2021 CX-5 CE Turbo - Premium gas required?

[Mazdiod2]

View attachment 331645
Am I reading it wrong, or this illustration suggests that a car reaches EPA mpg at speeds 75-80mph?

This article claimed that by running the formula developed by 'reverse engineering' the EPA test can give the actual mpg at a certain speed. The EPA tests for highway are a mix of suburban/highway driving at various speeds. They don't claim that the formula works perfectly for all cars, and I suspect the CX5 doesn't do as well at higher speeds as a sedan with the same EPA rating.
It does look like a lot of cars might match their EPA rating at a steady cruise speed of 75 or maybe 80 (for the EPA 50 mpg car).
I haven't tried the formula, I don't have a spreadsheet on my laptop.

 

[Lazy2.5]

the answer to your specific question about (improved) fuel economy is: no.

If it is ethanol blended regular vs ethanol blended premium, probably not much difference.

I am consistently averaging about 45MPG while following a mostly conservative driving style, mix of highway, one lane roads, some city driving. I certainly did not get MPG this low before I tuned the car for premium.

I use only ethanol free premium.

 

[N7turbo]

There is probably truth to that. 91 should be ethanol-free.

 

[200955]

If it is ethanol blended regular vs ethanol blended premium, probably not much difference.

I am consistently averaging about 45MPG while following a mostly conservative driving style, mix of highway, one lane roads, some city driving. I certainly did not get MPG this low before I tuned the car for premium.

I use only ethanol free premium.

I am not sure what you mean when you say you tuned the car for premium.

 

[N7turbo]

I am not sure what you mean when you say you tuned the car for premium.

The factory ECU tune is conservative to prevent knocking on 87 octane gas. If you run premium only, you can get the engine tuned to take full advantage of it.

 

[200955]

The factory ECU tune is conservative to prevent knocking on 87 octane gas. If you run premium only, you can get the engine tuned to take full advantage of it.

Never heard of this before. I would think variable cam timing sprockets would compensate if necessary (but not required) as higher octane does not create knock. And I'll guarantee there is no leftover unburned gas on the power stroke - no tuning required. At 13.5 to 1 compression ratio your car will love 91. I think your refering to minimum octane value the engine can tolerate.

 

[200955]

This article claimed that by running the formula developed by 'reverse engineering' the EPA test can give the actual mpg at a certain speed. The EPA tests for highway are a mix of suburban/highway driving at various speeds. They don't claim that the formula works perfectly for all cars, and I suspect the CX5 doesn't do as well at higher speeds as a sedan with the same EPA rating.
It does look like a lot of cars might match their EPA rating at a steady cruise speed of 75 or maybe 80 (for the EPA 50 mpg car).
I haven't tried the formula, I don't have a spreadsheet on my laptop.

The EPA rating is not done on open highways. The final calculation is done on a "chassis dynamometer" with no resistance from head winds or in rare cases in a wind tunnel.

 

[N7turbo]

Never heard of this before. I would think variable cam timing sprockets would compensate if necessary (but not required) as higher octane does not create knock. And I'll guarantee there is no leftover unburned gas on the power stroke - no tuning required. At 13.5 to 1 compression ratio your car will love 91. I think your refering to minimum octane value the engine can tolerate.

No, we're referring to ECU tuning. For example:

Shop Tuning — DRTuned Racing

www.drtuned.com

 

[Lazy2.5]

I am not sure what you mean when you say you tuned the car for premium.

Apologies for the confusion, my NA 2.5L left the factory tuned for 87 octane only. It will still run well on 91 octane, but won't increase the stock HP and torque ratings in any significant way.

When I switched from ethanol blended regular fuel to 91 ethanol-free, fuel economy dropped. Then, tuning the vehicle for premium amounted to another noticeable reduction in fuel consumption, because the engine made more torque at a lower RPM.

In short, switching to ethanol blended premium from regular might amount to some small MPG gains, but, when I calculated the fuel economy difference switching to ethanol-free premium before tuning, it was about 10-15%, meaning that I wasn't actually spending any more on fuel. Again, i attribute this to the fact the fuel had little to no ethanol in it, but the vehicle still seemed to run and accelerate much better, particularly below 2000rpm.

 

[Lazy2.5]

The factory ECU tune is conservative to prevent knocking on 87 octane gas.

While I do agree with this,

If you run premium only, you can get the engine tuned to take full advantage of it.

... Switching to premium should allow the ECU to advance timing as much as it needs to, to take advantage,

Though, getting the vehicle tuned certainly will allow you to take full advantage, yes. Let's have @AL Cx5 input on this.

FWIW, if you can get ethanol-free fuel where you live, use it.

 

[200955]

Apologies for the confusion, my NA 2.5L left the factory tuned for 87 octane only. It will still run well on 91 octane, but won't increase the stock HP and torque ratings in any significant way.

When I switched from ethanol blended regular fuel to 91 ethanol-free, fuel economy dropped. Then, tuning the vehicle for premium amounted to another noticeable reduction in fuel consumption, because the engine made more torque at a lower RPM.

