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-   -   Less mpg on premium vs regular (http://www.hotrodders.com/forum/less-mpg-premium-vs-regular-226866.html)

mitmaks 12-05-2012 06:31 PM

Less mpg on premium vs regular
 
So I filled up my car with premium and some injector cleaner. I got less mpg than I get with regular. I would think I'd get more mpg with premium.
Any thoughts?

tnovot 12-05-2012 06:41 PM

I wouldn't think it would make any noticeable difference. Unless you have a controlled test using differennt octanes several times to get repeatable results, the difference you experienced could be due to whether or not the tank was filled to the same level in each case.
And maybe the fuel cleaner somehow affected the mileage?
Terry

mitmaks 12-05-2012 06:44 PM

I do log my mpg. I hand calculate mpg every fill-up.

tnovot 12-05-2012 06:53 PM

Quote:

Originally Posted by mitmaks (Post 1619573)
I do log my mpg. I hand calculate mpg every fill-up.

Then I'd do a few more tests with premium w/o fuel cleaner so see what happens. Other variables could be differrences in alcohol content (the gas - not you), more stop and go driving, harder accelerations, etc.
Terry

ogre 12-05-2012 07:17 PM

premium gas has more anti knock stuff in it so you can run higher compression engines with more timing
your best fuel will be the lowest grade you can run

sedanbob 12-05-2012 07:29 PM

Premium burns slower than regular - without timing changes the potential benefit is probably being wasted out the exhaust. Ogre has it right.

bondo 12-06-2012 04:35 AM

Quote:

Originally Posted by ogre (Post 1619589)
premium gas has more anti knock stuff in it so you can run higher compression engines with more timing
your best fuel will be the lowest grade you can run

Ayuh,.... Exactly,....

Premium is a Waste of money, unless yer motor Needs the less volatile fuel...

MARTINSR 12-06-2012 02:11 PM

Here is the answer on a thread at ecomodder.com Regular vs. Premium - Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com

As mentioned here, there is going to be no better without a change in timing, and at that marginal.

Check out that forum guys if you want to help your fuel costs. I was blown away at what I learned. Those guys are as good at fuel milage Hotrodders.com is at making hot rods. Believe it, they know MUCH more about that stuff than you can ever imagine!

Brian

Beenaway2long 12-11-2012 11:11 AM

High octane burns colder and needs more compression or timing to fully burn. You'll see higher emissions with that combo too.
Timing is a crutch in this situation. If your cylinder head/piston combo require 36* for regular unleaded to get a clean burn, adding 2 degrees for Premium wont yield ANY additional hp. Match, at best. You didnt change any cylinder pressures with the different fuel. You just lowered combustion temperature.

hpete 12-12-2012 04:17 PM

I do marginally better with 93 over 89 in my tbi pup but it's not worth the extra money. It's around 14.25 vs 13.5 mpg.


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