Hello everyone, I have a question regarding octane. Manual recommends I use 87 octane in my 2006 F150 FX4 5.4L. I got 14.12 mpg on my first tank of gas and was wondering if I will get better gas mileage, better performance and a cleaner burn using a higher octane, or will a higher octane cause problems since the engine has been set up for 87 . Also, I should add that I am not running programmer yet, truck is totally stock.

 

Running the LOWEST octane your vehicle will run on without pinging is best for performance.


However, with todays electronics, it's sometimes difficult to make a motor ping since timing will be pulled to prevent the pinging.

In answer to your question, you will not gain anything by using higher octane than you're rated for using the stock tune.

 

DOHCmarauder....thanks for the reply

 

Octane dependancy is another problem, if you run super for a while your truck will start to ping on the lower octane gas.

 

I'd like to hear the reasoning behind that theory...

 

You will gain nothing over a higher octane other than a lighter wallet. The sensors will tell it's higher octane and compensate. So you shouldn't notice anything.

The only reason I can think of for using the higher octane is if you have a programmer installed. Or if you live in the cold climates. Up here in ND, the 89 octane is 10% ethanol. That'll help stop your fuel lines from freezing up in the winter. Nothing for performance. Just for cold starts in the cold.

 

the higher the octane the hotter the burn

 

Acutally, i have heard that higher octane burns cooler. in fact i run it in my sled when the temps rise and the sled runs cooler.

 

Don't worry, your fuel milage will get better with each tank of fuel. It MAY take up to 7-10,000 miles to get the engine broke in to where it gets its best milage. Good luck with the new truck!!

 

Higher octane fuel contains more POTENTIAL energy but requires the higher heat generated by higher compression ratio engines to properly condition the fuel to RELEASE that higher potential energy.

 

Octane has nothing to do with energy. That's just what the gas company's want you to believe. All octane has to do with is at what point does it explode while under compression.

Low octane will explode sooner than high octane. Once the explosion occurrs, same energy.

Higher compression engines develop more HP not because of the gasoline octane. The develop it because higher compression itself makes the HP. Not the gas.

 

I tried to find a thread on it from the V-10 forum, but the search function seems to be down at the moment. From what I remember it had something to do with carbon build up in the heads. I'll try and find the post on it later..

 

92merc

that is what i said, yes it has to do with energy, without it, you go nowhere

 

None of the modular motors seem to gain anything from running anything greater than regular....


Unless you are running a blower of course

 

A couple of really close answers. Octane rating is about when a fuel will SELF ignite or will explode due to pressure/heat (which can happen before & after spark is introduced). THAT'S IT, it tells you nothing else in and of itself.

You can't use octane rating by itself to determine energy content (one brand of fuel could have more energy in its higher octane fuel, another could have less compared to its lower octane), potential mileage or the speed of the burn (many higher octane fuels burn faster though, by design, even talking pump gas). There are different formulas and types of chemicals used to increase octane levels and different individual engines (even the same engine under diff. circumstances/state of tune) will react differently to them. It even gets to the point of how accurate your MAF, 02, and other sensors are.

Basically, you need to do your own experiments, it's virtually impossibe to compare experiments with others. WAY to many variables



Except for his answer to this question: "Is it better to raise fuel octane or lower the octane requirement of the engine?" (I only disagree because the answer is very much oversimplified, especially refering to pump gas) this is a very informative article and pretty well spot on.

http://www.eric-gorr.com/techarticles/Fuel_Basics.htm

Keep in mind if you really want to understand this subject of fuel you're going to need more than a few articles and replies, you need a few books worth of info.

My '99 4.6 gets consistently and noticeably better mileage and power on a certain brand's higher octane. I don't mention the name as it could be a different formulation in your area(s), and again, your vehicle may not show any higher anyway, even using the same exact fuel.

All that being said, your mileage increase, if any, will at best barely break even the increased price of the higher octane. It may even go down. Any power increase, if it happened, would be your call as to "worth it" or not. As for cleaner burning, it's so close as to be almost a non-issue with todays fuels and vehicles from what I've gathered.