So here is something weird. I put 93 octane in my car and got really bad mpg. I only got 186 miles before filling up again. I put 87 in my car and got about 330 before I filled up. I just put more 93 in and I can literraly watch the gauge go down as the car eats the gas. I know its not a true mpg calculation but I put gas in at 4 gallons left and same trip to NY and back.

Any idea why this could be? I did get a too lean DTC after I fixed my exhaust. But it went away hasn't come back.

 

I thought 87 was bad for the car?

I always put in 91 and average about 300 miles per tank.

 

That's what I thought, but I get terrible gas mileage using high octane, lol. I have used 91/93 at several different gas stations with the same results <200 with ~16 gallons. But, if I used 87 I get over 300-350 miles just off the 16 gallons (I fill up when the light turns on). I changed the spark plugs about a month ago and haven't had any knocks or pings either. So not really sure why it goes through premium fuel like a binge drinker!

 

I'll have to try 89 next time I fill up and see what my MPG does. If it's better, I'll try 87.

 

I noticed same thing-about 20% drop in mileage. Started happening out of the blue sky. Perhaps gas stations adding **** to boost the octane number?

 

i think some gas station go to a winter blend with more ethenal during the winter. I could be wrong, but that might eat into your mpg

 

The station you go to may put more ethanol in the high test. Try going to a top tier station like shell

 

It can depend on your driving style...if you are driving low rpms most of the time you will see better gas mileage with lower octane. As long as it doesn't ping you are ok. The real advantage to higher octane is ability to tune more power but at times where there is little load on the engine it doesn't do much at all.

 

My driving habits were pretty much the same, so that's why I was a little confused. I just want to make sure that it doesn't mean something is wrong with my engine (ie: not burning high octane fuel when it should).

 

I noticed with ethanol l lose two mpg as compared to 100% gas!l only use 93 octane.

 

There's only 1 station in my County with 100% fuel. And it's 40-50 cents more a gallon. Not worth it in my opinion. It's insane. It'd be cheaper to put stabil ethanol treatment in with each fillup

 

if you're just commuting w/ the vehicle its not that big of a deal to keep using 87 or 89

if you are driving fast regularly you should be using higher octane though

 

Yea its crazy the cost of it.Here in jersey 100% 93 is $3.40 a gallon.In tenn regular 87 is $3 a gal. 93 is $3.79. I cant see how 87 is cheap and 93 so high. Ethanol doesnt give as good mpg!

 

100% 93 here is $4.09 right now.