I have started to use super or premium unleaded. Truck seems to like it my gas mileage has gotten better too, I was told it's better for the engine. What do you use?

 

Just regular here. That's what the salesman told me to use, if fact he said DON'T use premium, and only middle grade if regular isn't available. So far no problems. Fuel mileage I don't even look at anymore. If I wanted something good on fuel, I would not have bought a truck, LOL!

 

I've always run the mid grade 89 octane in my Hemis. As you said they seem to like it better and the MPGs are slightly better.

 

I've run every octane in two hemi trucks and have seen no difference in performance or mileage, so I usually run 87 now

 

I typically run 87. I ran the 91 SuperChips tune in the truck for about a year, and kept 91 in there. I could tell a little difference in power, but none really in mileage. Of course I think the SuperChips tune is geared more for performance than conservation really.

 

I run 87, notice no difference when running 89. Only time I run 89 is when I tow.

 

Unless you are running a tune that requires premium you are absolutely wasting your money. Our trucks are designed to run on 87 and 89 octane and don't need premium fuel at all, and it isn't going to make your truck run better or get better mileage. If your mileage has gotten better it's because you probably have changed your driving habits so you can make a claim, of better mileage on premium' to justify the waste of money from using it. As far as it being better for the engine, there is no advantage to using premium fuel in a motor that wasn't designed for it. I have run hemis for nine years now and they don't need or want premium fuel as long as they are running a stock tune

 

87 octane.

However, here in Canada, I don't think they add ethanol. When I cross the border and fill up with the same octane, mileage seems to be a little worse; maybe 1mpg less.

 

89 in mine. Old habit from my 06' Hemi. Hesitant to run 87 in this one.

 

Pretty sure that in Canada most provinces require for fuel to have an average of 5% ethanol. That means 10% in 87 Octane, 5% in 89 and 0% in premium. However, some gas stations have ethanol in all grades. Most pumps I see nowadays have fine print that says "may contain up to 10% ethanol". I live in Newfoundland and even though our province does not require this, most of our fuel comes from Irving in NB and ever since they started blending ethanol in their fuel my mileage has gone downhill. I use 89 octane and have always found that I get about 30 to 50 more kms per tank with 89 than 87. Sometimes I cheap out and get regular, but then I notice the drop in mileage and I switch back to 89.