Fuel for stock mazdaspeed3

[luckycharms628]

So I just bought a speed3 a week ago it’s a 2008 short ram intake(Cobb) and bilstien shocks, I have no clue if there is a tune or a HPFP on it. I’ve filled it with 93 cause it has a turbo and that’s what my 2011 GTI used. But I’ve been wondering if I don’t hit the gas can I use regular fuel rather than high octane stuff?


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[MSMS3]

In a word - no.

[Carskick]

Only once was 87 in my car. When it was new, I loaned it to my dad and he filled it up for me. Shortly after getting it back, I could tell he did it. Ran like crap. If you stay out of the boost completely, it won't break anything, so in a crunch, sure.

Otherwise, don't do it.

[Db09ms3]

Yeesh, I think it tells you on the fuel door about only using premium. This car is finicky.

FWIW, I had a GT Cruiser prior to my speed and I could use 87 but the ECU adjusted. I only lost power/boost.

[Carskick]

Originally Posted by Db09ms3 Yeesh, I think it tells you on the fuel door about only using premium. This car is finicky. FWIW, I had a GT Cruiser prior to my speed and I could use 87 but the ECU adjusted. I only lost power/boost.

You can tune the ECU to run lower quality fuel. Many modern turbo cars do, but look at their output. It's much lower than it would be if it were tuned for 91/93. Lower octane fuel means less boost/timing.

In many NA engines, tuning from 87 to 93 provides negligible gains, so why bother. In a boosted application, it's totally different.

Look at the new 2.5T from Mazda. It is designed to run on either, so I assume it has a sensor to check the fuel before it goes into the engine, similar to how a flex fuel vehicle can check the Ethanol content. The DISI 2.3 does not do this, it can only react to lower quality fuel by pulling timing or cutting boost. That's why it doesn't run well with lower octane fuel, it's tuned for 91 from the factory.

If you want to tune for 87 oct, contact a tuner and pay for a tune so you can save $.50/gallon and loose 20% of your power output. It's your car.

[Db09ms3]

Originally Posted by Carskick You can tune the ECU to run lower quality fuel. Many modern turbo cars do, but look out their ouput. It's much lower than it would be if it were tuned for 91/93. Lower octane fuel means less boost/timing. In many NA engines, tuning from 87 to 93 provides negelegable gains, so why bother. In a boosted application, it's totally different. Look at the new 2.5T from Mazda. It is designed to run on either, so I assume it has a sensor to check the fuel before it goes into the engine, similar to how a flex fuel vehicle can check the Ethanol content. The DISI 2.3 does not do this, it can only react to lower quality fuel by pulling timing or cutting boost. That's why it doesn't run well with lower octane fuel, it's tuned for 91 from the factory. If you want to tune for 87 oct, contact a tuner and pay for a tune so you can save $.50/gallon and loose 20% of your power output. It's your car.

Well, there's that option too OP. Tune that shit for 87!