In short, switching to ethanol blended premium from regular might amount to some small MPG gains, but, when I calculated the fuel economy difference switching to ethanol-free premium before tuning, it was about 10-15%, meaning that I wasn't actually spending any more on fuel. Again, i attribute this to the fact the fuel had little to no ethanol in it, but the vehicle still seemed to run and accelerate much better, particularly below 2000rpm.

I think when you really give it a bit of thought, yes, the design and total engine control system is set up for ethanol based fuel. Shell was the only company that still pumped high octane non ethanol gas. I have to use it in my 630HP classic car with a stroker engine. Because the explosive quality for 91 octane is more volatile you should experience more HP's as it burns quicker and has "a bigger bang for more bucks". The ECM always knows the load on the engine and adjust spark and cam timing accordingly to obtain optimal performance. Think of the ECM as MR KNOW IT ALL as it gathers data from multiple sources and adjusts accordingly. The percentage of ethanol in the fuel is the real concern and it litteraly dictates the price as well as performance. Don't believe me, dump an octane booster in your tank and go for a "rip" - you'll see the difference. On a side note, when drag racing the highest octane value we could get was 50/50 High Test mixed with Mid Grade. Go figure.

 

[RedBaron]

Because the explosive quality for 91 octane is more volatile you should experience more HP's as it burns quicker and has "a bigger bang for more bucks".

You have this backward I think. Higher octane gas is LESS explosive, causing less knock and thus allowing timing to be adjusted to allow a higher compression point before spark, and thus gain more power

 

[N7turbo]

Because the explosive quality for 91 octane is more volatile you should experience more HP's as it burns quicker and has "a bigger bang for more bucks".

Other way around--the fuel is more resistant to detonation, which is why you can run more aggressive tunes.

Edit: psych

 

[RedBaron]

Edit: psych

Too slow my friend

 

[Lazy2.5]

I think when you really give it a bit of thought, yes, the design and total engine control system is set up for ethanol based fuel. Shell was the only company that still pumped high octane non ethanol gas. I have to use it in my 630HP classic car with a stroker engine. Because the explosive quality for 91 octane is more volatile you should experience more HP's as it burns quicker and has "a bigger bang for more bucks". The ECM always knows the load on the engine and adjust spark and cam timing accordingly to obtain optimal performance. Think of the ECM as MR KNOW IT ALL as it gathers data from multiple sources and adjusts accordingly. The percentage of ethanol in the fuel is the real concern and it litteraly dictates the price as well as performance. Don't believe me, dump an octane booster in your tank and go for a "rip" - you'll see the difference. On a side note, when drag racing the highest octane value we could get was 50/50 High Test mixed with Mid Grade. Go figure.

I've seen octane boosters with some sort of metals in it, not just ethanol.

At any rate, I use throttle positions in line with what the car was designed for (ie. Light-mid throttle) usually nothing aggressive, at least not regularly but I'll still never fill up with anything else.

I've seen no indication whatsoever after testing both, that my vehicle is better off running ethanol blended fuel.

 

[Odrapnew]

Other way around--the fuel is less resistant to detonation, which is why you can run more aggressive tunes.

Edit: psych

Correction, it's more resistant to detonation.
I think that's what you meant, just said it wrong.

Depending on the vehicle, some can take advantage of the extra octane.
Turbo/supercharged engines seem to be more common to improve performance with higher octane, naturally aspirated not as much (although some can).

CX5 turbo and Ford Ecoboost (just a couple examples I know of) will take advantage of the higher octane. I know the Ford literature states peak performance is with 93 octane for at least some of their vehicles.

 

[AL Cx5]

X2 higher octane slows flame progation allowing more of a combination of higner boost, more timing and/or engine compression.

How does the engine know it has higher octane fuel? Our older ecu didn't know and we had to build a timing map for higher octane.

My experience with DRTuned was positive. David painstakingly adjusted timing over 6 data logs I provided.

Results was better FE and power rigbt where it can be used as a DD.

With this ecu tune, turning vane inlet elbow, varriable flow stock air box CAI and engine grounding we record +33 mpg combo highway, secondary roads multiple times.. This a turbo CX 5. The increase in FE offsets the additional cost of 95 octane fuel.

I did the above mods while tuning with DRTuned. I data logged wot and had Mazda Edit software plot before and after dyno curve. The software numbers showed wheel HP and was good showing percentage change.

 

[RedBaron]

How does the engine know it has higher octane fuel?

Knock sensors.

 

[AL Cx5]

Knock sensors.

Ohg, I assume knock sensors have come a long way. Back in the day, tuners relied on KS to retard timing and melted many a piston.

Further, if the exhaust system was changed on this type sensor it changed the KS senstivity.

I'll change my KS with others engime management sensors at 100k or when the intake manifold is removed to clean the valves.

If the sensor start to read incorrectly but still within the Ecu limits do they read less sensitive? Meaning they don't pull enough timing.

The KS is just a vibration sensor. It looks just like what we used in 2006.

O2 sensors loose sensitivity bit work within the Ecu values. But the Ecu thinks the engine is running lean and adds fuel. This won't melt a piston. Use more fuel for sure.

A KS used to control timing is just a bandaid way of tuning. I'm underwhelmed...

A tuned Ecu has removed some of the safety factor Mazda engineers put in the tune. If the knock sensor has lost sensitivity or the owner changed the overall tune of the car with say after market exhaust, then something catistropic might happen.