Ture or false
5 Year Member
Joined: Jul 2014
Posts: 3,565
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From: Everett, WA
I've never put premium in my truck, it's too expensive lol. I bought a new weed whacker, and it said 91 octane only so I used that for a while, then just decided to use the cheap stuff. 2 years later, no difference.
Ok I have a good bit of friends that work on cars/trucks. The thing I am wondering is it true or false to run high octane like premium gas in your car/truck every once in a while. I was told the high octane helps clean the fuel system. I have done it a few times with my f150 and have not seen any problems doing it. I have mostly done it right after a tune up and fluid change.
Senior Member
Joined: Sep 2013
Posts: 1,267
Likes: 85
From: Behind You
FALSE! Using Higher Octaine fuel on this models is just a waste of money unless you reprogram Octane rating set on the PCM.
Ethanol blended fuel absorbs moisture from the atmosphere. Ethanol provides some of the octane rating. When phase seperation occurs your fuel separates into layers of gasoline on top with water and ethanol at the bottom.
Ethanol blended fuel absorbs moisture from the atmosphere. Ethanol provides some of the octane rating. When phase seperation occurs your fuel separates into layers of gasoline on top with water and ethanol at the bottom.
98 F150 5.4L E40D/4R100
Joined: Nov 2006
Posts: 28,530
Likes: 7,636
From: MI
Right, good posts, - if your interested in running higher octane. You can run both since you can run more than one tune same vehicle. Changing tunes isn't difficult. If you have a tuner, most come with 3 tunes (canned) that you can customize. This can be done without changing anything on the vehicle. Most have 3 programs, economy, tow and performance. Each have there own set of AF's and shift points.
Senior Member
Joined: Dec 2013
Posts: 14,975
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From: SE Michigan
Interesting that the OP specifically asks if higher octane fuel would "help clean the fuel system". Not "make it run better". Yet a bunch of responses don't address the question, just a few pointing out that the CLEANING aspect of fuels is not octane-based which is correct, and a bunch bringing up better running which wasn't the question (and which it won't do as correctly pointed out by most).
98 F150 5.4L E40D/4R100
Joined: Nov 2006
Posts: 28,530
Likes: 7,636
From: MI
Member
Joined: Dec 2015
Posts: 57
Likes: 13
From: Grand Junction, CO
This is just flat out not true. There is only one difference between the different grades of gasoline and that is their resistance to premature detonation which is denoted by the different grades they are organized into. If your vehicle was designed to run 87, then putting anything higher than 87 in it will not improve its performance/cleanliness/anything in any sense of the word. If your vehicle states "minimum 89" or "minimum 91 octane" on the fuel door, then running lower octane fuels increases the risk that you will damage your engine as you rev things up. That's it.
There is one, and only one exception to all of this. Depending upon where you live, the higher octane rated gasoline fuels may likely be ethanol free. Ethanol has a lower btu rating than pure gasoline and therefor, if you switch from an 87 rated fuel with ethanol to an 89 or 91 pure gasoline, then you very likely will see an increase in your fuel mileage around the neighborhood of 10%. However, that's due to the absence of ethanol and not the higher octane rated gasoline.
There is one, and only one exception to all of this. Depending upon where you live, the higher octane rated gasoline fuels may likely be ethanol free. Ethanol has a lower btu rating than pure gasoline and therefor, if you switch from an 87 rated fuel with ethanol to an 89 or 91 pure gasoline, then you very likely will see an increase in your fuel mileage around the neighborhood of 10%. However, that's due to the absence of ethanol and not the higher octane rated gasoline.
Member
Joined: Dec 2015
Posts: 47
Likes: 8
I used to believe the exact same thing as you. That is, until I experienced differently. My Jeep is the only vehicle I've owned that has responded this way. No, I can't explain why. I only know that it will get better or worse fuel mileage, depending on the grade of fuel.
While I was studying engineering, I was specializing in automotive design. Before going into the oil industry I had plans to go work for one of the major automotive manufacturers. I've spoken with numerous engineers actually in the industry, I've raced cars on the private Ford proving grounds outside of Detroit, and I have a friend/classmate or two that's apart of the Corvette racing team that just finished 1st and 2nd at the Rolex 24 at Daytona. I'm not saying this to try to impress you, but to let you know you're not talking to some three toothed hillbilly who speaks out of his ***.
In all the years I've been studying/involved in cars and the energy industry, never once have a read a study or seen an experiment where an engine that was designed for a certain grade of gasoline improved its performance by doing nothing other than going to a higher rated octane gasoline and not changing other engine parameters. I believe you when you say your mileage improves, but I am 100% certain that it is due to another unaccounted factor and not because you're running 91 vs 87.
