im useing the amsoil 15-40 and have heard some ols have a higher shear strength, which oil is the best to be useing in these truck that is synthetic? mobile 1, amsoil, scheaffers, red line?

 

I can't help you with an answer (I'd bet on Schaeffer though), BUT I know where the answer lies:

www.bobistheoilguy.com

Go to the forums, then enter Medium Duty Diesel Engine Oils/Pickup and Vans

 

I used the Amsoil 15W-40 and after 6K miles got a great UOA with it. It's good stuff although you'll have your naysayers....so i say...show me proof.
Schaeffers is probably the best overall value on their diesel rated oils. Great quality products that are fully API certified.
Excellent shear strength. Used by many OTR guy's and heavy equip operators.
Nut

 

The reports I've heard are that the Schaeffer oil is the best for shear resistance. Dual HPOP setups are harder on the shearing of the oil, so I have recently switched to the Schaeffer. I use the 9000 full synthetic. First UOA cam back looking really good.

 

jtharvey - Are you running the 5W-40 Schaeffer 9000 oil year-round? What mileage are you using for your change interval?

Neal

 

Well, I just switched to the Schaeffer's about a month ago, but I have been running a 5-40 full synthetic all year for a couple of years.

On my old oil (Mobil 1) I pushed the change interval to 6000 miles. My UOA from Blackstone said that may have been too many miles. So, with my switch to Schaeffer's, I changed both the bypass and full flow filters at 3000 miles, and topped off the oil. I'll run another UOA at 6000 miles to see what condition it's in, and decide whether or not to change it then based off the results of the UOA.