This topic on oil has probably been discussed a thousand times on here. As you will find almost everyone has their preference. I use Shell Rotella 15W-40. I have talked to trucking companies that used Shell Rotella with great sucess. It appears that some of the top oils are Shell Rotella, Delo 400, Mobile One Delvac, Schaffers, Amsoil, Redline and so on. Some use Dino oil and others use synthetic. Probably any of those oils would provide great service. Would one certain oil allow the engine to go alot longer, mileage wise without any problems? I don't think it has been proven. It appears that the key is regular oil changes when needed. Good luck on your decision.