Kinda considering a tuner to help shifting points and get more power but I am at almost 6000 FT and hi octane (from what I'm told ) does not do as well "up" here. The basic grades of octane here around the Denver area are 85, 87, and sometimes 91. The 87 is 10 cents more a gallon than the 85 and the 91 when you can find it is 20 cents more. Right now I am running 85 octane but have run 87 and ran 1/2 a tank with 91 once and haven't noticed any difference in mileage or no noticeable power gains. Would a tuner actually help any mileage? I know that more power would eventually cut into the mileage at some point and would consider the trade off at times. Its just that I really don't want to spend the extra 20 cents a gallon if I don't have to. With a 37 gallon tank gets a little pricy to fill up.

 

Hi mkinttrim,

Being at high altitude does not present any problems for tuning your vehicle for any level of octane you have available. It is *not* true that high octane does not work well at high altitudes - that is a myth. What *is* true is that high octane simply isn't appropriate for use on your stock factory tune, at *any* altitude, because the engine isn't tuned for it, so it cannot take advantage of it.

On the stock factory tuning, you should use not more than 87 octane (unless it detonates), as it's not tuned for anything more. So on the stock factory tune, there is no benefit to running any higher octane - in fact, you can easily find in some cases that you make *less* power and get worse mpg by running premium gas on the stock factory tune (again, at *any* altitude), and that is even mentioned in some of their owner's manuals. This is because as you go up in octane, it takes longer to get the air/fuel mixture lit, so it requires more time both in terms of real time and degrees of crankshaft rotation - thus the engine needs to be specifically *tuned* for the level of octane it's going to be run on in order for it to make proper power, have correct driveability, and get the best mpg.

Up at very high altitudes, octane requirements are reduced a little bit, now that is true, to a certain extent. So at high altitude in some areas, 85 octane is generally considered "regular," where 87 octane is considered "regular" everywhere else - 85 octane is very rare overall, but that is found in some locales at high elevation.

What will get you the best results along with the most flexibility is to have us do our custom tuning on your truck. We provide a set of 3 different custom tunes, set up the way you want them - for example, we can set it up for each octane level if you like.

Now of course the largest power & performance gains are going to come from premium gas tuning, and you will find that as long as you keep your foot out of the firewall so to speak, you will generally see an improvement in fuel mileage as well, so that you really don't pay much, if any more for fuel running it on premium with our premium gas tuning, and can enjoy the increased performance and driveability, etc.

Just FYI - mixing a half a tank of premium in with a half tank of 87 isn't going to do anything for you on your stock tune, nor would straight 91 or even 93 octane - also remember that mixing octane is linear - I.E., 5 gallons of 85 and 5 gallons of 90 get you 10 gallons of 87.5 octane.

We can provide power gains and better driveability as well as far better shifting, etc. on any level of octane you have available, so you don't have to run premium to get improvements - it's just that is where the *highest* power gains are had, of course.

I hope this brief info helps you, & please feel free to give us a call at our number listed below to go over all the various details - we also provide registered members of F-150 Online like yourself with a special discount on our tuning products.

Thanks for your post, & best of luck with your truck!

 

Thanks for the info!

 

Yeah. The reason that we have 85, 87, and 91 octane is the amount of air that gets compressed with the fuel mixture is less at higher alt. If you were to run 85 octane at say sea level, you would probably have a detonation problem (compression knock). The more air you can get into the fuel mixture (oxygen), the more chance you have of knocking. In CO, we have less air pressure = less oxygen = less knocking. The more heptane in the fuel also lends itself to knocking problems. This is a good article on fuels and knocking: http://www.superchargersonline.com/content.asp?ID=105

 

That's a decent "layman's" article covering some basics that those who do not feel familiar with this should indeed read - I don't agree with all of it, but it does cover some important basics, absolutely.

It should be noted that the type of special single cylinder variable compression ratio engine that is actually used to determine octane ratings is *not* any "normal" kind of engine you would find in any motor vehicle - instead, it is just what I said, a special single-cylinder variable compression ratio octane rating engine. The continue to increase compression ratio until pre-ignition occurs, and that is how they determine the octane rating, the octane point at which pre-ignition occurs.

They also started that you have to use premium fuel to use any kind of programmer, and that is only true in the most basic & elementary, limited type of devices, not in any of today's modern devices - so I'm guessing that article was actually written years ago, and we've seen in before for some time. Today's tuning devices offer multiple programs, including tuning for "regular" gas of 87 octane that still allows better power & performance, driveability, better shifting in the automatics, and all the normal benefits of good sharp tuning over the stock factory tuning.

Just FYI....