What's the best octane to use?

[Kyle_Gates]

Wait Wait Wait!! Before I get "read the 400 million other posts".....

I can't seem to find any solid answers....for Denver.

When I say "best" I just mean, what will perform the best in the car (2018 GT2) at Denver's altitude (basically, 87 or 91?).

(Edit- If driving style matters, generally conservative with the occasional take-down of a punk in his Subaru or Focus, aside from that, average every day driving (the car will never see a track and may not even ever see launch control used)(dont get me wrong I love the Focus ST but not when its a 17yr old behind the wheel whos just bein an jackhole)

 

[19GT-AWD]

... I can't seem to find any solid answers....for Denver.

When I say "best" I just mean, what will perform the best in the car (2018 GT2) at Denver's altitude (basically, 87 or 91?)

Owners Manual says 91 AKI (Anti Knock Index), which is what is used in Canada and the US.

 

[Kyle_Gates]

Ok, I get that. But 91 in Miami = 87(or so) in Denver......(Out here is basically 85/87/91). So then, 87 best here at 5000+ feet or, would I still be better off with 91 at 5000+ feet.

 

[Ahawk1968]

At 4500 ft elevation here, highest octane we can get is 91. Using map 2-3 on the jb4 i add 3.5 gallons of e85 and the car seems happy there. Map 1 or stock , plain old 91 seems the best bet.

 

[MisterMac]

Minimum recommended is 91 and is what you should use, regardless of your elevation.

 

[Kyle_Gates]

91 it is!

 

[SteveCo]

When I say "best" I just mean, what will perform the best in the car (2018 GT2) at Denver's altitude (basically, 87 or 91?).

I don't think you can get an answer to that beside opinion, as there is no empirical evidence available. You'll find people arguing fervently on both sides of the street, so try your own testing and see what results you get. Octane requirements do go down with altitude - how much of a real world impact that has, especially for this turbocharged engine and chassis, is unknown.

We're in the foothills of the Rockies at about 4000 feet, and I find no noticeable performance or mileage differences between 87 and 91 for the type of driving I normally do. As the saying goes, YMMV ...

 

[MisterMac]

He asked about "Best". The OM clearly states we will attain our "best" at 91 Octane and above. That being said, I've also used 87 at 4,500 elevation without any noticeable performance difference as long as I am not jumping on the pedal.

 

[SteveCo]

He asked about "Best".

He asked about "Best" at Denver's altitude.

 

[MisterMac]

The altitude doesn't matter.

 

[MisterMac]

The fuel at your gas station list's the minimum octane within it. Therefor, 91 sold at 5,000 elevation is what your Stinger needs.

The energy needed by your stinger doesn't decrease or increase with altitude. It stays constant.

Therfore, the best performance near Denver will be achieved with 91 Octane fuel sold at that altitude.

My altitude is 4,500.

 

[MerlintheMad]

Ok, I get that. But 91 in Miami = 87(or so) in Denver......(Out here is basically 85/87/91). So then, 87 best here at 5000+ feet or, would I still be better off with 91 at 5000+ feet.

Yesterday, I pulled into a Sinclair at Kamas, at the foot of the Uinta Mountains. They had 85/87/88: no 91 octane. I passed. I'm about to go get Costco 91 right now. I'm sure the Kamas locals don't need 91, because at that altitude 88 octane is "premium" enough for vehicles requiring/desiring premium gasoline. Just like coastal dwellers can get 93 octane, and might look askance on our 91 octane, 91 is good enough if you're going to hang around "up here" for very long.

 

[SteveCo]

The performance 'produced' by the car most certainly changes with altitude, as air pressure decreases. The 'energy' in the gasoline does not - but the cars ability to use it does.

Octane requirement (the fuel's ability to avoid 'knock') decreases with altitude because of the thinning air density - as altitude goes up, air density, engine performance and octane requirements go down. A car that 'requires' 91 octane at sea level for optimum performance may very well not at 5000 feet.

The OP realizes that, which is why he's asking specifically about whether 91 octane will provide 'best' performance at his altitude, with this car - instead of posting to one of the existing thread debating 87 vs. 91 vs. 93, recommended vs. required, etc.

If you have clear evidence that this car performs 'best' on 91 octane fuel at that altitude, great - I'm sure he'd like to see that (as would I). Otherwise claiming it does is opinion - nothing more.

 

[MisterMac]

The performance 'produced' by the car most certainly changes with altitude, as air pressure decreases. The 'energy' in the gasoline does not - but the cars ability to use it does.

