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  #1  
Old 09-27-2010
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switched gas now bad mpgs

i went from 87 octane to 93 octane amd now im gtn about 1.5 to 2 mpgs worse anybody knw why?
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Old 09-27-2010
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Originally Posted by rpwillix View Post
i went from 87 octane to 93 octane amd now im gtn about 1.5 to 2 mpgs worse anybody knw why?
because you effectively lost ignition timing by making this switch
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Old 09-27-2010
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how did i lose ignition timing
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Old 09-27-2010
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Did you switch from regular fuel to oxygenated?
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Old 09-27-2010
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i dont think so...idk what that is...all i did is hit 93 instead of 87 at the pump
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Old 09-28-2010
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Originally Posted by rpwillix View Post
how did i lose ignition timing
because the peak combustion force is happening later than it would if it were 87 octane
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Old 09-28-2010
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why would it happen later and not at the same time as before?...sorry bout the double i didnt see that you had answered on this one my phone is slow and i dont have access to a computer
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Old 09-28-2010
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why would it happen later and not at the same time as before?...sorry bout the double i didnt see that you had answered on this one my phone is slow and i dont have access to a computer
your not using the same octane fuel.

please do some research on octane and how this changes combustion rate
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Old 09-28-2010
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yea the higher the octane the harder it is to get the fuel to burn...thats why turbo/supercharged cars require you to run the hi test
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Old 09-28-2010
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ok thanx
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Old 09-28-2010
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ok so at quick glance what i have found is that A: higher octane fuels help engines from knocking in the event that are and B: really only do you good in high performance engines with a high compression ratio so therefor do no good in a stock engine...however i upgraded my coil to a msd coil which according to msd's tech gave a hotter spark which in my mind would burn the fuel quicker but apprently that has no real effect on the octane used?....furthur more i found a chip for my truck from JET and i was talking with there reps and they recommended using higher octane and its suppose to raise HP/TQ, mpgs and various other things so if im having this response to the higher octane fuel now how am i going to raise my mpgs with the chip? does it automaticly change the engine timing and so forth to effectivly produce more mpgs?
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Old 09-28-2010
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cars have learning computers, like the terminator, so it has already developed a plan of what is optimum for the fuel used under given certain conditions.

take the negative off your battery and hit your breaks till the lights die, usually 5 seconds or so, then reconnect the battery. this will reset your ecu and it will develop a new way to operate with the 93
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Old 09-28-2010
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Originally Posted by ES894x4 View Post
take the negative off your battery and hit your breaks till the lights die, usually 5 seconds or so, then reconnect the battery. this will reset your ecu and it will develop a new way to operate with the 93
OMG sooo wrong... if this were true I would be out of a job!

Your timing map will only be reduced by problems feeding back into the knock control logic (If his truck even has that). Computer will not randomly advance timing looking for knock and say "ok - that's enough".

LOL - too funny. Good try though.
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Old 09-28-2010
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simple answer that I would understand: your engine is not tuned for the higher octane fuel. Meaning your programming is not sync'd with the new fuel.
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Old 09-28-2010
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Originally Posted by Fx4wannabe01 View Post
simple answer that I would understand: your engine is not tuned for the higher octane fuel. Meaning your programming is not sync'd with the new fuel.
thanx for the idiot proof answer i was lookin for ill just wait till i get it chipped and run higher octane like they suggest
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Old 09-28-2010
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Yeah no probs. lol...I don't know anything about what you have but the common tuner ALOT of guys run is an SCT Xcal2 or Xcal3 from Rogue Performance. You get 3 different tunes of pretty much your choice and they're written for the fuel you'll be running. For example, my tuner has 87 econ, 92 torque, 92 power tunes.


Go make yourself a signature telling us a little about your truck. You can do this by clicking "User CP" on the top left then clicking "edit signature". If your truck is too old, you're SOL on a tuner.
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Old 09-30-2010
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its a 93 xcab 3.0 ranger auto but JET performance makes a chip for it and thats what im wanting to get
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Old 09-30-2010
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Negative folks. Timing will NOT be affected by higher octane fuel - and if it does it will only be in a positive way. The only way it will affect timing is if pre ignition is occuring - in which case higher octane fuel will help you.

Simple scenario: If you light a match on 93 octane fuel and on 87 - "combustion" will occur at the same exact time.
It does not matter if this scenario occurs inside of a "combustion chamber" or not.
many do believe that 93 is more difficult to burn. That is one of the more asinine car myths I have heard in a long time. It is simply not grounded by science - nor is it true.

My bet: You had a bad tank of gas, you may of pumped at diffrent times of the day, diffrent gas station (some gas station have more ethanol, etc.), seasonal change, the possibilities are wide and broad.

If you would like to conduct a proper investigation; I would suggest you:

full tank of 87 octane - monitor MPG.

Full tank of 93 octane - monitor MPG

Full tank of 89 octane - monitor MPG

**All at the same gas station brand & location**
** All pumped at the same time (preferably after 8 PM when weather is more steady)
-ensure that other variables are constant throughout the expirament-

This will give you the necessary variables and equations to come to an educated conclusion.


Report your findings to us in about 3 weeks.
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Old 09-30-2010
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well i allready pump gas @ the same place every day and typically the same time every day between 5 and 6 pm (i work night shift)and i tried 93 for apprx a week and half and had a steady 20 21mpgs and on 87 i can get 22 to 24 and 25.3 was my best so therefore the higher octane hurt my mileage....after a week and half i figured that sufficient time to avg out the mpgs between the 2 different octanes
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Old 09-30-2010
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Quote:
Originally Posted by rpwillix View Post
its a 93 xcab 3.0 ranger auto but JET performance makes a chip for it and thats what im wanting to get
that jet chip is a waste of money i know i have one. a programer is the way to go.
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  #21  
Old 09-30-2010
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anytime an experiment is conducted - it is controlled and done more than one time to out rule an anamoly. Do you really think that this one experience is enough to form a certain conclusion?
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Old 11-19-2010
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A lot of good info here, but the reverse IS true - 93 tune with 87, 89 or 91 octane will perform WORSE. Ford pulls spark globally, so the lower octane will force a MAJOR spark retard. Always use the recommended fuel for that vehicle/tune. Using 89 octane on an 87 tune will not create any additional HP, unless the 87 tune was "too hot" to start with. Regional changes, seasons, fuel supply, altitude, etc make things interesting.
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Old 01-01-2011
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I've run 93 in my truck before for while and I never saw a decrease in mpg.

99,3.0L 4x4. I had a bad pinging and valve chattering problem and I run 93 in it for a while and it goes away. The truck I think performs better, but that's my opinion and not backed by any recorded observations. This was also, I will admit, when I was driving 121 miles back and forth to college on the weekends. The throttle seemed to respond better on the highway.
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