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*The Electrician*
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*Disclaimer, the entirety of this discussion is based off oem factory tuning and my altitude locally is 3573feet above sea level*

So about 3 weeks ago I decided to take a stab at using Midgrade 89 octane(no ethanol) in my 2017 2.5L Mazda 3 just to see if I noticed any difference. A few days ago I switched back to 87 Octane(no ethanol) and what I found was to be expected but still somewhat shocking to me a newb on the topic of engine tuning ect. Overall during my time using Midgrade 89 Octane I keep feeling like I had a slight dip in my powerband(butt dyno) and having some racing experience I can usually tell when there is a power loss even in small amounts, my butt is very sensitive lol. I also had noticed a small decrease in the distance a tank of fuel would get me. Well after just 1 tank back at 87 Octane I have increased what a tank of fuel gets me by 50km and definitely feels like some amount of power has returned to my very sensitive butt lol. Of course I never recorded any real data beyond the distance a tank of gas will take me, my daily driving habits have not changed during this period so the results are much as I expected. Conclusions, this car is very very specifically tuned for 87 octane and Midgrade 89/91 octane will NOT help you in any way shape or form without a proper tune from OV Tuning, which premium 91 octane would be used. Yes I know this topic has been beaten to death by many very large bamboo sticks, but thought I would refresh it for some of the newer members here. Stick to 87 octane while your on factory oem tuning guys/gals, upping the octane does NOT help, it actually hinders. Peace out, one love M3R :nerd:
 
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SpeedySpeedBoy313
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*Disclaimer, the entirety of this discussion is based off oem factory tuning and my altitude locally is 3573feet above sea level*

So about 3 weeks ago I decided to take a stab at using Midgrade 89 octane(no ethanol) in my 2017 2.5L Mazda 3 just to see if I noticed any difference. A few days ago I switched back to 87 Octane(no ethanol) and what I found was to be expected but still somewhat shocking to me a newb on the topic of engine tuning ect. Overall during my time using Midgrade 89 Octane I keep feeling like I had a slight dip in my powerband(butt dyno) and having some racing experience I can usually tell when there is a power loss even in small amounts, my butt is very sensitive lol. I also had noticed a small decrease in the distance a tank of fuel would get me. Well after just 1 tank back at 87 Octane I have increased what a tank of fuel gets me by 50km and definitely feels like some amount of power has returned to my very sensitive butt lol. Of course I never recorded any real data beyond the distance a tank of gas will take me, my daily driving habits have not changed during this period so the results are much as I expected. Conclusions, this car is very very specifically tuned for 87 octane and Midgrade 89/91 octane will NOT help you in any way shape or form without a proper tune from OV Tuning, which premium 91 octane would be used. Yes I know this topic has been beaten to death by many very large bamboo sticks, but thought I would refresh it for some of the newer members here. Stick to 87 octane while your on factory oem tuning guys/gals, upping the octane does NOT help, it actually hinders. Peace out, one love M3R :nerd:
I concur wholeheartedly.
 

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I don't have a no-ethanol option in my area, but I agree, a higher octane actually reduces my mpg and does nothing regarding power. 87 FTW.
 

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I believe you all. Though i did notice my average MPG went up when using mid grade. But also the engine grumbled louder (obviously) like someone started using a very slightly larger hammer inside there. MPG was lowest ever on BP's 87 octane, which is when i started going midgrade. But hearing a few other ppl testify that "stock works best on 87" i will do that now onward. Thanks everyone. Been wondering whole time :p
 

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I believe you all. Though i did notice my average MPG went up when using mid grade. But also the engine grumbled louder (obviously) like someone started using a very slightly larger hammer inside there. MPG was lowest ever on BP's 87 octane, which is when i started going midgrade. But hearing a few other ppl testify that "stock works best on 87" i will do that now onward. Thanks everyone. Been wondering whole time :p
Also i noticed that RPMS at all speeds was lower, which probably points to higher stress on engine? Or am i over thinking that?
 

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Gearhead
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Best performance at the lowest cost. It don't get any better than that!
I agree with the caveat that one is using Top Tier fuels, for with our current motors we need all the additives we can get from a gasoline.
 

