Fuels and MPG...

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Just like i said in another post i've tried various gaz brands around here and my cars always seemed to average between 75 to 100 more km on a tankful of Irving Premium... Do anybody knows why a perfectly tuned car can average between 75 to 100 more kms with a tankful of Brand X gaz and not with the others..??? Additive package... or just superior fuel... The only difference between Irving and the other Premiums fuels around here seems to be 92 Octane Vs. Everybody else 91 Octane but it could never do such a big difference by itself...??
confused.gif


P.S. Performance seems to be equal between all brands with maybe a small plus for the Ethanol but with that, the milleage sucked terribly...
 
was that a boo boo? Or did you mean to put this as a new post?

Anyway octane is probably your difference. Modern cars have knock sensors so if you have a knock on 87 or 91 octane and less or no knock at all on higher octanes 92/93 etc then your mileage will typically be better.

I have a pre-ignition problem on my rio which is spec'd for 87, but I get better mileage on 93 do to less ping and less timing retard.
 
It could be the amount of alcohol that is in the fuel, extra octane that doesn't let the power/mileage robbing knock sensor activate, or additives that make the O2 sensor read differently.
 
Or it could be from the different back-pressures the different pumps auto shut-off at, and the inaccuracy of a car's fuel gauge. One station may fill your car to your fuel gauge's FULL mark with 15 gallons and auto stop, while another may get the same fuel gauge reading with 14 gallons when it auto stops.
I'm not saying one station isn't giving you better mileage (is it "kilometerage in metric?). There are just A LOT of variables that need to be accounted for, including differences in station pumping pressures.

Dave
 
It is a common misconception to think that higher octane = more energy. In reality the energy output is roughly the same. Octane is simply a rating to show the resistance of detonation (contributed to activation energy of the mix). Thus you need more energy to detonate a 92 mix then you do a 87 mix. Which in physical chem terms means less energy overall, but we aren't really in a lab here.

Motors specifically not made for higher octane ratings will actually show a decrease in gas mileage when running a 92 octane fuel due to more work needed to ignite the mix. On the flip side a motor rated for 92 octane will perform better when running 92 then 87 due to 92 mix not igniting prematurely due to high compression seen in those types of motors.

To make things all the more complicated is the overall mixture of the fuel. You have to consider the actual physical makeup specifically the carbon-carbon content. The more c-c ratio the more energy output. The more c-h (carbon hydrogen bonds) the less the energy output.

I won't go into much detail about MTBE additive since it is being phased out but it to has its own story.

But I see ethanol everywhere and it is also another factor in MPG. Ethanol will decrease the overall energy output of the mix since ethanol is already partially oxidized. So the more ethanol in the mix the less mpg's you will see. A good example is seen when looking at the mpg's of E85 flex fuel vehicles (worse than gas).

So there are quite a few factors that will play a role in the MPG's you will see.


Also check out:

http://www.weif.net/car/mileagebrandoctane.php
 
Just to let you know, Ethanol decreases your fuel economy between 3-5% depending on the blend in the gas at "10%" mix.

On a car rated 30, that's -1 or -2 mpg. It's significant if you're picky about fuel economy. (I prefered the old MTBE)
 
just plug in a scanguage or data logger and find out. Look at timing, knock, load, tps and find your variance there will be your answer. For me it was less audible ping and more timing even at cruise, considerable more timing.
 
When Shell upgrades it's refinery and introduced Optimax 98 RON to Australia people reoterd gains up to 140kms pertank. First HD fuel available here. Mobil, BP, Caltex followed down the track. My Mazda went from averaging say 370-390kms per tank to over 460-480kms sometimes 500kms per tank around town. I now run Shell V-Power Racing 100 RON. Economy is down as there's so much more power I can't keep my big boot out of it.
 
10% Ethanol mix makes a big difference in my 2000 V-8 4X4 Tundra. Using 89 oct ethanol blend gives me 14 MPG average. 89 octane without ethanol gives me 17 MPG average. I'm not impressed with ethanol, obviously.
 
Well i allready knew Ethanol would decrease my milleage but i tried it too just to compare. As of the octane, would 92 make as much of a difference Vs. 91 in terms of Pre-Igniting my intake charge? Also, i absolutely don't know about fuel formulations but it's the only thing i think could make a gaz perform than another with the same octane content...
 
I remeber seeing a video not too long ago where a Brittish automobile show did a comparison test between octane ratings, and between auto manufacturers as well. Different vehicles with different compression ratios were used as well. It seemed pretty well done, but I don't remember much about the results, or if Brittish formulas are even comparable to U.S. formulas. I do remember thinking that if I owned and operated a vehicle that required premium fuel in England, I would buy Shell V-Power. Maybe someone else that has seen this video can provide a link.
 
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