My tunes.
87 performance
93 tow
93 performance

I'm currently running the 87 performance tune. I have a little less than 1/8 of a tank. I need to tow something long distance. I want to go ahead and fill up with 93 octane and install the 93 tow tune. I don't have time to burn off the 87 octane that is in the tank now, nor do I have time to return to stock and tow the equipment and stop in BFE and put cheap 93 octane in the tank.

Will it mess things up if I go ahead and fill-up with 93 octane with less than 1/8 of 87 octane fuel in the tank now, and install the 93 tow tune?

 

Can't believe you would have a problem.

 

cottonhead;I would set back to stock and run the 87 out and after you refill with 93 then set the 93 tow.I know mine takes only 3-5 minutes to retune.JMHO.When I set mine from 87 tow to 93 tow after the the fillup I got spark knock till the 93 flushed out the 87 in the injectors.Of course I floored it out of the gas station,but I did get knock for a couple of seconds.

 

There won’t be any problem mixing 93-octane with 1/8 of a tankful of 87. That approximately 3 ¾ gals of 87 to be mixed with 26 ¼ gals of 93; no problem

 

Just did it today....fuel light for a tank of 87 octane went on last night as I pulled into driveway. I woke up this morning and my xcal2 was waiting at the door. I went and filled with 93 this morning, programmed with 93 performance and WOW! Love it, not worried at all about a few gallons of 87 still in the tank.

 

Can you get a chirp at take-off?

 

You know what I haven't tried...at least not yet. I am impressed though, I have real seat of the pants performance that I can really notice. I've always thought my truck ran pretty good anyway. I love the way it runs now...i'm going out later i'll mash the gas and let you know.

 

Dug this up on a search this might help better!
Superchips_Distributor
Senior Member &
Supporting Vendor Join Date: Mar 1998
Location: Virginia
Vehicle: 2001 Ford F-150 SVT
Posts: 12,300

Last - when changing octane levels from a regular gas tune to a premium gas tune, this is easy to do - just run the 87 octane fuel down low, we recommend running the tank of regular (87) down until the low fuel warning light comes on, or close to it. Then fill it up with premium, and you cna immediately load your premium gas tuning. You cannot take say, 1/2 or 1/4 tank of low-octane fuel, top it off with premium and load up tuning designed for premium fuel, as you would dilute the incoming premium fuel too much. Don't worry, this is something you'll get used to very quickly.

Now going the *opposite* way, say if you are switching from premium back to 87 octane tuning, then you can run it down to about 1/4 tank or so and fill it up with 87 octane, and immediately install your 87 octane tuning - that won't be a problem.

These 2004 & up F-150's generally have a 30 gallon gas tank, so there's still a good deal of fuel on board when the low fuel warning light comes on, usually on the order of about 3.5-5 gallons, just to give you a rough idea.

If you'd like to go over any of this in more detail, please feel free to give us a call at our number listed below & we'll be happy to help.
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Last edited by Superchips_Distributor : 11-28-2005 at 11:47 AM.

 

Thanks for that quote.

And no, we DO NOT advise just adding premium gas to 1/8th tank of 87. See,
these 2004 & newer trucks have a MINIMUM of a 30 gallon tank, and a rather non-linear gas gauge.

At 1/8th indicated tank, you can easily still have as much as 7-9 gallons of 87 octane left in there - add 23 gallons of 93 to 7 gallons of 87 and you have 30 gallons of 91.6 octane. Add 21 gallons of 93 to 9 gallons of 87 and you have 30 gallons of 91.2 octane (these are approximate numbers, as octane mixing in this manner is relatively linear). Either way, that's not really enough to run a tune that is designed for 93 octane, IMHO - the knock sensor system may or may not be able to catch that under all situations.

This is why we say that when you are changing to a high octane tune, run the low octane down until the low fuel light comes on - and if you are at 1/8th tank, it is NOT going to take much to run it down properly - heck, hook up your load and tow it on the STOCK program, and that will run that 87 down quicker - then just fill up with premium and switch tunes *then*.

Also - and I almost hate to mention this - In an *emergency*, you can always drop by AutoZone, etc., and pick up a couple bottles of the blue NOS octane booster - now as everyone here knows, I am NOT a fan of using octane boosters, but the NOS brand leaves behind the fewest deposits on spark plugged & O2 sensors if you need to take care of such a situation.

I hope this info helps!