I know that this topic has been discussed and I have searched it on this site, but in essence of saving time I just wanted to throw my scenario out there.

I found a Cenex gas station here in town that has incredible prices!! And, for some reason Cenex has the highest octane ratings of any gas station that I've found. Here is what they currently offer, prices as of today: reg. unleaded (89 octane)-2.99, midgrade (92 oct) 3.09, and premium (94 oct) 3.19!

For those prices I have been running the 92 octane. But, my gas mileage has been poor (in my opinion), about 15mpg around town driving, with some highway in there too. Well, I found out that Cenex gas uses a very high concentration of Ethynol, probably why it's cheaper.

So, my question is: Would running a gas with high levels of Ethynol affect gas mileage in a negative way?

2002 A6 2.7T

 

If you are asking if higher concentrations of ethanol lower your gas milage then yes.

 

Supposed to burn a little better for the engine though. Very clean burn. Just the same, you're probably breaking even on this moneywise.

 

Ethanol has 25% less power potential so you need 25% more to equal the same extracted power.

Altho Ethanol has a higher flash point thus more oct.it has less potential energy

we have sunoco out here and the 94 with ethanol is much better for performance then standard 93

if you have a chipedturbo car use 94

 

Thanks for all the fast replies fellas! This web-site has been a godsend, my wife is like "what are you doing" every night on the computer, this site is addicting!

As for the fuel issue, I agree it could bea wash on the price. What I mean is that, after giving it some thought, having a high ethynol content in their gasoline is why Cenex can sell it so cheap. Not only is ethynol cheaper to produce, but if people are getting a little less mpg with it that means they'll be back at the pump more often for fill-ups. There in lies the rub. I think I will go to a Cheveron on the next fill up, use their premium, pay the higher price, and see if I get better mileage. If so, then it's a wash, if not then I will go back to Cenex and continue to save a few bucks.

 

Pump the 94 :P
Its just 20c per gallon... here is 20c per litre but this car is meant to be treated right [8D]

 

A lot of stations sell "cheaper" gas but if you read the pump it's often 10% ethanol. I don't get the same gas mileage as with real gas. And I use midrange consistently. There's also a risk that the ethanol can damage rubber seals which is why flexfuel vehicles are made differently. But at 10%, the risk is low.

 

Not to mention your car has probably retarded timing to stop pinging from lower quality fuel, that will affect MPG as well.

 

OP Here: Just filled my car up tonight with a tank of "regular" gas (92 Chevron). I really hope this is the source of my poor MPG, on this last tank of the ethynol gas I only got 14.7 mpg!!!! Even for alot of city driving, I know this shouldn't be the case. I consider myself a normal driver, not to agressive. If it's not the gas, then I must have other issues looming.

I'll let you guys know in a couple of days, Thanks.

 

I get 16.4 - 17.00 l/100km... which is high
I'm not very agressive neither.. just sometimes... but thats kinda high