I just put in some Amsoil 15-40 Marine oil and Amsoil synthetic filter. Btw, thanks Heath. Could I go a straight 15k on this setup or should I change filter at 7500 , then go another 7500 miles. How are most of you running your oil changes with no bypass filter. Thanks

 

Since this appears to be your first change to synthetic, I think changing the filter at mid stream is a real good idea. IF the engine has any build up, the syn will start to clean it and could shorten the life of the filter. Most of the time I recommend running oil and filter shorter the first but changing the filter serves the same purpose.

 

i was wonderin what would be the best oil for my truck. its a 85 f250 with a 6.9 in it with about 193,xxx miles on it. Any ideas?

 

Are you wanting to change to synthetic? Couple things to consider with your truck due to the higher miles and age.
Does it currrently use or leak oil? If so, to what degree. Chances are it won't get any better and could possibly get worse. I changed over a truck at 269,000 that had small leaks and used some(1qt/3000), but I did it anyway. It actually improved over time (took 15k to get there) and it went down to 1qt/4500miles. It can happen but I think it's rare.
That being said and you still wanted to try it, the HD diesel and marine(15/40) is the way to go.