i have a generac 15,000w rated 22,500 surge with the 30 horse v twin over head valve engine. its a good motor and i will tell you why i think this is so. i have it connected to the house via a master disconnect box so i can power off the mains and power on via generator to run the entire house. i broke it in by running it at roughly 70% load for 5 hours and then changed the oil using delo 15w40. we had a hurricane hit and were without power for about 8 days. the generac ran great the entire time. the only time we stopped it was once a day to check the oil, which after 190 some odd hours of use was still at the full mark. i actually kept refilling it while it ran so as to not interrupt power to our house and our neighbors house. yeah this monster powers 2 houses. the oil was also a nice golden colour. i guess the rings are pretty good in the generac because the oil didnt darken even a little.
if this engine was in a car doing 65mph after 190 some hours it would have gone amlost 12,500 miles. so you can consider this one heck of an extended drain interval. although running at near steady rpm's and only 8 shutdowns, with 1 single cold start, its probably the easiest 12,500 mile oci you can have. i think the manual says to change the oil every 50 hours, but that oil looked so **** clean i just couldnt drain it out that early.
i checked the valve lash after the hurricane and they were within spec, just on the lose side of the spec. i adjusted them and drained the gas, then fogged the engine out so it will be ready to go for next years hurricane season.
its kind of loud running at 3600 rpm's but i put it under a temporary car port out in the yard to keep the rain off it and blocked the sound by parking our vehicles between the generac and the house. the noise isnt too bad then.