Can anyone tell when I can change over to synthetic oil, tranny, rear, engine, on my 07 5.9?

I changed my engine oil over to Rotella synthetic at 3000 miles, then began a regular scheduled change every 5,000. As far as the transmission and rear ends, at intervals of 15,000 should be OK, all depending on how hard you work your truck.

a guy here just converted everything over to Amsoil in his truck a few months ago.....he says he loves it so time will tell.

I love synthetic too in my other vehicles and motorcycle...but have not bit the bullet to do it myself in the Cummins...but may be happening soon as I can do it much cheaper than DD.

You will get lots of opinions on Synthetic for the motor/miles, but the Diffs, Trans, etc all came from the factory with synthetic so you can change them out right now if you wanted too.

I put amsoil im my rear diff and G-56 trans the day it came home from the dealer... The Diff fluid from the factory is horrible at best. I like the AMSOIL ATF so I installed that first thing!

Cummins has always recomended 15k to 20k on the engine.Some don't wait that long, lots do.

changed over to vavoline blue extreme 5w40 at 10000 miles with no problems . just do it and dont look back.

2006 qc 4x4 dark blue all stock

I switched at 3k miles. This last oil change I had to use Dino because I could not find enough of the Mobil 1 TD oil. My truck purrs like a kitten and always has. IMO, some people make too much of a big deal about oils. As long as you keep it changed then you will be fine no matter what kind of oil you use. Most of these people who switch everything to Amsoil and such will probably sell their truck before they reach 100k anyhow. I think it's more about making ourselves feel good then it is about keeping the truck alive, I know it is for me anyway.

I used to work for FedEx and we had a fleet of 5.9 powered trucks. They used the CHEAPEST gas station oil they could find and many of those trucks had 250-300k miles of HARD driving. We never had one have any problems engine related other than lift pumps and broken fuel lines. Just regular oil changes.

Cummins recommended not to change until after the second oil change. I guess to give the rings a chance to seat themselves quicker. That does tell you something about the synthetic's...and wear I THINK..

My truck doesn't even have 10k miles and I've switched all the driveline stuff to Amsoil. I'm gonna wait til 20K miles or more to switch the engine over to syns so everything can seat in. I'm running Delo 400 15W40 in that for now and considering amsoil series 3000 5W30 HDD for later.

My truck doesn't even have 10k miles and I've switched all the driveline stuff to Amsoil. I'm gonna wait til 20K miles or more to switch the engine over to syns so everything can seat in. I'm running Delo 400 15W40 in that for now and considering amsoil series 3000 5W30 HDD for later.

You may end up with better wear numbers with Delo over Amsoil.

That's what I've read from more than a few people here and elsewhere. I'll have to see what oil analysis says but so far on the drivetrain stuff I am happy my trans certainly shifts noticeably a lot smoother.

That's what I've read from more than a few people here and elsewhere. I'll have to see what oil analysis says but so far on the drivetrain stuff I am happy my trans certainly shifts noticeably a lot smoother.

Yeah their drivetrain lubricants are awesome, for sure. I was quite pleased with their performance.