E85 + 87 = better than 93?

[HACK BLOCK]

a friend of mine says I could alternate between E85 and 87 when I reach half a tank and it would be equivalent to about 96 octane and save money at the pump. just wanna get everyone's opinion on this cause I don't know much about E85

 

[BlackBearPerf]

What year, and engine size do you have?

As long as your vehicle is Flex Fuel capable you can run E85. I would say E85 is more for power as opposed to fuel economy. With our tuning there is not a specific tune for E85, but the tuner will alter the flex fuel tables so you can run it with our 89/87 tune or 91+. We do tend to see more power running E85 with the 91+ octane tune.

 

[HiHoeSilver]

@swathdiver has extensive info here on all this "gasology". He can link you to a couple threads.

 

[HACK BLOCK]

What year, and engine size do you have?

As long as your vehicle is Flex Fuel capable you can run E85. I would say E85 is more for power as opposed to fuel economy. With our tuning there is not a specific tune for E85, but the tuner will alter the flex fuel tables so you can run it with our 89/87 tune or 91+. We do tend to see more power running E85 with the 91+ octane tune.

2011 Yukon Denali 6.2

 

[HACK BLOCK]

I also noticed I'm running a lot smoother

 

[BlackBearPerf]

2011 Yukon Denali 6.2

Thanks for confirming that. We would not recommend running anything lower than 91 octane for that engine in combination with E85.

 

[swathdiver]

Consider this, your light comes on and you pull up to the pump, you have about 4 gallons of 93 octane fuel left on board. If you pumped in 17 gallons of 87 and 5 gallons of E85, you'd wind up with an octane rating of around 91.38 and an alcohol content of 22% according to the math. I do not know if those 6.2s like that or not, you fellas have to find out which mixture will maximize your fuel economy and keep the octane rating up while saving you a small fortune on fuel costs.

Here's another example: You have 4 gallons of E85 left on board, pump in 5 gallons of E85 and 17 gallons of 87 and you'd wind up with an R+M octane rating of 93.23 with a 34% alcohol content.

If @BlackBearPerf cautions against doing this, I'd like to know their reasons why.

 

[gooffeyguy]

Consider this, your light comes on and you pull up to the pump, you have about 4 gallons of 93 octane fuel left on board. If you pumped in 17 gallons of 87 and 5 gallons of E85, you'd wind up with an octane rating of around 91.38 and an alcohol content of 22% according to the math. I do not know if those 6.2s like that or not, you fellas have to find out which mixture will maximize your fuel economy and keep the octane rating up while saving you a small fortune on fuel costs.

Here's another example: You have 4 gallons of E85 left on board, pump in 5 gallons of E85 and 17 gallons of 87 and you'd wind up with an R+M octane rating of 93.23 with a 34% alcohol content.

If @BlackBearPerf cautions against doing this, I'd like to know their reasons why.

I'd like to know why also. I've mixed 50/50 87 octane and E85. That should give about 96 octane and seems to run fine.

2001 Yukon SLT
2012 Yukon Denali XL
2011 Yukon Denali RIP 5/20/18

 

[swathdiver]

I'd like to know why also. I've mixed 50/50 87 octane and E85. That should give about 96 octane and seems to run fine.

What kind of mileage do you get from that mix Tom?

 

[Fless]

Consider this, your light comes on and you pull up to the pump, you have about 4 gallons of 93 octane fuel left on board. If you pumped in 17 gallons of 87 and 5 gallons of E85, you'd wind up with an octane rating of around 91.38 and an alcohol content of 22% according to the math.

@swathdiver, is that assuming the E85 is 85% ethanol? Ours typically runs quite a bit less than the 85% max content. YMMV (literally)