91 E-free, or 91 "up to 10%" for GDI?

[Ws6]

91 octane is "premium" where I live. 93 is $4/gal, and only sold at one station in a 75mi radius, while 91 TopTier fuels run $2.45-2.75 a gal and are readily available. Which leads me to my question...is ethanol-free useful/helpful for a GDI engine (CX5 Turbo)? Or does it even matter? This is as relates to carbon deposits, or anything else?

 

[Revving2Redline]

I use 87 pure daily and occasionally have to use 91 pure. Maybe try a tank or two. If your car sits a lot and there is high humidity/moisture I would suggest pure if possible. Also, you could go back and forth to try to keep the ethanol content in a lower percentage thus lowering the hydroscopic issue. Keep the tank fresh and full often and find a product to clean,protect and prevent like Gumout Multitune.Its got PEA so its a super cleaner and ingredients to protect from ethanol. Stay away from Seafoam;adding that will add alcohol to your tank.

 

[Ws6]

Originally Posted by Marco620
I use 87 pure daily and occasionally have to use 91 pure. Maybe try a tank or two. If your car sits a lot and there is high humidity/moisture I would suggest pure if possible. Also, you could go back and forth to try to keep the ethanol content in a lower percentage thus lowering the hydroscopic issue. Keep the tank fresh and full often and find a product to clean,protect and prevent like Gumout Multitune.Its got PEA so its a super cleaner and ingredients to protect from ethanol. Stay away from Seafoam;adding that will add alcohol to your tank.


I fill up 1-2x per week, so nothing sits. 87 octane only gives me 227bhp. I want ALL the horsepowers, so I use 91. It's not 93 like I should be using for the full 250hp, but I am presuming it gets me close. 240ish or so?

 

[Snagglefoot]

To get the full 250 hp you have to run your engine at the RPM that horsepower was rated at with full boost. For instance, if the engine is rated as 250 HP at 6000 RPM, you need to be at 6000 RPM to get all 250 HP. At any RPM less than that, you will not be getting 250 HP regardless of what octane you run. Power on!

 

[Ws6]

Originally Posted by Snagglefoot
To get the full 250 hp you have to run your engine at the RPM that horsepower was rated at with full boost. For instance, if the engine is rated as 250 HP at 6000 RPM, you need to be at 6000 RPM to get all 250 HP. At any RPM less than that, you will not be getting 250 HP regardless of what octane you run. Power on!

My car has adaptive tuning. It makes 227 on 87 octane, and 250 on 93 octane. I am PRESUMING (dangerous...) that this is a "sliding scale" and not "oh...all or nothing" and that 91 is going to get me a lot more than 87. Multiple owners confirm that this is the case. It sure seems to be, as I am mirroring magazine-test 0-60 times (done on 93) with 91 octane.

 

[Snagglefoot]

Originally Posted by Ws6
Originally Posted by Snagglefoot

My car has adaptive tuning. It makes 227 on 87 octane, and 250 on 93 octane. I am PRESUMING (dangerous...) that this is a "sliding scale" and not "oh...all or nothing" and that 91 is going to get me a lot more than 87. Multiple owners confirm that this is the case. It sure seems to be, as I am mirroring magazine-test 0-60 times (done on 93) with 91 octane.


Sounds reasonable. Can you do your own 0-60 with 87 and then 91, and report back? It would be cool to see the difference.

 

[Ws6]

Originally Posted by Snagglefoot
Originally Posted by Ws6
Originally Posted by Snagglefoot

My car has adaptive tuning. It makes 227 on 87 octane, and 250 on 93 octane. I am PRESUMING (dangerous...) that this is a "sliding scale" and not "oh...all or nothing" and that 91 is going to get me a lot more than 87. Multiple owners confirm that this is the case. It sure seems to be, as I am mirroring magazine-test 0-60 times (done on 93) with 91 octane.


Sounds reasonable. Can you do your own 0-60 with 87 and then 91, and report back? It would be cool to see the difference.

I'd have to put 87 in it to begin with. I may test it out.

 

[y_p_w]

Originally Posted by Ws6
I fill up 1-2x per week, so nothing sits. 87 octane only gives me 227bhp. I want ALL the horsepowers, so I use 91. It's not 93 like I should be using for the full 250hp, but I am presuming it gets me close. 240ish or so?

Sitting shouldn't really matter with modern cars with modern emissions.systems. I've heard of cars that sat around for over year with E10 in the tank, and testing showed almost no degradation of the fuel. I believe the key is that the tank is mostly pressurized with fuel vapor, so there isn't much oxygen or water vapor in the tank. Of course the freshness of the fuel that goes into the tank might be a concern. Not sure how it works with the gas station storage tanks.

Now if you're talking about carbeurated power equipment where the fuel system isn't sealed, then that's different.