Cx5 fuel octane recommendations
Senior Member
Joined: Oct 2018
Posts: 10,665
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From: Northern California
"enable monitoring sensors reporting to the ECU" is what you said premium gasoline would do.
logic would dictate the sensors were previously disabled, to be enabled by the premium fuel.
logic would also dictate the 87 octane gas contributed to the disabled sensors.
occasionally using premium gas seems like occasionally using birth control… IMO
if I desired the extra fuel detergent that premium gasoline provides, I would simply add a bottle of it to the gas tank around every oil change. But I purchase only 93 octane gasoline, so no worries on my end.
logic would dictate the sensors were previously disabled, to be enabled by the premium fuel.
logic would also dictate the 87 octane gas contributed to the disabled sensors.
occasionally using premium gas seems like occasionally using birth control… IMO
if I desired the extra fuel detergent that premium gasoline provides, I would simply add a bottle of it to the gas tank around every oil change. But I purchase only 93 octane gasoline, so no worries on my end.
The ECU needs sensor input so you can start and run your engine as well adjust shifting patterns based on sensor input. Effects altering changes in the ECU are things like the gas octane. This is basic first information you learn when training to be an Automotive Diagnostic Technician or in the case a factory Mazda trained mechanic.
Well I hope many read this thread and your responses it sums what you really don't know! Maybe stick to the gas formals at least that I respect what you know up to a point!
Last edited by Callisto; Sep 26, 2025 at 12:15 PM.
Junior Member
Joined: Sep 2025
Posts: 26
Likes: 4
From: U.S.A.
Ok your age is showing...
(joke I am likely older or close to your age believe it or not). 
Sulfur in gasoline will harm a *Catalitic converter. A vehcle *using it would not only run very poorly but fail any tail pipe emission sampling. So either you are just really old and your education in your field of studies dates back to the 1960s ,1970s and early 1980s or you meant to say before CATs were used?
I also have many friends and have posted this that work for various auto manufactures a couple are actually head of the powertrain development departments (1 now retired was the main guy for Chrysler for almost 2 decades.). I can assure you if an special fuel was used they would have mentioned it to me knowing how I am about fuels specifically for my vehicle I professionally have raced for decades in NHRA and SCCA.
(joke I am likely older or close to your age believe it or not). Sulfur in gasoline will harm a *Catalitic converter. A vehcle *using it would not only run very poorly but fail any tail pipe emission sampling. So either you are just really old and your education in your field of studies dates back to the 1960s ,1970s and early 1980s or you meant to say before CATs were used?
I also have many friends and have posted this that work for various auto manufactures a couple are actually head of the powertrain development departments (1 now retired was the main guy for Chrysler for almost 2 decades.). I can assure you if an special fuel was used they would have mentioned it to me knowing how I am about fuels specifically for my vehicle I professionally have raced for decades in NHRA and SCCA.
We were adding sulfur to get it on the high end of the spec, since ordinarily it was well below maximum with our gasoline components. I assume the test fuel needed to be on the high side (sulfur wise) so it would pass with a worst case fuel, which would still be within legal sulfur limits. Do you really believe gasoline contains 0% sulfur?
Even Tier 3 gasoline standards beginning in 2017 allowed 10 ppm of sulfur.
I don’t know what y’all are doing out there in Kalifornia.
Quit talking to me about gasoline… you’re embarrassing yourself.
Senior Member
Joined: Apr 2025
Posts: 423
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From: Padstow
I have no idea what is and isn't in the test fuel but it is spelt out in the ADR test procedure for all manufacturers to use and isn't available at the bowser. I can only assume that it's compounds are designed to ensure all cars tested are done with the same fuel good or bad and tested to the same standard. The NSW government made a rash decision to test all emission cars anually like California so they set up 2 test stations and were doing free emission testing part of the reason was to collect data which they compared to the ADR requirement for differnt year makes and it turned out to such a chaotic stuff up they abandoned the idea. Was it partly because of fuel variations I don't know. . I still remeber 1986 when we first went to catalytic converters our fuel was so bad you could smell a new car a mile away.
Senior Member
Joined: Oct 2018
Posts: 10,665
Likes: 233
From: Northern California
really then maybe you should as well on more then this thread.
Your world is small where mine is global and a lot more real world testing about fuels.
And you dodged the response again about knowing how an ECU works . 😂
Reading this complete thread again the basic question was answered more then once we may see more deleted response from a few of us again.
Your world is small where mine is global and a lot more real world testing about fuels.
And you dodged the response again about knowing how an ECU works . 😂
Reading this complete thread again the basic question was answered more then once we may see more deleted response from a few of us again.
Last edited by Callisto; Sep 25, 2025 at 06:36 PM.
Junior Member
Joined: Sep 2025
Posts: 26
Likes: 4
From: U.S.A.
really then maybe you should as well on more then this thread.
Your world is small where mine is global and a lot more real world testing about fuels.
And you dodged the response again about knowing how an ECU works . 😂
Reading this complete thread again the basic question was answered more then once we may see more deleted response from a few of us again.
Your world is small where mine is global and a lot more real world testing about fuels.
And you dodged the response again about knowing how an ECU works . 😂
Reading this complete thread again the basic question was answered more then once we may see more deleted response from a few of us again.
Even if all your self-proclaimed knowledge were correct, what good is it if most people aren’t interested in being subjected to your inadequate social skills?
Cue the thesis… spoiler, I won’t read it for a smorgasbord of reasons.
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Joined: Apr 2021
Posts: 1,867
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From: Maine
Junior Member
Joined: Sep 2025
Posts: 26
Likes: 4
From: U.S.A.