I know an oilfield welder who has had 2 SA-250`s, with the Perkins motor. He was good at changing the oil on time and doing whatever routine maintenance is involved to get the most life out of an engine,and he sold the first one when it had 12,000 hours on it, and never had to overhaul the motor. The guy he sold it to said it is now up to 14,000 hours and still going,no overhaul. The second SA-250 the oilfield welder has is up to 8,000 hours and going strong. When I bought my Classic 3 from a 798 pipeline welder,he said he was just over hauling his SA-200 gas welder,and it had 10,000 hours on it,real good for a gasoline engine. I also bought a Vantage 300 with the Kubota motor and really like it. Before I bought it I called a service rep for Kubota out of Texas[I believe it was the main office in the U.S.] and he said they had 2 customers down there that had Kubota engines with very high hours and still going strong. One was running a generator and the other was running an irrigation pump. One had 22,000 hours and the other had 28,000 hours. The one with 22,000 had just routine maintenance done and the one with 28,000 hours just needed a water pump,along with regular maintenance. This, if so is excellent.
I would test it with a "known good" mechanical gauge, because it shouldnt take anywhere near that long, could be a leaky suction line on the engine oil pump, worn engine, whatever the case its not right. I wouldnt run sythetic unless you are in a really cold environment.