Oh NO, not another oil discussion...

Excellent info. Thanks for sharing.

7 quarts? Your Duramax sump is 10 quarts.

Your results sound impressive, but... The front & rear differential are spec'ed for synthetic lube, and your owner's manual specifies 7500-mile engine oil drain intervals. An anal dealer could, in a worst case scenario, void coverage if GM felt the vehicle wasn't maintained according to what's required by the engine and powertrain warranty.

Synthetic lube is required by the rear differential because of its higher resistance to breakdown due to heat. Dodge discovered years ago that the rear differentials used in trucks that tow heavy for long distances in high heat routinely failed when running a conventional petroleum gear lube. All of the Dodges and GM's now get synthetic lube as a result. Both Dodge and GM diesel pickups use the AAM1150 rear differential.

Jim

ah yeah 10 Qts, it has been a long while so I couldn't remember the amount and figured 7 sounded about right.

THIS IS THE GEAR OIL I USED

THIS IS THE OIL I USED

After reading this forum from the beginning I have some questions about what type of engine, tranny, and gear oil to use.

I have a 94 6.5 turbo with 152k miles on it. My grandpa bought it new and my brother had it about 4 years before I got a hold of it last summer. I know for a fact the engine oil was changed every 3-4k miles but with Dela 400 and usually a napa, wix, or sometimes a fram :( filter. As for the transmission, I don't know when it has been done or with what oil. The rear end I doubt has ever been touched, and probably still has factory seal on the cover. I currently have a few oil leaks from the turbo, the valve covers, the fittings on the oil cooler lines by the oil pan, and maybe a rear main. During the last oil change i ran the truck about 4 k miles and only added maybe 1 qt, probably not even that much. So, the leaks aren't bad. I usually park the truck and I get about 3 or 4 spots the size of a dime or smaller. Not very big leaks at all.

I have been thinking of running amsoil or another syn. oil but am now worried of my leaks getting worse. Also, the truck has always run dela 400 and this last change has run Lucas 15w-40 heavy duty diesel engine oil. What oil should I run for my engine, tranny, and rear end? Dino or syn? Rotella, dela, or mobil 1 or even another brand? My truck is mostly stock but is out in orchards for farming a lot and is exposed to dirt a lot. Other than that most of the driving is in town, daily driving.

Sorry, for the long question, please bear with me though. I am just trying to catch up on maintenance for a more economical and reliable truck.

I'd snug the bolts up a little on the valve cover gaskets and continue to run the Delo 400 and change it just like before. The 4L80E, I don't think I would switch to synthetic on it, just the dexron that was recommended for it when new, if you can still find it, but convention trans. fluid (Dexron) is what I'd use. The differential, yeah, go with the synthetic, either GM's or Mobil 1 or Amsoil.