Class of 2016-Up: Who uses regular and premium gas and do you notice a difference?

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BinDerSmokDat

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2016 CX9 GT AWD
So with 20K on the clock I have run exactly 4 tanks of premium gas through my rig.

The first two were right after I bought it, because I wanted to get a feel for the HP difference.
I never noticed a big difference and went right back to regular.
The other two times were towing long distances and felt it couldn't hurt.
It towed about the same as with regular gas and didn't really see a difference.

I'm currently running a fifth tank through just trying again to see if there is a marked change.

It seems to me that we should be able to FEEL a 10%/23HP difference, but to be honest my "seat of the pants" dyno isn't really feeling it.
Is it because the difference is so close to the redline and with our motors making enough ummph in the mid-range we never really see that "increase?"
 
How long would the ECU need to notice it had premium in the tank, and alter the parameters to use it? 1 tank? 3? Curious on that.

I run mostly regular, as my small-town local gas bar sells lots of regular, but so little premium, I hesitate to put it in my car. A couple of local friends told me they have had "bad gas" issues running their premium. Hard to prove, but it's enough to make me shy away.
The few times I had premium in it, I didn't notice a difference, but I really don't push this thing hard. I just assumed it would take more than one tank to make a difference.
 
I feel a big difference between 87 and 91..... I hate using 87 just due to some inconsistent turbo pressure when accelerating

I noted it here https://www.mazdas247.com/forum/showthread.php?123860062-16-17-0-60-Unleaded-vs-Premium

I have, and can tell you that 91 octane makes a huge difference in drivability over 87.

My observations when using 91:
The engine is smoother
there is less turbo lag
the throttle response is faster
the turbo spools up faster and consistently
there torque down low is stronger
the engine hp is more in the high rpms (over 4000rpms)

What I find disappointing when using 87, is the turbo pressure was very inconsistent. There were times where I would accelerate and there was a depressing lack of torque. I also noticed engine ping a few times while using 87.

I now only use 91 exclusively
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The first 3 months with it I didn't notice much difference... after 10,000kms I noticed the performance of the engine improved probably now that everything is well broken in. Now I feel a very noticeable difference between 87 and 91
 
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Correct me if I'm wrong but I believe the ECU is basing timing off of detecting knocking.
The parameters that can be theoretically tweaked by the ECU are timing, boost pressure, mixture or throttle if it detects knocking.
I'm not sure which one (or combination) the CX-9 uses, just listing the possible parameters.

So if you punch it with regular and the ECU detects knocking, it adjusts parameters.
If you floor it and it doesn't detect knocking, it delivers max performance.

So it should know right away what gas you are using.
Every time I have put Premium in the tank, it has been almost empty. This last time it took 16.7 gals.
I would expect that I would be feeling something after 50 miles.
 
Premium only increases peak HP which is only seen if you were already at highway speeds and punched it to pass or simply accelerate quickly say from 60-80 mph at high revs. Most people probably aren't going to be accelerating hard from already illegal speeds. This is why peak HP numbers are way over rated. Torque is what everyone uses in normal driving.
 
I only put premium on mine. I noticed the slight performance increase, plus I get more mileage per tank. The difference I calculated to be maybe a $1.50 per tank. Worth it.
 
BinDerSmokDat said:
Correct me if I'm wrong but I believe the ECU is basing timing off of detecting knocking.
The parameters that can be theoretically tweaked by the ECU are timing, boost pressure, mixture or throttle if it detects knocking.
I'm not sure which one (or combination) the CX-9 uses, just listing the possible parameters.

So if you punch it with regular and the ECU detects knocking, it adjusts parameters.
If you floor it and it doesn't detect knocking, it delivers max performance.

So it should know right away what gas you are using.
Every time I have put Premium in the tank, it has been almost empty. This last time it took 16.7 gals.
I would expect that I would be feeling something after 50 miles.
Click to expand...

It depends on how aggressively the ECU adds back timing, boost pressure, etc. after it detects knock. If the ECU tries to add timing back quickly, the car will pretty much always be pinging. Most people don't like this, so auto manufacturers don't program the ECU's this way.

In my experience, car ECU's will pull timing immediately when knock is detected. Once the ECU establishes parameters that result in no knocking/pinging, most ECU's will "stay put" and only slowly try to add back timing. I had a Saab with a turbo, and it would reduce the boost pressure immediately when 87 octane gas was used. I'd have to burn through almost a full tank of premium before the boost would get back to full pressure after 1 tank of 87 was run through. On the other hand, I have a Subaru that tries to add timing constantly, so it pings A LOT (like every other stop light, it seems), even with high octane gas.

