5-40 diesel oil

mathematically it will cause a .009 or so loss in mpg, but a thicker oil may help in hotter temps like here in florida

Any difference in protection? I run a lot of miles and sometimes they are very hard miles with my job a small loss of fuel mileage is no big deal to me

Any difference in protection? I run a lot of miles and sometimes they are very hard miles with my job a small loss of fuel mileage is no big deal to me

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in hot climate it should provide more protection since at higher temps it should stay a little more thick thus hold its properties better. now if you live in Alaska where it gets extremely cold a thinner oil would be better since its more fluid during cold start up

5-xx vs 5-xy is the same in cold weather.

I use the 5w40 amsoil mid saps. I like the 40 for the turbo because of high temps.

Ive run both, I'm sticking with the 30W now after oil analysis didn't show any difference with the 40W. It won't hurt at all to run though and like others said would probably be slightly beneficial in high temp situations. The 30W oils that meet the low-saps light duty diesel specs are already basically a 38W as it is. They're a whisker away from being considered a 40W viscosity wise.

I've strictly used 5W30 in mine for all 148K miles. I drive it hard too, but I always let the turbo cool down for a few seconds before shutting the car off.