87 vs 91 Octane?

[Remotecellphone]

You're about to fill up your gas tank for the first time in your Bronco Sport.....will you be using 87 or 91 octane?

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[MattH88]

I went with 91. I will probably do that until I hit 1500 miles. Word is that's around the time it takes to "break in" the engine.

 

[Osco]

Why would anyone think a higher anti knock formula fuel would be beneficial ?
My 1.5 doesn't knock or ping at all, the engine is designed to run on 87 so why defeat the monetary savings of the 26 mpg with a far more expensive fuel ?

 

[magicbus]

I’ve “trained” all of my car’s computers to use low octane, even my Porsche Boxter. Never had an issue and see no reason to change now.

 

[Bdub]

https://www.familyhandyman.com/article/this-is-the-difference-between-regular-and-premium-gasoline/?_cmp=diytipshintsnl&_ebid=diytipshintsnl1272021&_mid=395764&ehid=EBA2151AB244DB48E69FBCA109F4D3213CB3A5C5

 

[Excape]

Why would anyone think a higher anti knock formula fuel would be beneficial ?
My 1.5 doesn't knock or ping at all, the engine is designed to run on 87 so why defeat the monetary savings of the 26 mpg with a far more expensive fuel ?

I agree. The reason higher octane fuels might offer higher horsepower has nothing to do with energy density, rather advanced timing. If an engine runs well with 87 octane in your environment (e.g. temperature, altitude) and your timing is not being retarded, then it is the better choice. The Mazda SkyActiv engines are somewhat high compression and Mazda's recommendations are similar (87 OK, but 91 optimal for max performance). I did extensive testing with my CX-5 over at least ten thousand miles. I couldn't tell any difference in performance and the economy with the 87 is far superior.

 

[McBrideless]

I agree. The reason higher octane fuels might offer higher horsepower has nothing to do with energy density, rather advanced timing. If an engine runs well with 87 octane in your environment (e.g. temperature, altitude) and your timing is not being retarded, then it is the better choice. The Mazda SkyActiv engines are somewhat high compression and Mazda's recommendations are similar (87 OK, but 91 optimal for max performance). I did extensive testing with my CX-5 over at least ten thousand miles. I couldn't tell any difference in performance and the economy with the 87 is far superior.

This is correct. In modern cars it will not hurt your engine to run lower octane (87) but a higher octane allows your engine to tune itself for more power. I think it’s probably best to be consistent in whatever you choose, because it takes some time to adjust.

 

[Bdub]

And if your car sits longer between fill ups the premium should hold up better and not degrade as quickly, correct? It’s also better for the longevity of the turbo (From what I’ve read). Not an expert by any means.

 

[Speedgrizz]

And if your car sits longer between fill ups the premium should hold up better and not degrade as quickly, correct? It’s also better for the longevity of the turbo (From what I’ve read). Not an expert by any means.

Any gas with ethanol will not hold up for long. Learned that over the years from dirt bikes. You get about three months out of gas with ethanol before it starts to turn.

 

[tombstone81]

I agree. The reason higher octane fuels might offer higher horsepower has nothing to do with energy density, rather advanced timing. If an engine runs well with 87 octane in your environment (e.g. temperature, altitude) and your timing is not being retarded, then it is the better choice. The Mazda SkyActiv engines are somewhat high compression and Mazda's recommendations are similar (87 OK, but 91 optimal for max performance). I did extensive testing with my CX-5 over at least ten thousand miles. I couldn't tell any difference in performance and the economy with the 87 is far superior.

Thanks for the insight, Excape. Just brought home my wife's 2021 CX-9 yesterday and haven't done any break-in or driving in it yet...but of course was excited about the prospect of 250-hp versus 227-hp on premium fuel vs regular. If you are not noticing any measurable "head thrown back" excitement in your CX-5 by rolling with premium, then I will save the money too and stick with 87 on both the Mazda and my future Baby Bronc.

 

[Excape]

Thanks for the insight, Excape. Just brought home my wife's 2021 CX-9 yesterday and haven't done any break-in or driving in it yet...but of course was excited about the prospect of 250-hp versus 227-hp on premium fuel vs regular. If you are not noticing any measurable "head thrown back" excitement in your CX-5 by rolling with premium, then I will save the money too and stick with 87 on both the Mazda and my future Baby Bronc.

Well, results may vary depending on your altitude, temperature, regional fuel blend, and probably many other factors. But in my case, the "butt dynometer" didn't record any discernible difference.

That said, you could go a few months on the different fuels and see if your results are different. When I was testing, I disconnected the battery for ten minutes as that resets the fuel trims and forces a relearn.

 

[Osco]

87 is required. 91+ is recommended (for max targeted hp) and other times for best overall vehicle and engine performance.

Yeah I read that but I doubt I'll ever push my engine into that upper zone of 90-95% power.
Flame propagation Is slower with Higher octane I just see no reason for it, never have.
As for 'training an engine' It's an on going thing as the atmosphere Is always in a state of change. I'll trust my Airgate until I hear a knock.

 

[Osco]

I’ve “trained” all of my car’s computers to use low octane, even my Porsche Boxter. Never had an issue and see no reason to change now.

Exactly
The air meter/gate and the software takes care of such things.
In the summer It hot weather pulling a max load or long climbs Ok I could see a higher anti knock fuel formula of 91 but I bet 89 would do the trick.

 

[tRex]

I'm not sure what-all today's cars do -- or specifically the BS engines -- but the simplest thing is for the computer to detect knock and retard the timing, thus decreasing performance. If you mash the accelerator to make up for this, gaining no cost-savings I'd guess over just paying for 91+ octane in the first place. OTOH if always a conservative driver anyway (or never subjecting it to loads like towing, etc.), high-octane isn't needed and mostly a waste of money. High-and-low, they're all detergent fuels, the difference is pre-ignition (knock) deterring, octane-boosting additives. High-revving, high-boost conditions -- these are higher compression, PLUS turbo engines -- need higher octane if your driving creates these conditions.

 

[Wyo]

91 for max horsepower and most of the time ethanol free for best mileage. Not much difference in price once you factor in the mpg with ethanol free 91. Win-win!

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