I have never used synthetic oil in my trucks and would like to know how many miles do you go between oil changes using the synthetic stuff? I am going 6000 miles with Shell Rotella 15w40
BTW I have a 07 5.9 3500 srw if that makes any difference!!

 

The best way to determine extended oil intervals is to do used oil analysis. Good luck.

Boris

 

I go 10,000 when driving empty and when towing, all my tests have come back fine, I could let it go longer but why take a chance, oil is pretty cheap.

 

I was going 5K with regular old Rotella. I am planning on 7500 with this recent change to the Rotella "Synthetic".

(Had 15K on the odometer at last change).

 

Was 5k on Rotella 15w-40
Now 10k on Rotella 5w-40 syn.
The 5w-40 syn will be changing to the CJ formulation as per an email from Shell. So stock up now while you can. I've got enough to last me another 30k.
Then I will probably move on to Amsoil.

 

amsoil 5w30 serie 3000, replace every 12000km

 

I use Rotella 5-40 synthetic and change every 7500 with a Napa 7620XE oil filter.

 

10,000 miles on Amsoil 15-40, using a Fleetguard Stratapore filter.

7,000 miles on a Napa Gold fuel filter.