The manual definitly says to run 89. I am reading it right now in the owners manual...at least for the '04


And the 07 said the same...you were running the wrong gas.

 

Sobo, how did the truck run with 87?

 

I never noticed anything wrong with the truck with 87 in it. It ran just fine, even under heavy acceleration or towing.

 

Feel free to buy up. It's always appreciated. If y'all ever need any t-shirts or embroidered polos, I can help y'all out. I did Crossfire polos for the guys over at the Crossfire forum.

 

I was being a cheap bastard and using 89 in my truck, and the truck just felt sluggish. Switched back to 93 and got my silky smooth power back

 

I copied this from the owners manuel.

"The 5.7L engine is designed to meet all emissions regulations and provide satisfactory
fuel economy and performance when using high quality unleaded gasoline having
an octane range of 87 to 89. The manufacturer recommends the use of 89 octane
for optimum performance."

You can user 87 or 89, Optimun Performance what ever that means.. Mine runds fine on 87.

 

Mine didn't like 87. Terrible (even more) mileage. Poor performance. He gets 89 regularly, with an occasional 1/2 tank of 93. I have a road trip coming in a few months. I may run down on 93 and back on 89, just to compare the mileage. If the mileage offsets the fuel cost, I may run 93 more often.

 

From everything I've read, your driving habits, traffic, terrain, etc. will affect your mpg much more than the fuel.