Two comments.
First, the 2800 (or 2500 if yours is a propane genny) is the ONLY unit in the Onan lineup with a small wrinkle in the oil fill details.
All the OTHER units, one uses the oil fill dipstick marks to determine the correct fill line. But, for the 2800/2500 one is to fill the oil to the top of the fill hole. The fill hole is angled a bit, but, you fill it right up to the "lip" - and yes that's higher than the full mark on the dipstick. If you look carefully in the Onan literature, Onan says to do this - rather than it being an "old wive's tale" or "street smarts".
I'd guess that some Onan dealers may not be aware of that little detail - but ours sure did know about it.
Since I've filled ours by that "rule", I've never had another failure (shutdown) - parked, driving, whatever. 'Tis like magic.
And, though the Onan literature recommends an oil change every 150 hrs, ours is always changed every time we change the Chevrolet engine oil. It's up in the air, 'tis easy to do, and the genny seems to like fresh oil.
Second, if you're spending some money at Cummins/Onan, you might look into the "Cummins Power Club" (www.cumminspowerclub.com). A $15 annual fee gets you 10% on parts and labor at participating Onan dealers. And, you can "join" after the work is done but before you pay the bill.
When I learned of it, the Onan dealer here pointed me to it when he saw what my bill was. Bill of about @250 - but spend $15 to save $25. Not to difficult to figure that one out.
Cheers.