I'd expect the Mazda would be closer to the Saab, but who knows...
 
have only used regular 87 octane in our 2016 CX-9. power is fine. mileage is meh (21.7 combined mpg on 50/50 city/highway driving).
 
JPL said:
Premium only increases peak HP which is only seen if you were already at highway speeds and punched it to pass or simply accelerate quickly say from 60-80 mph at high revs. Most people probably aren't going to be accelerating hard from already illegal speeds. This is why peak HP numbers are way over rated. Torque is what everyone uses in normal driving.
Click to expand...

Torque is what is most important especially from a stop, but peak HP is also as important for passing at highway speeds.
Here in Toronto the typical speeds on 400 series highways is 120km/h.... most people will pass between 100km/h up to 130,140, and also especially on the on ramps... this is when peak hp is needed.

with 87, this engine downright looses steam after 4000rpms... 91+ helps significantly

Then there is the inconsistency in turbo boost with 87.... sure torque is the same as 91 when the boost is there.... when its not, its slow as a 90's Honda Civic....
 
Yes there is a difference of 23 horsepower between the 87 and 93 octane fuels.

Yes the engine knock and timing ecu and software is very aggressive, and is always trying to advance timing to the pre knock point.

When you switch back and forth between octane grades, you will be mixing or diluting.

Fill a glass to the top with your favorite red wine.
Drink 85% of your red wine from your glass.
Fill glass back to the top again, but this time with WHITE wine.

What color wine is in your glass now?
How many glasses must you drink down 85% and refill until your white wine looks like white wine?
 
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SDL said:
I only put premium on mine. I noticed the slight performance increase, plus I get more mileage per tank. The difference I calculated to be maybe a $1.50 per tank. Worth it.
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I thought premium gas burns faster so you get less mileage per tank or was it the opposite?
 
Yoo said:
I thought premium gas burns faster so you get less mileage per tank or was it the opposite?
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I'm pretty sure the only difference between grades of gas is the anti-knock properties. Certain high efficiency engines can generate more power from premium gasolines but will retard the ignition with lower grade gas, thereby producing less power.

A lower grade gasoline will knock or pre-ignite (start combusting) before a premium grade. It has nothing to do with the energy density of the fuel, per se.


Sent from my iPad using Tapatalk
 
Yoo said:
I thought premium gas burns faster so you get less mileage per tank or was it the opposite?
Click to expand...

Not my case. Try it.
When I put regular gas, the computer estimates the range at about 306. When I add premium, it estimates the range at about 347-350.
 
With gas prices down a little I've been putting 94 in mine and can't say that I notice a difference in any aspect. If it is producing more HP it's not making a difference in acceleration.

Sent from my XT1650 using Tapatalk
 
Man just get water/ meth injection and fill it up with 87 if its cheaper, the added cooled charge of air will compensate for the lack of octane, and keep you IAT in check.

Just finished installing one in my '17 GT and my minor griep is that the 1 gallon tank gets empty every 2-4 days

Setting to start inj = 4.5 psi
Full steam @ 10psi
 
peak HP numbers are way over rated. Torque is what everyone uses in normal driving.
Click to expand...
Yes. No.
Peak HP numbers are put out by the marketing department.
Torque is what makes for good talk around the coffee pot.

What is useful is the power (horsepower) put out at the rpms you're actually running. A fat hp curve with good power at lower rpms makes the car feel powerful. A skinny hp curve with a peaky peak makes for a high hp number in the sales brochures.

I'm pretty sure the only difference between grades of gas is the anti-knock properties. Certain high efficiency engines can generate more power from premium gasolines but will retard the ignition with lower grade gas, thereby producing less power.
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True, thus the higher peak hp with 91 or 92 AKI (anti knock index) gas than with 87 for our Mazda engines.
 
CAREFUL

I have a '16. Over the past few months, I've been moving to 91 and then 93. I'm on my 3rd or 4th tank of 93 - on Monday I experienced a pretty massive computer failure. The car went into limp mode, and I was able to make it home going 15mph. I had it towed yesterday to the dealer, and they're doing a fairly significant investigation into why it happened. They believe it's fuel related, but it's not "bad fuel" - it's something else. While Mazda corporate is trying to figure it out, the local tech said there's no reason to put 93 in the car - anything above 91 is "too rich" and a "waste". He does suggest 91 over 87, though.

I'm currently in a loaner. I'll let you all know what they come back with.
 
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I would be curious on the outcome. If it's not bad fuel (which happens more often than many think), it will be interesting to hear what it was (CPU borking on fuel mix/timing/etc?)
 
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