I like most on BITOG have a standard we go by with our OCI's and that's usually by mileage, In the past on my 5.3 Silverado ive always done 1 year or 5,000 miles with whater Syn was on sale. I know that's not a lot of miles for syn however that's just what ive stuck to as this truck does see some heavy duty pulling trailers from time to time. That said Ive used the truck little this year and only have about 2,000 miles since my last OCI. Im getting the itch to drop the syn and just go with a conventional and stick to my once a year change. I absolutely hate the idea of dropping that syn out of the sump with only 2,000 on it. The truck never makes less that 20 to 30 minutes runs down the road when I do drive it so the oil does have a chance to get warm. so what im wanting are opinions on time. whats the longest youd feel comfortable leaving syn oil in a sump on a non daily driver.