I have a '92 F150 302 5 speed that I bought used with about 125K miles. I have had it about a year and immediately changed the oil to 10W30 Mobil 1 (synthetic), based on experience with synthetic oil in other vehicles---for example: 1985 Firebird (5 liter) bought new---234,000 miles, all on synthetic, (with no engine related repairs)on it when I totaled it; 1988 Taurus V6 bought with 48K miles---changed to synthetic oil---had 219,000 on it when totaled (no engine related repairs); 1990 Cadillac Sedan DeVille---bought at 85,000 miles, changed to synthetic oil--had 190,000 when sold wh\ith no engine related repairs. Do you think I would want to use a petroleum based oil just because it is cheaper? With synthetic oil, change your oil about every 20,000 miles (change filter as recommended by mfg)---thats 3 to 5 times what petroleum based oils should be changed. Oh, my '96 Cadillac SDV is on synthetic oil---and has about 94,000 miles on it. Try synthetic oil---you'll save money in the long run

 

 

Only thing I've heard to the contrary is switching to synthetic after a lot miles is that because it tends to develop leaks (more lubricating).
I'm gonna go to syn after 500-1000 miles.

 

You should break in a new car with regular oil recommended by the manufacturer. I would put on at least 5000 mile to set the rings and lifters then switch to synthetic. Thats from a gentleman who use to work for Mobil. The wear on a engine on Mobil 1 in 100k of testing is + or - 1-5% Thats less then regular oil with 10K of wear and tear? Think about it?
Paul

 

I agree with your comments completely.
Although I use Valvoline syn. in mine, I think that
switching to syn is all that matters