Ok I used to work in a big rig shop. I started out in the lube pit and most of the owner operators who were real picky about their trucks and had the big Petes with Cat motors ALL ran Rotella 15-40 with a gallon of Lucas. Equivalant of my truck being Rotella with a quart of Lucas mixed in. Now I'm readin in a couple places that Rotella AND Lucas are junk? I don't know NEARLY enough to make an educated decision cuz I don't know about all the technicalities that some of you here seem to know. So I appreciate the vendors will want me to use what they sale and I'm open to hearin what they have to say, but I really want to hear from the unaffiliated third part guys to see what's worked for you.