90 octane ethanol free VS regular 87 octane

My father-in-law just introduced me to a site where you can see locations of gas pumps in the U.S. that provide ethanol free gas. After taking a look around my area, I found that there is a station close by that provides ethanol free, however it is 90 octane. My question is whether or not it is worth it. I have a 2003 mazda protege in which the manual says use “87 octane”, but have read online that using a higher octane will not cause damage to my car. Also I have read that ethanol free is better for your car being that it is straight fuel without additives and will keep your car running longer and cleaner. All that being said, is it worth the extra cost to use and continue to use the ethanol free based on just regular e10 87 octane and will there be much of a difference.

Also I tend to travel a lot for my company so if this will increase my fuel economy it would be a big benefit

Measure your gas mileage over the course of two tanks of 87 then two tanks of 90. Compare the difference in mileage to the difference in cost. My guess is that it won’t make much of a difference. A 2003 car will run fine on both fuels.

I don’t think running 90 octane is going to make any difference either.

For what it’s worth, 91 octane is recommended for my Lincolns and I’ve run 87 for going on 15 years and hundreds of thousands of miles with not even a hint of a problem. The mileage remains the same no matter the octane and actually, while visiting CO where 85 octane is available I run that. Oddly enough, the mileage in the mountains on 85 actually goes up about 1 to 1.5 MPG.

As for damage, a higher octane than required will not cause any damage.

As for the cost, you should see slightly better fuel economy with E0 versus E10, as gasoline has more energy content than alcohol. However, this may not be enough to make up for the price difference. What’s the price of each gas?

not sure of the price difference, I’m going by it this weekend so I’ll check and maybe fill up. Right now I can say that on e10 87 octane right now I average about 375 miles before my next fill.

If you want to compare you’ll need to carefully track miles and gallons over a large number of tanks because the difference will be quite small.

The 90 octane without the ethanol…is that marine gas?

It’s probably Unleaded Premium, normally 92 or 93 octane, without the ethanol, which drops it’s octane to 90…If the people selling this removed the ethanol from their Regular Unleaded, the octane would drop to 85 and they could not sell it…One of the properties of ethanol, it boosts octane…To pay extra money solely to avoid ethanol does not make much sense…

Theh reason I asked if it was marine gas is that in some states (and it varies) gas is available for off-road use (farming and/or marine use) that has no ethanol…but because it’s exempt from some gas taxes it’s illegal to use in cars.

I wish I could purchase 90 octane gasoline without ethanol at the pump. My vehicles are fine with 87 octane with 10% ethanol, but not my 2 stroke rototiller. I just spent $4.80 for about a liter of premixed 90 octane fuel that contains no ethanol at a farm store for my rototiller.

I have all kinds of small engine equipment…2-stroke and 4-stroke. It all runs fine on whatever comes out of my local gas-stations pump…Honda, Briggs, Johnson, Poulan, Tecumseh, never had a problem…

Sort of illustrates the “economies of mass”.

ok so while it might not be that big of a difference as far as gaining gas mileage, will it help in increasing my engine life compared to regular e10 87 octane?

“…will be help in increasing my engine life compared to regular e10 87 octane?”


@Caddyman–I never had this problem with any small engine on my equipment until I bought this Earthquake rototiller. My 2 stroke snow blower does just fine on gas from the pump blended with 2 stroke oil in a 50:1 ratio. However, it does o.k. with the premixed non-ethanol fuel. I just wish I had spent a little more money when I bought the tiller and gone for the electric start. However, all the motorized equipment I have starts so easily I saw no need for an electric start.

For those who want to try E0 gas:


Went and filled my tank on friday at a location that has 89 octane ethanol free. Price was 4.05 per gallon. Regular e10 87 costs an average of 3.55 around here. Also places around here like CITGO and convenience stores like sheetz have a free gas card you can sign up for that takes 3 cents per gallon off.


Nice pointer. I went to the one and only gas station in our county on that list and tried to confirm with the employee behind the counter, and while she seemed educated and she was pleasant (not to mention easy on the eyes), she had no clue what I was talking about. I am going to try and go back when the manager is there to confirm.