Let me begin by saying that I was the first to say that “you don't need to use higher octane gas on cars/trucks that were designed to run on 87 octane”. I always said it was a waste of money, and only your mind was telling you it worked better to run higher octane gas.

That was until 89 octane was accidentally put into my 04' Expedition EB. My wife filled the tank in my Expy, and I started to notice how well my truck seemed to run. I also noticed that I gained 1.5 mpg under mixed driving. After finding the receipt on the cupholder, it shown that she pumped 89 octane!

Before I noticed these improvements (more peppy, better mileage), I had no idea she used anything other than regular gas, so the placebo effect doesn't explain my better seat of the pants and mileage improvements.

Does anyone else here use 89 or higher octane on their 4.6L V8 trucks/SUVs? Have you experienced the same thing as me?

 

I ran 89 in the 98' 4.6 I had because of pinging if I didn't. I only run 89 in my 03' 5.4 now and don't want to know what 87 will do.

 

If you got better milage out of that tank, it was a coincidence. Your engine is designed to run on 87 octane and unless you get getting a lot of detonation ("pinging"), there is aboslutely no benefit to using anything rated higher than 87.
Ive had a lot of people tell me that with 93 octane fuel you will get more power, better gas milage, that it will burn cleaner and is of better quality; but its not true.
Unless your engine has been modified to have higher compression, you are wasting your money by running anything higher than 87.

 

Octane, what you are saying is the party line, so to speak. If your truck runs better and gets better mileage on higher octane fuel, run it if you can justify the extra expense. It's very possible that it will run better and get better mileage because if it has a knock sensor it will allow more timing advance. Some vehicles respond well, others don't, and you can't make a blanket statement.

A friend has a 99 Sable with the 3.0 Vulcan - he gets 3 mpg better on 89 than 87. I had a 87 Taurus and 87 Sable, same engine, and in both of mine octane made no difference at all. I also had a 89 Beretta with a 2.8 and I got 3 mpg better on 93 than 87.

My truck gets slightly better mileage on high octane and runs slightly better, but not enough to justify the expense.

 

I run 89 in my 5.4

 

I run 93 in my 05 150 5.4 get 2 miles to a gallon better on the highway

 

... and I guarantee you are actually losing power above 4,000rpm because of flame propagation differences. The KS system cannot adjust advance enough to account for the much higher octane fuel to be burned efficiently. Only retuning can do that properly.

You are wasting your money; this is well-documented here - I suggest you do some research. Hint - the Chips forum is where the bulk of this advice resides.

 

I'll do another tank on 89 to see if it changes. Interesting to say the least. I do know our Honda Oddessey is designed to run on 87, but it says in the manual that it will make increased performance on 89, though it was tuned to have that ability, my Expy was not.

 

I don't care what anyone says about efficiency, etc. etc. - it's the butt dyno and the gas mileage calculations that make a difference, and what works for one person doesn't work for another. Brand of fuel can make just as big a difference too. Find what works best for you, and use it, doesn't matter what it is.

On my truck, when I was in the Chicago area, BP 87 octane E10 worked best, down here in MO it's Murphy 87 at Walmart - believe it or not. BP is hard to find here. I've tried 89, 91, and 93, and there's not enough difference to make it worth it.

 

Well, I'd have to wager that several hundred dyno runs assessing fuel octane quality and octane ratings on the F150 platform would probably provide some purdy good data points for this argument.

Bottom line - the late-model F150 PCM, while having the ability to advance a limited amount, for one or two points, still cannot accommodate the slow burn that 93 exhibits. Hence, power loss at higher rpm's where there is the least amount of time to fire & propagate effectively. That is a fact. Period.

Other vehicles may indeed have a wider range, the F150 does not.

If you are detonating on quality 87 on a stock truck, you likely have some sort of issue- most likely carbon buildup causing an artificial compression increase. Adding octane is a bandaid, not a solution.

 

The limited amount of advance you speak of, you think it could have a positive effect on 89 octane?

 

Yes - one or two points would be within the limited advance range.... my diatribe was directed at those putting in 93 lol

 

Cool, I'm telling you, I always told people to only use the recommended gas, nothing higher unless you retuned.

But even before I found out my wife put 89 in my Expy, I already noticed the better mpg and pep when I thought she filled it with regular. I'll continue with 89 for now, even though it's $3.25 already here in San Diego.

 

The best gas mileage I ever got in my truck was on 85 octane mountain gas in Colorado - go figure. NO pings either.

 

I use premium all the time, for the simple reason of gas mileage, which it makes a very noticeable difference.