I'm getting close to 6,000 miles on my 8 and I've been experimenting with different brands of regular gas. I've switched to 87 octane regular and I can report it works great.

Of all the brands of gas I've tried, Shell Regular seems to work the best. The worst I've tried was Costco gas; Sam's Club gas was okay, not bad but not terrific either. Chevron was good but not quite as good as Shell. Engine performance seems to have an extra bit of sparkle when using Shell. And I can feel it within 10 minutes of driving after filling up with Shell. None of the other brands have that sparkle to them. Mileage is improved a bit too. I'm averaging 19.8 mpg with a 50/50 mix of street and freeway driving. I was getting about 18.1 with Premium so I've picked up about 1.7 mpg by switching to regular.

I think the gas is probably burning a bit more efficiently but I also know that I'm not pushing on the pedal as hard to get it to go. Before it would surge when I pressed the pedal; now it leaps.

I've never had a car that feels like an extension of you the way this one does. I think it's a brilliant piece of design and craftmanship by Mazda and I'm quite happy with mine.

Ole Spiff

 

i use amoco almost exclusively and sometimes texaco but here is a shell close by too but not on the way to work which is when i usually fill up. very tank has been 91 or above. please explain, if you know, how 87 octane results in better mileage and causes your 8 to leap rather than surge. i will make the change to 87 if it won't do any harm.

 

I used 91 octane for the first 5,000 miles because that's what was recommended. But after reading in another area on the forum about what others were experiencing using 87 regular, and how rotaries ran better using 87, even in racing, I decided to try a tank and see for myself if it made any difference. I noticed a change in performance within 20 minutes of my first tank of regular (which was Shell Regular). I gassed up by my house and drove down city streets to the freeway (I live in So Calif) and when merging into traffic I pulled around a truck and accelerated. Instead of the usual "push" I noticed the car jumped the moment I pushed the pedal. The reason I remember this so clearly is I was quite startled at the sudden change. I'd driven this car for 5,000 miles and I've already gotten comfortable with how it feels and sounds; it hadn't done this before. It's smoother to drive from a stop and shifting/accelerating is smoother.

When I say "surge" I mean using 91 octane I'd have to push the pedal several inches to feel a push of acceleration. With Shell 87 Regular, the moment I start to push the pedal the engine responds instantly and acceleration "leaps". This feels more like high-performance Chevy V8's. With 91 Octane it has that slight hesitation; that "mushy" feel the way Ford's do when you push the gas pedal.

As far as mileage goes, I noticed with the first tankful of Regular that instead of having to gas up every third day, I went 5 days before having to refill. I then measured the next tankful and got 19.7 mpg. I was getting high 17's to low 18's with 91 octane gas.

I can feel no loss in power using 87 instead of 91 and a definite improvement in engine responsiveness. Gas mileage is measurably improved and I'm saving about 18 cents per gallon by using Regular instead of Premium gas. Now this is on an engine that was already broken in on 91 octane Premium; I don't know if that matters since I didn't break it in using 87 Regular. All I know is it now performs better with Regular. I've been using 87 octane for weeks and the car runs beautifully.

I have a 6sp MT.

Ole Spiff

 

I've been wondering. Does Ford's influence come into play here?

Fords are notoriously addicted to higher octane gas. They always ping like the dickens if you try regular gas in them.

You think it's possible that Mazda is following an order from Ford on this?

Oh yeah, I've been religiously using 93 types, exept for like $3 of regular to get me to a better station. That $3 of regular (87) ran just as good. I don't know about "better", it was too little to tell.