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2018 Mazda 3 GT
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I've tried various octanes and the only difference I've noticed is the reduction in the mpg I'm getting. The car does not feel more responsive at all.

I lose about 20 miles to a tank when using the 89 octane vs. the 87 octane.

I thought it had to do with my driving behavior at first, but after switching back and forth a couple of times, I realized it wasn't that.

I also noticed a slight burning smell when using the 89 octane if I kept the RPMs over 4k for any length of time. This may be normal though, but I didn't notice it as much when using the 87 octane.
CK

Side question: Anyone using fuel additives or cleaners out there?
 

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Working Class Hero
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If you use top-tier fuel, additives and cleaners are a complete waste of money.

Sent from my SAMSUNG-SM-G891A using Tapatalk
 

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Thanks. That is what I thought too.

I went to AutoZone on Monday and saw two different people pouring that crap in their gas tank in the parking lot. I guess people will believe whatever hype or claims are made on the bottle and just go with it.
CK
 

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Working Class Hero
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Andy Granatelli, a long time ago when asked what it was that STP did responded, "it makes me a lot of money".

Sent from my SAMSUNG-SM-G891A using Tapatalk
 

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My observation in Wisconsin is that if I put in 89 octane it seems to start easier & be a little more "happy" in the city when temperatures are in single digits Fahrenheit and lower. My hunch is that it doesn't have to work as much to avoid knock at the low temps. Other than those conditions, I don't notice a difference and normally use 87.
 

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Personal butt dyno experience with two tanks of 87 and two tanks of 93 is that 93 has more power.

It seems to take almost a full tank for the ECU to accept that it has higher octane and advance timing.

I will be doing a before and after dyno when I'm finished with the OV tune. One run on stock ECU parameters then one run OVT, both on 93.

The only way I can see this being settled is someone running two tanks of 93 then when it's almost empty pulling a dyno, filling up with 87, and making another pull.

I won't be doing that since it would leave me with a tank of 87 before my 93 OVT pull.
 

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I've often wonder if the motor works differently with high octane... Mazda for the first time admitted a change with the CX9 having two ratings...

(with 93 octane fuel) 250 @ 5,000 rpm
(with 87 octane fuel) 227 @ 5,000 rpm

I'm looking for a good Android dyno app to run a comparison with my car because like others the butt dyno says better.
 

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They don't even sell 93 octane fuel in my area... We have the option of 87, 89 or 91 octane.

If these engines had more HP, I could understand using the higher octane, but they just don't have enough ponies to warrant it.
CK
 

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Demon Spawn
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Thanks. That is what I thought too.

I went to AutoZone on Monday and saw two different people pouring that crap in their gas tank in the parking lot. I guess people will believe whatever hype or claims are made on the bottle and just go with it.
CK
depends on the cleaner and where you use it. most of the time on the newer cars with direct injection pouring fuel system cleaner in the tank does nothing but waste money. however using seafoam through the vacuum line and in the oil can help keep things moving freer and lubricate the upper end of the motor better plus using seafoam in the vacuum lines is fun and the smoke show is awesome, i soaked an old carbon clogged egr valve in a pot of seafoam from my old 11 3 and came back the next day the liquid was nasty sludgy black but the egr valve was almost spotless and what was left i could easily remove with a tooth brush. so seafoam does actually clean. but using it in gas of modern direct injected cars wouldnt do much simply for the fact that the gas already has cleaners like gerry said and with direct injection the injectors spray directly into the combustion chamber not like older systems that spray fuel over the valves and then into the combustion chamber, this is where you would see benefit of using seafoam in the gas say on a 98 f150 or something. it would clean the valves as it went over them better than the cleaners in the gas would. and another thing about many of the fuel cleaners is most do much of nothing but waste your money. lucas does nothing that i can tell neither does gumout or stp (i soaked old crudded up parts in them and let them sit over night and try to clean them or see how clean they get and they did nothing to them. yet seafoam and berrymans b12 actually soften and loosen hardened carbon and allow it to slide off of parts. those are now the only 2 i ever buy ad i only ever put b12 in the gas every once in a while and use seafoam in the vacuum system every few oil changes and in the oil every change.
 
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