The manual specifies 87 for the 4.6 and 5.4. I have been using this with no pinging at all. However, last fill-up I used 89, just for the heck of it (gas prices are dropping here). Now it seems I have a bit more power from the 4.6. Is it just psychological or something? what octane do you use? do you notice power changes? do you think the ECU is advancing the spark a bit as it listens for ping?

 

I run 93, but I have a Superchips Program running. Before that, I ran 87.

 

87 currently, but planning on a custom program and wil need to adjust up then.

 

In the past 110,000 miles in every kind of tough conditions with and without a heavy load, in heat up to 120 degrees, I've used 87 octane in my '97 5.4L with no knocks of lack of performance. Never could tell the difference if using higher octanes when 87 wasn't available. I do notice immediately if I use a lower octane part ethanol fuel like found in big cities or out West, because the engine check light comes on, and it will ping on acceleration or heavy pulling. A curse on whoever thought of using ethanol and oxygenators in gas with a low octane rating.

 

radar_ridr:

I use 87 octane in my 5.4 and the same in my 4.6 without a problem....ever. A well maintained engine shouldn't need the extra juice, unless you are approaching the 200 thousand mile club!

As for feeling some extra power when using 89 or 92 octane i would have to agree with you on that. At least thats how my 81 F150 with a 4.9L (209,000 miles) responds. Excessive carbon build-up causing the compression ratio to be increased.

-hooD

 

I live in MT and we have 85.5 I've ran it a couple of times, but don't like it. I now run the 88 octane in it. When I go some place normal, I'll fill it up with 87.

Hudge1

 

I have a 99 f150 5.4L v8 and have always used 91 octane in my truck except when I was low on cash then I would put the 87 octane in and noticed that I didn't get quite as good of acceloration. Now I always run 91 because I put a chip in my truck, I would put 93 octane in which is what the chip recommends but I have not found any place that sells 93, the highest I'v found is 91. If anyone knows where to get 93 let me know.

 

ssKable,

I moved to MT in Dec. 2001. Once I crossed the border from SD to WY, the octane dropped. I've only seen one place that sales anything in MT above 91, and that was in Missoula. Due to the higher elevation that is why the octane ratings are lower where you live.

Hudge1