About 25 years ago I bought a lot of RV type Onans from the Western Canada Distributor, to power instrumentation I was building. Everything about this company was first class: big inventory, good repair service and lots of dealers. My next contact with Onan was at Cummins aboiut 10 years ago and the inventory and service sucked big time. I couldn't find anyone at the local Cummins shop who had any interest in Onan. Since the former distributor lost most of his Onan business in the sale, he was retained as a dealer.
Since then, I go to the dealer and let him fight with Cummins. In my last contact, they were unable to supply two pistons that were the same siize and had the same ring groove. I ended up rebuilding an engine with a mismatched pair after multiple trips and returns to Cummins. As to parts cost, my little pistons for a 20 HP Onan cost 70% more than the pistons for a 400 HP Cummins. Personanlly, I think Cummins really spoiled a good company.