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Thread: Which fuel is better for 2.5 Turbo engine longevity?

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    Which fuel is better for 2.5 Turbo engine longevity?

    Picked up a CX-5 Sig over the weekend. I understand using regular fuel (87 octane) will reduce the horsepower (I think to around 227HP) and using premium fuel (91-93 octane) will increase the horsepower up to 250.

    My question is, what is the best fuel for the longevity of the engine?

    My initial thought is premium gas optimizes the engine and ignites under less compression.
    However, would this cause additional strain on the engine due to the output?

    Is using regular fuel and reducing the HP output, and possibly reducing overall strain, on the engine the way to go?

    I bought the Mazda because of the torque and lack of turbo lag (which is the same no matter what fuel is used; 300 ft lbs of torque @ ~2,000 RPMs). The overall horsepower isn't necessarily a big deal to me, as long as I have the power to get power at highway speeds, I'm happy. Overall, I want what is best for the engine's longevity.

    Any info is appreciated, thanks!

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    Arrow Which fuel is better for 2.5 Turbo engine longevity?

    Mazda says in the official power curve, it's an "unnecessary spending on premium fuel" by 2.5T owners if they drive mostly under 4,000 rpm, because the power is exactly the same between 87 and 93 octan from 0~4,000 rpm. As long as you use Top-Tier gas such as Shell (I prefer) or Costco, that's the best you can do for engine longevity.

    Quote Originally Posted by shadonoz View Post

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    Structural Member shadonoz's Avatar
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    Quote Originally Posted by LakewoodTuk View Post
    My question is, what is the best fuel for the longevity of the engine?

    My initial thought is premium gas optimizes the engine and ignites under less compression.
    However, would this cause additional strain on the engine due to the output?

    Is using regular fuel and reducing the HP output, and possibly reducing overall strain, on the engine the way to go?
    Sounds like you're overthinking this. Use whichever suits your budget and your butt dyno.

    Any one of a million other things will probably cause you to replace the car before you could wear out the engine from the strain of too much power. It's made to take it.

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    Quote Originally Posted by LakewoodTuk View Post
    Picked up a CX-5 Sig over the weekend. I understand using regular fuel (87 octane) will reduce the horsepower (I think to around 227HP) and using premium fuel (91-93 octane) will increase the horsepower up to 250.

    My question is, what is the best fuel for the longevity of the engine?

    My initial thought is premium gas optimizes the engine and ignites under less compression.
    However, would this cause additional strain on the engine due to the output?

    Is using regular fuel and reducing the HP output, and possibly reducing overall strain, on the engine the way to go?

    I bought the Mazda because of the torque and lack of turbo lag (which is the same no matter what fuel is used; 300 ft lbs of torque @ ~2,000 RPMs). The overall horsepower isn't necessarily a big deal to me, as long as I have the power to get power at highway speeds, I'm happy. Overall, I want what is best for the engine's longevity.

    Any info is appreciated, thanks!
    Top Tier fuel is best, regardless. I personally use 91 octane ethanol free Top Tier. It's a whopping 60 cents more per gallon, or $6-8 more per fill-up, so why not? 23hp extra, yo! I also notice a 1-3mpg gain using E-free gas.

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    Quote Originally Posted by shadonoz View Post
    Sounds like you're overthinking this. Use whichever suits your budget and your butt dyno.

    Any one of a million other things will probably cause you to replace the car before you could wear out the engine from the strain of too much power. It's made to take it.
    The CX5 engine is stoopidly over-engineered. I am honestly astounded any company would dump this level of R&D into a CUV's drivetrain.

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    Quote Originally Posted by yrwei52 View Post
    Mazda says in the official power curve, it's an "unnecessary spending on premium fuel" by 2.5T owners if they drive mostly under 4,000 rpm, because the power is exactly the same between 87 and 93 octan from 0~4,000 rpm. As long as you use Top-Tier gas such as Shell (I prefer) or Costco, that's the best you can do for engine longevity.
    Awesome! Premium is almost $1 more in Ohio (in my area) and they just introduced a gas tax to increase the price further. I'll likely stick to regular then since I don't plan on racing it all the time. I always purchase Shell gas (don't belong to Costco) since I've read it's better than most. Thanks!
    Last edited by LakewoodTuk; 07-10-2019 at 07:27 AM.

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    Quote Originally Posted by shadonoz View Post
    Sounds like you're overthinking this. Use whichever suits your budget and your butt dyno.

    Any one of a million other things will probably cause you to replace the car before you could wear out the engine from the strain of too much power. It's made to take it.
    Probably am and I lol'd at butt dyno. Good points, thanks!

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    Quote Originally Posted by Unobtanium View Post
    Top Tier fuel is best, regardless. I personally use 91 octane ethanol free Top Tier. It's a whopping 60 cents more per gallon, or $6-8 more per fill-up, so why not? 23hp extra, yo! I also notice a 1-3mpg gain using E-free gas.
    I'll have to check and see if I'm getting Top Tier, I think Shell is considered this? It's been awhile since I've had a car I didn't lease so I wasnt as concerned in the past 3 years. I'll have to double check if it's E-Free. Appreciate the feedback, thanks!

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    Shell gas is top tier. GOOGLE TOP TIER to find all TT stations. ED

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    Quote Originally Posted by LakewoodTuk View Post
    I'll have to check and see if I'm getting Top Tier, I think Shell is considered this? It's been awhile since I've had a car I didn't lease so I wasnt as concerned in the past 3 years. I'll have to double check if it's E-Free. Appreciate the feedback, thanks!
    Shell is TT, but I'm 99.99% sure it's E10.

    For reference, I am paying $2.8X/gal for 91 octane TT E0.

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    Quote Originally Posted by Unobtanium View Post
    The CX5 engine is stoopidly over-engineered. I am honestly astounded any company would dump this level of R&D into a CUV's drivetrain.
    LMAO!

    It's that Premium, yo!

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    87 octane on a stocker. Both are gonna be pulling timing and running rich as hell for a safety net anyways, so detonation chances are roughly the same with both.

    The 93 octane may gain 23hp on the top end, but it's still held back by aforementioned safety net...A tuner's dream...

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    I*ve been using 89 non ethanol, and it*s about .50 more a gallon than 87 ethanol.

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    Quote Originally Posted by Unobtanium View Post
    The CX5 engine is stoopidly over-engineered.
    They can't afford to not have this engine work properly, considering it is used across the entire product line. It's their go to engine.
    If it were a badly engineered engine, they'd be in deep doodoo.
    I've driven Nissans over the years, and they're in the same situation with their VQ35 V6 engine.
    It's been used in every Nissan and Infiniti since 2001, and thankfully for them, it's a good engine.
    If it wasn't, Nissan would be up the creek.
    That's why I've been interested in what happens with the 1.5l turbo engine from Honda.
    It's going to be their go to engine for the next 10 years (probably), and if they can't sort out this gas in oil issue, then they're screwed.

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    Quote Originally Posted by NelsonLewis View Post
    87 octane on a stocker. Both are gonna be pulling timing and running rich as hell for a safety net anyways, so detonation chances are roughly the same with both.

    The 93 octane may gain 23hp on the top end, but it's still held back by aforementioned safety net...A tuner's dream...
    Given t he torque, I'd say the leash is as much for detonation control as it is drivetrain component longevity.

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