Octane requirement (the fuel's ability to avoid 'knock') decreases with altitude because of the thinning air density - as altitude goes up, air density, engine performance and octane requirements go down. A car that 'requires' 91 octane at sea level for optimum performance may very well not at 5000 feet.

The OP realizes that, which is why he's asking specifically about whether 91 octane will provide 'best' performance at his altitude, with this car - instead of posting to one of the existing thread debating 87 vs. 91 vs. 93, recommended vs. required, etc.

If you have clear evidence that this car performs 'best' on 91 octane fuel at that altitude, great - I'm sure he'd like to see that (as would I). Otherwise claiming it does is opinion - nothing more.

If it weren't for the sophisticated adaptive ECU, I'd agree with you.

However, you place limits of this car that simply aren't there

 

[Kyle_Gates]

If it weren't for the sophisticated adaptive ECU, I'd agree with you.

However, you place limits of this car that simply aren't there

......I am pretty sure there's more to it than that.

 

[Mr. Tech]

I just filled up with 93 octane from BJ's wholesale. Then found out after the fact that the reason it's so cheap is because it's not a top tier gas and has a much higher ethanol content.

I'm running a JB4 on Map2. Has anyone else run Map2 on BJ's or similar, high ethanol gas? Would you guys recommend turning the tune off until I fill back up with top tier gas?

 

[StungBlueGT2]

I just filled up with 93 octane from BJ's wholesale. Then found out after the fact that the reason it's so cheap is because it's not a top tier gas and has a much higher ethanol content.

I'm running a JB4 on Map2. Has anyone else run Map2 on BJ's or similar, high ethanol gas? Would you guys recommend turning the tune off until I fill back up with top tier gas?

I avoid anything that’s not top tier gas in general and only use Mobil synergy in my Stinger...

But just curious did the BJs gas say more than “Up to 10% ethanol” like the the top tier stations do? More ethanol helps make higher octane so it would actually help the JB4 perform better and why people use e30 to run Map3 & Map5.

Typically the reason gas stations dont get the top tier rating is mostly because they don’t use enough detergents and fuel additives which allows for more carbon deposits, emissions and lower performance.

I don’t think it would hurt anything to use the BJs gas, but you’ll likely notice poor performance(reduced ignition timing) and/or hesitation. Try it, run some logs and drop back to map1 or map0 if it doesn’t run well.

 

[MisterMac]

I avoid anything that’s not top tier gas in general and only use Mobil synergy in my Stinger...

But just curious did the BJs gas say more than “Up to 10% ethanol” like the the top tier stations do? More ethanol helps make higher octane so it would actually help the JB4 perform better and why people use e30 to run Map3 & Map5.

Typically the reason gas stations dont get the top tier rating is mostly because they don’t use enough detergents and fuel additives which allows for more carbon deposits, emissions and lower performance.

I don’t think it would hurt anything to use the BJs gas, but you’ll likely notice poor performance(reduced ignition timing) and/or hesitation. Try it, run some logs and drop back to map1 or map0 if it doesn’t run well.

You can always add your own fuel injector cleaner to gas that is not top tier and achieve the same results.

 

[Mr. Tech]

I avoid anything that’s not top tier gas in general and only use Mobil synergy in my Stinger...

But just curious did the BJs gas say more than “Up to 10% ethanol” like the the top tier stations do? More ethanol helps make higher octane so it would actually help the JB4 perform better and why people use e30 to run Map3 & Map5.

Typically the reason gas stations dont get the top tier rating is mostly because they don’t use enough detergents and fuel additives which allows for more carbon deposits, emissions and lower performance.

I don’t think it would hurt anything to use the BJs gas, but you’ll likely notice poor performance(reduced ignition timing) and/or hesitation. Try it, run some logs and drop back to map1 or map0 if it doesn’t run well.

Interesting, I wonder if BJsB had is really just 91 or lower octane with just a ton of ethanol to get it to 93. And since it's base is a less clean had, that's why it can't get the top tier rating.

I didn't check to see what it said on the pumpvas far as ethanol content, I just read that it was high online. It's a new gas station and it was my first time there. Next time I drive by I'll see if I can find that info.

I took a couple logs, everything looks fine so far. It was 10 gallons of BJ's mixed with about 6 gallons of Shell 93.

 

[Mr. Tech]

You can always add your own fuel injector cleaner to gas that is not top tier and achieve the same results.

That's a good point. Thanks!