I just bought 5L's of 0W30 GC gold on sale at the local Walmart to run on my next oil change in my 1987 Chevy Caprice winter beater. It's a carb'd 307 Olds roller cam V8 with about 160k miles on it. I do my own oil changes outside in the cold and it will regularly be between -10 and -20C here this winter. Since I hate working in the cold I'm hoping to extend the oil changes as long as I can I'm just wondering how long I can safely go without getting it sampled. The car is well tuned and the choke is tuned as well as possible but there will still likely be more fuel dilution than there would be with fuel injection. I drive 35 minutes one way to work, mostly at around 50mph country roads about 55 mile round trip. I only let the car warm up for about half a minute before driving off. The car uses about a qt of oil in 2k miles. How long do you think I should let it go?