We used synthetic in our V10. We changed on mileage only (technically every 15000 km). We had no genny but used a zero gauge cable to the house batts so we idled sometimes an hour a day. We sold it last year with just around 190,000 km on it. Never used oil.
We do the same thing in our Cummins ISC on our big motorhome. Lots of miles and no problems.
Our cars are both electric so once a year we fill up the washer fluid and we are done for another year. :) Still on the first jug of washer fluid which I think I got free with a fill up a few years back. .)
