So I just finished putting 5 quarts of walmart 5w-30 synthetic and a cheaper Fram filter in my 91 chevy caprice 5.0L/305 Throttle Body with 152k miles on it in 10 degree weather and -10 windchill thinking "this sucks"... yet what came out after 3200 heavily highway miles on the last dino oil I intend the car to see was pretty dirty looking (I used to be on a strict 2000-2500mi change with dino oil on every car but i'm getting a bit lax because of cold and aggravated physical disabilities the last year) and so I was feeling a little doubtful about things I hear about people going 7500-10k miles and all that. I realize it might well depend on the engine and circumstances and other things so I figured i'd ask the people that would know best. :-P How often should I be changing synthetic on a small block v8? Although this an old and not too valuable car I still like it and hope to drive it for a number of years yet through college and grad school so pinching every possible penny is not the goal, just general frugality. If I have my way i'll have it another 100k miles yet. One reason I went to synthetic and in case it affects things is the wear of starting in the cold (minnesota boy) and that when I drive to school 4x/week it's very close and the car barely has much chance to getwarm. But then once per week I have to drive 250 miles one way for ongoing medical treatment and do 30-45 miles a day of bigcity driving the next few days, so it's a mix.