Bottom line, they're just a little splash lube engine not unlike any other small engine.
Not alot of experience with them save for the 4000 in our new camper, of which the dipstick is useless. Fill it up like an old Briggs & Stratton.
Oil type, been using dino 15W40 or 5W40 in virtually every 4 stroke engine in the stable for many years. Buy it by the case on sale. Mowers, generators, old Jeep, small block and big block chevys, diesels, Chrysler Hemis (6.1 and 6.4) and the bikes. Bikes get T6 syn as it's wet clutch rated.
Only vehicle I don't use 15W40 in is the boy's 4.6 Triton Mustang. Maybe old wives tale, but told oil galleys are small many years ago when these engines were current and that they don't like anything but lightweight oil. So it gets 0W20.
Occasionally I'll use syn 5W40 or 15W40 in the other stuff if I have it laying around and don't want to go to the store, or it's on super sale or I think, know I'm going to extend the OCI past recommended.


The point is, it's largely not about the type of oil, it's about proper maint intervals.

When you see smoke pouring out the exhaust you know its over filled.... Don't do that. :)

Onans that I've seen all approve of 15w40 oil, but the small single cylinder Generacs say 10w30 weight is the max. At least the ones I've worked on. I buy quarts anyway so I put in what the service manual calls for.