Poor Fuel Economy solved!? Maybe

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2021 CX-5T AWD CE
Just to be clear, there are ethanol-free fuels, but garden variety premium is e10 just like regular. Whether the additive package is better with premium is debated but most think not. Net, net, premium doesn’t buy you no-ethanol and probably doesn’t buy any increase in cleaning additives. It buys you more headroom so the engine doesn’t detune itself and make less power in challenging conditions, which probably happens very infrequently, even on the 2.5t.

- Mark
 
Thanks Mark, you may well have saved me some dough... and therapy fees haha
Ahhh, the perfect world, where we actually get informed and what we are paying for... a guy can dream at least.
 
Whatever fuel you use, the intake valves see none of it.

Octane is a burn retardant. It makes to fuel burn weaker. Sure, you can advance timing, but in these engines I'd never run anything above 87. They all feel slower with premium Subjective, I know.
 

CarpeDiem

Under Pressure
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Superstitions
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2021 Carbon T
Believe me, the turbo 2.5 feels much stronger running 91 versus 87 - I’ve tried it several times. But if you never explore the engine above half-throttle then it probably won’t be noticeable.
 

yrwei52

2016 Mazda CX-5 GT AWD w/Tech Pkg
Contributor
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Plano, Texas, USA
Believe me, the turbo 2.5 feels much stronger running 91 versus 87 - I’ve tried it several times. But if you never explore the engine above half-throttle then it probably won’t be noticeable.
Only if you rev the 2.5T above 4,000 rpm.

D136607B-C2D0-41FB-AE5A-2017CAE2E18F.png
 
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2020 CX5 Signature
I'm confused by the statement that one would never notice any difference between 91 and 87 octane fuel unless you are running the engine about 4,000 RPM.

Isn't the torque at 2,000 RPM for 91 octane almost three times that of 87 octane? And about double at 3,000 RPM?

How can one not notice more torque?
 
I do recall reading the ratings were higher with premium yes. Does it get a more complete burn as well I assume? Something from the past makes me recall something to that effect which would indicate that there would potentially be less chances or deposits being formed?
I had a DI engine before this one and it certainly ran better on premium but man that was a spendy fill up -F150 5.0l engine.
It would be nice to see some scope comparo photos for actual evidence one way or another over the speculation... would save some bux for sure to use Regular 87 but if Premium reduces deposits (potentially expensive repairs/cleaning?) and gives good power it may be worth the cost?
I would like to not have to care (unlimited funding) but where is the fun in that right?
 

CarpeDiem

Under Pressure
:
Superstitions
:
2021 Carbon T
I'm confused by the statement that one would never notice any difference between 91 and 87 octane fuel unless you are running the engine about 4,000 RPM.

Isn't the torque at 2,000 RPM for 91 octane almost three times that of 87 octane? And about double at 3,000 RPM?

How can one not notice more torque?
For actual data rather than “feeling” the thread below shows the difference in acceleration between 87 and 91 with the 2.5 turbo. Again, if you don’t explore the engine above half throttle then you may not see any difference. As far as the NA 2.5, I’d expect very little noticeable difference between 87 and 91, if any.

 

yrwei52

2016 Mazda CX-5 GT AWD w/Tech Pkg
Contributor
:
Plano, Texas, USA
I'm confused by the statement that one would never notice any difference between 91 and 87 octane fuel unless you are running the engine about 4,000 RPM.

Isn't the torque at 2,000 RPM for 91 octane almost three times that of 87 octane? And about double at 3,000 RPM?

How can one not notice more torque?
Read the power curves carefully. Red line is using 87 AKI octane and gray line is using 93 AKI octane on the 2.5T. Both fuels get 310 lb-ft maximum torque @ 2,000 rpm with two lines overlapping up until 4,000 rpm. 87 AKI fuel gets 227 hp maximum horsepower @ 5,000 rpm showing by the red line; whereas 93 AKI fuel gets 250 hp maximum horsepower @ 5,000 rpm showing by the gray line. The overlapping power curves on both horsepower and torque with 2 different octanes up until 4,000 rpm indicate the engine performance will be the same on horsepower and torque up until 4,000 rpm between AKI 87 regular and AKI 93 premium gas.

By releasing this official power curve on the 2.5T, Mazda wants to show “additional high-rpm performance is possible with higher octane”, and “to prevent unnecessary spending on premium fuel, both power ratings are published”.

BA9095A1-09E2-41FC-877B-6B8C0A0D90E3.png
 

yrwei52

2016 Mazda CX-5 GT AWD w/Tech Pkg
Contributor
:
Plano, Texas, USA
If I understand what you are saying, the upper red line shows Torque and the lower red line shows HP. Yes?
The upper red / gray lines (@1,000 rpm) shows torque with the scale to the left; and the lower red / gray lines (@1,000 rpm) shows horsepower. Unfortunately Mazda forgot to put an hp scale to the right of the graph like most people do, which may cause the confusion.
 

CarpeDiem

Under Pressure
:
Superstitions
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2021 Carbon T
If I understand what you are saying, the upper red line shows Torque and the lower red line shows HP. Yes?
Correct. The difference in actual performance data (not dyno charts) shows a real increase in performance when running 91 octane versus 87, but it is nowhere near three times the torque. The dyno chart shows the difference before and after a tune, not just a change in octane.
 

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