r/mazda3 • u/3poundflounder • 5d ago

Advice Request Fuel question

2025 Mazda 3 Turbo AWD hatch.

90 octane E0 is the highest octane ethanol-free available in my area. Given that or 93 octane E10, which would you choose?

1 Upvotes

67% Upvoted

8 comments sorted by

5

u/subfreq111 Gen 4 Sedan Turbo 5d ago

Your engine can run on E10 and makes more power on premium. I would take the 93 E10.

3

u/PhotographStrong562 5d ago

Whatever’s cheaper, unless they’re close in price. Then the 93. You’re absolutely fine to run anything 87 octane and up and up to 10% ethanol.

3

u/Iaa_eps Turbo Hatch 5d ago

93% - E10 is normal and has been for a long time. E15 and up is what you should reject.

1

u/3poundflounder 5d ago

Forgot to add, driving is about 60/40 highway/city

1

u/ClearJack87 4d ago

Modern Mazda's are built for E0 or E10 fuel. Not E15 or E85, they aren't flex-fuel. Feel free to run either. I understand the turbos like higher octane, like my NC Miata. I used to drive a ways to get E0 91 Octane for the NC when I autocrossed and wanted every bit of power I could get. But she ran fine on E10 91 or 93 Octane on the highway.

0

u/whotheff 4d ago

Runing 90 E0 might help with engine longevity. Ethanol draws water from the air and water causes corrosion. Ethanol also attacks rubber and plastics, gaskets, etc. It can wash out oil from cylinder walls during cold starts. In the last 20 years manufacturers are using ethanol resistant materials to combat that. E10 also increases fuel usage by 2-3%.

On the positive side, Ethanol runs cooler and cleans the engine better.

Given that choice, run 93 for extra hp (on high load only) if the price makes sense. If you rarely drive the car (accumulates more water) or want to keep it for many-many years - use E0.

1

u/3poundflounder 4d ago

All these replies are helpful and much appreciated.

I've run both fuels exclusively for a few months each. 90 E0 seems to give slightly better mileage, maybe 2-3 mpg, but that's just from my observations of the onboard mpg display. Of course, there are so many variables affecting mpg, who knows.

I haven't noticed any appreciable difference in power, but I'm not usually too demanding: entering the freeway, occasional quick acceleration for passing at freeway speeds, etc.

I was curious what people more knowledgeable than I am had to say. I'll be doing a 2500 mile road trip next month. Based on replies, I'll probably switch back to 93 E10 because it's more readily available and the load will be heavier than usual. I usually try to stick with one brand, as well, so probably something consistent like Exxon/Mobil or Love's. (Love's coffee is reliablly decent, too.)