Here's my question, since alot of gas stations are now putting up to 10% ethanol in their gases(even premium) which octane is going to net the best MPG??(On the SS/TC specifically) Did GM do all their testing with 91? 92? 93? 94? and was there up to 10% ethanol in it??

 

I don't KNOW... but I would bet willing to be they used 91 octane.

I think probably that is the most widespread. California uses 91 I believe. 91 is what I have around here. Occasionally there might be a station that carries 92 and very rarely where I live do I ever find 93. 94? I've never seen it.

A station down the road has 110 racing gas... not that I'd use it. lol

 

110 is sick whn i had my balt it felt a bit more alive

 

All I put in both my cars is 93!!

 

See i knew i wasn't the only one who thought it would be a good idea, i've put mostly 91/92 in my car but i think 93/94 would be better MPG and better for the engine..........i could be wrong tho

 

I usually use 92

 

Probably 91. They recommend premium and most places sell 91. 92, 93, and 94 aren't nearly as common.

 

93 is all you find here in NC

 

nj has 93, you used to be able to get 94 at sunoco but they dropped it.

 

we had 94 til like 1.5 years ago, now we just have 93, or we could drive like 45 minutes to jersey and get 106 or 108 i forget what it is. we also used to go to the local airport(the tiny townie airports) they have race gas, but thats the octane they use for the planes.

 

there is 94 octane on my route to work everyday so i'm going to try it tonight and see how it goes, i can't find 93 anywhere, it's either 91 or 92 at most places, a few have 94

 

Sunoco here in OH has 94 still, along with 93. Basically rule of thumb will be the higher the octane the better the performance, the lower better MPG. So if you want better MPG run the lowest available Premium.

 

IIRC i read somewhere that when they tested for MPG they used 87 since that is what is advertised in the manual. They recommend a minimum of 91 for best performance. In regards to performance, if your timing tables are set for a specific octane (91) then using 93 will not net you higher performance. Rather the threshold of knock will be reduced. Higher octane is less prone to knock. Higher octane with no change in timing or afr will not yield a higher performance. Or atleast not a measurable one....

 

from what i understand, if you put less then the manufacturers recommended fuel rating, the engine will use different timing maps, dump more fuel causing a rich condition in order to prevent engine knock. this will lower engine efficiency and output. always put manufacturers recommended fuel or higher. its recommended for a reason

 

This wouldn't make sense. Like many other have said, over a tank of 87 octane gas you should save $2.00 at your fill up but your mileage should decrease by a few MPG. In the long run it will be cheaper to use premium.

In this engine ...premium = max power and most mpgs. I can guantee GM tested the engine with the fuel that would pass emission and net the most miles per gallon.

 

im sure GM tested with 91 octane as it is the highest octane fuel available at all pumps in the nation. i believe its also what the manual requires for the LNF (i know it does for the LSJ, so i would assume it does for the LNF as well)

 

It would depend on what grade of fuel they used to test economy and performance in. If it was 87 for economy and 91 for performance then it makes perfect sense. Dont know if what i read was truth or not, but i can only go off of what i read....

 

You can get 93 in NJ and a lot of other places.....

 

Always put in 93

 

Some food for thought here.....

Sure this has nothing to do with a Cobalt SS/TC or a Cobalt to begin with but I found this very odd when I tried it.

Back in 2003-2004 in our racing days I used to drive across country from CA to MI / OH / MO / Canada to a few race events. One time, I was in the middle of nowere Texas and the ONLY thing the gas station had was 85oct gas. I was like WTF do I do now... well I filled up the truck with 85oct gas and prayed for the best outcome

Long story short, for some odd reason I eneded up getting 2.1mpg MORE with the 85oct than I had with 87, 89, 91, and or 93 that I tried out on the road trip.

1995 Silverado Dually Big Block 454 pulling a 32ft trailer behind me... my avg. MPG in the truck while pulling is about 7-8mpg.... so in a 6000 mile trip I had plenty of times to test out for best gas milage

On a side note, coming back from OH/MO at the end of 2004 on I-40 through nothern AZ was NOT fun in the truck..... I looked over at the side of the highway at a sign and it said elevation 10K+.... I got a good 4mpg going through the mountain passes


-Karo

 

If you are asking about the best mileage, I do not know what the answer is...however, if you are talking about beating the EPA ratings and asking what GM used to rate the car, that is a silly question...there is a reason they call them EPA (Environmental Protection Agency) ratings...they are rated by an independent government agency...not GM...

http://auto.howstuffworks.com/28004-...-explained.htm

 

110!
haha jet fuel

 

I think thats since lower octane fuels are more likely to combust they actually are more efficient (provided that you don't go so low as to get knock).

 

This is true, lower Octane nets better MPG. It takes more of a higher octane in useage cause it takes more to detonate it. This is why the new E85 stuff doesn't get as good MPG cause it's octane is like 103 or 104.

 

Actually E85 gets significantly worse mileage because ethanol (85% of its weight) has a significantly lower energy density (joules per gram) than gasoline. The energy density doesn't change that much between gasolines with different octane ratings.