I saw that someone had asked what happens if you run 91 on a 93 tune and the response was possible detonation.

Where I live they mostly have 91 octane, but the BP stations carry 92. VMS offers a 91 and a 93 tune. Obviously I want to most I can get without causing problems. So would the solution be go with a 91 and play it safe or get the 93?

I apologize in advance if this has already been discussed in another thread.

There have been posts where it was said that the ECM will automatically adjust the timing down if the optimum octane fuel was not used. Were it me, and it will be soon as stations here are about the same, I would tune for 91.

They say you get worse gas mileage if you use a lower octane than tuned for. I would go with the 91 tune.

Thanks for the info.

Does anyone know why I can't get 93 here? When I lived in Dallas it was all 93. Here you can't get it. Is it a supply and demand thing or something else?

Eh...it's the same for me as well. I live about 90 miles north of Dallas in a mainly rural area. Aside from one Mobil station that averages a good 10 cents higher per gallon on price, all stations around here top out 91 octane.

Here in Detroit we have 110 octane at some pumps on main roads and cruiser spots.. :)

Here in Detroit we have 110 octane at some pumps on main roads and cruiser spots.. :)



hmmmm.....

Here in Detroit we have 110 octane at some pumps on main roads and cruiser spots.. :)



Which 99% of the time (probably 100% but you NEVER know around here LOL) is leaded and not good for Cat's or O2's (unfortunately!) ;)

Which 99% of the time (probably 100% but you NEVER know around here LOL) is leaded and not good for Cat's or O2's (unfortunately!) ;)

Excellent point.

Which 99% of the time (probably 100% but you NEVER know around here LOL) is leaded and not good for Cat's or O2's (unfortunately!) ;)

I have a station about 2 miles from me that sells race gas. It is unleaded but I've heard that unleaded race gas is very hard on cats.

It's also highly illegal to pump race gas into a late model car. In fact, the pump nozzle is the old "larger" leaded style so you need an adapter to pump it in the new style cars.

I run it mixed in my 90 Mustang when I use N20 but I have a fuel cell so no problems pumping it right in. Plus the car doesn't have cats.

93 octane in Texas has ethanol (it is about e10). 91 and 92 generally do not. If you are down here check the pumps. Texas law only allows a tiny amount of ethanol (like 5% beore the pump oerator has to have a "contains ethanol" sticker on the pump. Advantage of ethanol is it ups octane, the disadvantages is that it is caustic (but below 15% effect is said to be negligable), and that it has a lower energy content (worse MPG).

Our Governer signed into law that our gasoline has to be at least E-10. It went into effect this year. Still can't find 93 though.