use mid grade (87 ) fuel, save's money. but dont forget to fill her up sometimes w/ high grade, octane booster works fine w/ midgrade too.

 

Changing grades of gas is not a good idea. The computer gets used to one kind, then when you put in another kind it has to start learning again.

 

as long as your ignition is in good condition, fuel will burn in the right way.

 

I tried 87 and experienced some knocking so I stick to 91 and above.

 

87 is too low for a 6's. i, guess the engine is made to caliber 91's.

 

I use 91 and still hear a knock. I need to bring my car into the dealer. The thing that sucks is I am the only one here with an Endeavor.

 

not to talk myself up but ive worked 4 a mitsu dealership filling up and drivin cars, the endeavor seems to suck regular, but if u put in super itl last a while, and ive seen that stronger in new eclipses......basicaly suck it up and pay the xtra 15 cents a gallon and ur endeavor will run guuuud

 

these motors have a high compresion ratio so deffinatly super gas only, ive notcied a better improvement in driving when i switched to super from regular.

 

read the gas cap door.
the car is designed for premium, and will ping on anything else (causing a loss of power and milage).

 

I have a 2004 endeavor here in Germany. I use only 93 octane; somtimes midgrade. If you put lower grade in, I noticed it ran like utter crap. Even 89 octane is kinda pushing it. My endevor has 64,000 miles on it and I drive the crud out of it. Autobahn speeds do not seem to hurt it. However, the o2 sensor went out on it. I replaced the wrong one... but once I found the right one, it was really easy... perhaps it was the speed I drive it is why the sensor went out... who knows