I've always heard (and I believe it says it somewhere in the manual) that you should only run 87 oct. in your engines. Unless of coarse, if you are tuned.

Is this true? I have a K&N intake and Flowmasters, no tuned. I would like to run 93 just to see the diff.


I plan on getting the Xcal2 this summer. Then it wouldn't be a problem.

 

It cant hurt. I use 89 most of the time because of the junk gas in cali it makes me feel a little better about it

 

WRONG! Not to be mean, but purely to clarify for your engine's sake..running any octane higher than what your engine is tuned for CAN cause damage over time.

How? Why? Well you should try some google searches about what "octane" really means and what different octanes actually do to effect power. Having a higher octane means it requires a hotter temperature to burn the fuel... which can help when you are trying to avoid running lean, having pinging and knocking problems, and maximize power... HOWEVER if your engine isn't tuned accordingly you actually have a REVERSE effect.

for starters, you will most likely get WORSE gas mileage... maybe not by a lot, but some, and technically less power. OVer time it can lead to buildup from not completely or properly burning either.

So, in short... stick to the 87 octane unless you have a tune for the higher octane unless you want to waste your money and damage the engine.

 

lumadar, I disagree with your premise. Unless you are running some kind of race fuel, pump gas isn't going to damage your engine. An example is the E-85 the green guys want us to switch to. Of course I'm speaking of a vehicle set up for it here, there is notably less power and significantly less gas mileage but the octane rating is equal to standard fuel. Its usually cheaper per gallon but the trade off makes it actually cost more. Ethanol compared to regular grade is the same way and it sometimes has a higher octane rating than regular fuel. Octane is not the only factor in determining the usefull performance of a fuel.

 

Using a higher octane is no good, Lumadar is correct. A higher octane burns slower. You would have to advance the timing in your engine to make up for the slower burn. By not advancing your timing you will not get a complete burn causing problems later on down the road. Get the programer then get the higher octane. There isnt a big difference between 87 and 93 octane but there is a difference. There is a reason Ford put the octane recomendation in the owners manual. Just my 2 cents.

 

Why waste your money? The truck is tune for 87 octane. 93 will burn slower, but will burn a quicker hole in your wallet.

 

Ford engine management WILL adjust for 93 octane and you WILL see performance gains. For all the griping about the weakness of the 5.4 compared to other competitors engines, our Fords are far more advanced.

That being said, there is only so much gain off the stock engine computer. You will not see the same gain as having an aftermarket tuner.

 

Interesting. Is there any evidence to support this? dyno results? If this is true, I still think to extra cost involved does not support the minimal gains that are realized.

 

I am assuming a lot has changed since 2000. When I purchased my 2000 Expedition, the dealer advised me to never use anything but the recommended 87 octane as I could possibly burn up sensors and cause other problems.

 

a search of the site will reveal that this has been discussed many times over the years.

Fords engine management is far, far more advanced than many cars out there and will compensate for the higher octane. But like I said, the improvements are not as significant as an aftermarket tuner so it is a waste of money.


As far as dealers saying to stay away... these are the same dealers that can't correct "the vibe" and like to tell us "that's normal for this vehicle" These are the same dealers that figure out F150 problems 6 months AFTER we figure it out here.

 

In general regardless of engine, run the lowest octane you can get away with without any spark knock. Unless you're running a tuner on a higher octane program or forced induction, roll with 87.

 

agreed. as discussed, higher octane levels do not return sufficient gains to justify the incremental cost

 

Very good point. Besides that it was a female sales person that gave that instruction.

 

Hmmm, wonder if i can put in Pool Chlorine in my tank, the book doesn't say i can't, and its sure to keep all my lines clean
Sorry, couldn't resist.
IMO i would stick with 87 unless you get a tuner.

 

Thanks guys, I guess I figured as much. I'll stick with the 87 atleast until I get it tuned.