Has anyone else had the problem with getting worse mpg running 93 octane then on 87 octane. I tried the search function, but nothing came up.

 

Yeah i tried it once, i think i was using more fuel with Shell V power. Im gunna pull on my truck to the airport one of these days and fill it up with Av. Gas. its 100 octane.

 

i did

on my ranger i get 19-20 on 87 octane and 16-17 on 94 octane

on my motorcycle i get 51 on 89 octane and 40 on 94 octane

 

i have to admit though...i runs great...i can definitely tell a difference between 93 and 89 octane. I just didn't think my fuel mileage would go down

 

Your computer isn't tuned for it

 

Without a tune, you are wasting your money, polluting more and clogging you Cat. If you can tell a difference you are feeling what you want to feel.

http://www.ftc.gov/bcp/edu/pubs/cons...tos/aut12.shtm

~HJ

 

If the truck doesn't need it then don't run it. There was an article in Sport Compact Car like 5 years ago and they dynoed a Honda Accord V6 with the recommended 87 then dynoed it with 91. The engine made 10hp less with the higher octane fuel.

 

What you are feeling is all in your head. It is actually degrading performance. It is degrading your MPG. And if you keep using it, it is going to degrade the rest of your engine with carbon and screw up your entire emissions system.

You computer must be reprogrammed to properly use any octane other than 87.

 

Damit i wish i had known this, i have not done it every single fill up but on multiple occasions i have, on a new truck do you think its done any damedge yet? i have about 5700 miles on it and ive maybe put 93 in...7 times?
getting about 270 miles per tank

 

I doubt it, Just hitting your wallet.

 

I appreciate the info and the article...didn't realize 93 would have that kind of affect...im still pretty sure that it has helped the low end torque just from the way i pull trailers there is a difference...granted it does seem to fall off a little after 2000 rpm compared to normal

 

Butt dyno is usually wrong unless its a major increase in power.

 

umm. what's stated above isnt exactly true. For a while i was using Shell 87 octane fuel. I noticed a rough idle and the tach was sitting well below 1000. Filled er up with Shell V-Power 93 octane and the truck idled higher and smoother.

 

Which means there is something wrong with your engine. You should fix it rather than continuing to make it worse and throwing money in it.

 

i have a superchip, said it needed 92 octane or higher to work right. my truck burns the higher octane fuels to quick, so i actually got better mpg with 87 or 89 octane (regular) then any other grade

 

Look in your manual. It will say 87. Rangers don't have high compression engines or boost. You don't need the extra octane.

 

your truck isn't designed to run 93 octane. its not high compression like a corvette where it needs slower burning fuel. 93 is a little bit thicker so it burns slightly slower than 87. when you have high compression you have more horse power but high compression makes the fuel burn faster. semis run completely off of compression which is why diesel fuel is so thick and thats why semis don't have sparkplugs. your engine assuming it is the stock motor is designed to burn most efficiently on 87 octane and anyting else your basically wasting money.

 

It isn't really thickness. Its chemical composition.

 

Sometimes my 4L SOHC runs rough on regular fuel too misisng every so offten, and my 02 ranger did it as well. Also If I fill up at the cheaper stations it stalls, Shell and Petro Can seam to run smoother though.

 

and....


drumroll please.......


Higher Octane = Lower Energy per volume unit.

 

Higher octane is not slower burning, it has a higher temperature of ignition.

No, but higher octane can advance the timing. The closer to TDC you spark it, the more energy out of it you are going to get. Hence why running E-85 doesnt give a 30% drop in mileage when E-85 has 30% less energy than 87 oct gas. Ethanol has an "octane" rating of 110 IIRC.

 

There is so much misinformation in this post and I hope nobody reads it and believes all of it.

I have never read anywhere that high octane fuel has a temperature of ignition. It does tend to burn slower and more uniformly. It also resists pre-ignition. High octane fuel cannot change timing but advancing the timing is done when using higher octane if the engine does not have higher compression to utilize the higher octane fuel. Advancing the timing is not closer to TDC, it is farther away from TDC.

High octane fuel is not thicker. I use 110 to 112 octane in my race car at 14:1 compression and that fuel is no thicker than 87 octane pump gas.

Be careful about using 100 octane Av-gas. It is my understanding that even though it is called unleaded, it still has a very small amount of lead in it which can damage your catalytic converter. I don't know this for fact but I would recommend investigating this a little before trying it.

The slight miss you get at idle with 87 may just be a lean miss. They run the engine lean to reduce emissions. A slightly rich mixture will will run smoother. Using higher octane will have a tendency to run slightly rich because you don't get a complete burn due to the slower burn. This is hypothetical and may not be fact. Just a suggestion based on a few facts.

 

Aviation fuel is not called unleaded at all. It is called 100LL which stands for 100 Octane low lead. It is in fact leaded gasoline and shouldn't be used in autos designed for unleaded fuel.

Gary, this octane thing comes up a few times a year and i must say it is funny to read all the various misconceptions. I blame the fuel companies advertising. They always call it premium or super or whatever. When in reality, there is nothing premium or super about it other than the cost.

 

Incase you missed automechanics 101, advancing the timing is moving it closer towards TDC. The spark plug fires before the piston reaches TDC.

Knocking happens because of two reasons, hot spots, and charge temperature. Longer carbon chains have a higher temperature of combustion. In theory, longer carbon chains also have more energy, but the way they blend it, there is actually less energy.

Thus, a higher octane will allow you to advance timing which results in a quicker, more complete combustion.

So if you are so dumb as to think that I was saying changing the fuel changes its timing as if spark timing were magic....well god save your soul and perhaps a reading comprehension class and giving people the benefit of the doubt would would benefit you in life.

 

BTW, longer carbon chains also tend to be more viscous and higher in density...so you're wrong there as well. Whether it is actually true in real world application, I doubt.