Is one any less able to make a 25,000 1 year OCI's. Both advertise that they can do this but is one less able to do it for lets say a 4.0 Jeep that likes a 40 wt. oil.
Just wondering and thinking things through before I make a new order.
If comparing the 10w30 and the 10w40. The 10w40 would be less apt to make it as it contains more Viscosity Index Improvers. Whereas the 10w30 contains none.
Now the 5w30 vs. 10w40?? My vote would be to the 5w30. Though as your jeep like a 40wt I'd go for the 10w40 as it's your choice. I would go conservative on the first oil change, say 6 months or 10,000 miles. Then step it out depending on your driving style.
Hope this helps
The Amsoil 10w-40 will tend to shear a bit during the first 10,000 miles and then start to thicken back up after that point. The Amsoil 10w-30 may actually show a bit more relative thickening after 20k-25k miles, since it's more shear stable. The 10w-40 does use an SL/CI-4 additive chemistry, so I think it will keep the engine a tad cleaner ....
Wear protection will be very similar with both oils, but you may see a bit less bearing wear with the 10w-40. However, the friction modified 10w-30 will provide a fuel savings of perhaps 2% over the entire drain interval and will reduce your peak oil temps by 5F-10F.
I started out running the 10w-40 in my Audi TT roadster, and now have about 8000 miles on the 10w-30. Oil consumption has been the same with both oils, but subjective engine performance and turbo response is better with the 10w-30. I haven't tested the 10w-30 yet, but wear was very low with the 10w-40 I tested back in the spring. ....
The Jeep engines generate lots of iron wear,which I expect is corrosive wear; coming from the valvetrain. So this may be an application where a 5w-30 or 5w-40/10w-40, CI-4 rated, synthetic diesel oil is preferred if you want to get 300,000 out of the motor.