E85 + 87 = better than 93?

[BlackBearPerf]

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 spoke with Justin and he said you would effectively get the same octane rating, but the fuel milage would be terrible doing it that way.

 

[gooffeyguy]

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

Really not sure exactly. I didn't travel any highway trips to get a good highway mpg reading, but mostly around town and to work and back (about 2 miles each way...lol). My Ethanol % was in the upper 30's to lower 40's and the average mpg on the DIC would range from 12-13.3. Usually on full tanks of E85 my Ethanol % would be between 65-75 and the average mpg on the DIC would be in the 10.9-11.9 range driving the same areas/routes

 

[HACK BLOCK]

I did 100miles on straight e85 and only got 2mpg less than my average

 

[swathdiver]

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

No, I figure 80%. The two stations I regularly use are between 72%-80%, well, at least that's how the truck's computer figures it out!

E85 will only ever reach a maximum 83%, the remaining 2% are additives so people don't drink it!

 

[swathdiver]

Really not sure exactly. I didn't travel any highway trips to get a good highway mpg reading, but mostly around town and to work and back (about 2 miles each way...lol). My Ethanol % was in the upper 30's to lower 40's and the average mpg on the DIC would range from 12-13.3. Usually on full tanks of E85 my Ethanol % would be between 65-75 and the average mpg on the DIC would be in the 10.9-11.9 range driving the same areas/routes

Not bad. I've only one tank in my log at 35% (between 26%-50%) and that was while towing. Going to have to try 50/50.

 

[billnparker]

Fuel economy for E85 is 25% lower than straight gas... so if E85 is that much cheaper than E85, then it’s worth it. Why are you blending it? Higher octane? I’ve done long distance comparisons, and the loss of range is what made stay off E85. While ethanol has a higher octane, (apx. 106) when the refiners blend it with gas, they use a lower octane (sub-octane) to blend. I know this because I did it (blending gas for a living). As someone mentioned earlier, the actual ethanol in e85 is not 85%, more likely 75 -80%. So your math ends up being a little fuzzy. Premium gas will give you more power and a little better fuel economy, but generally not enough to offset the 50 cents.gal cost.

 

[BMPNUGLS]

“Premium gas will give you more power and a little better fuel economy, but generally not enough to offset the 50 cents.gal cost.”

My 2016 Denali XL 6.2 consistently gets 2-3mpg better running either Shell V-Power 93 or Phillips 65 93 octane vs 87 or 89 at either pump. Throw a few ounces of Marvel Mystery Oil in w a Premium fill up...and not only does it ‘smooth out’ the engine, feels like slightly more power, and cleans up the works (I feel) when done on a regular basis..it usually nets min 3mpg improvement....I’ll usually run some MMO every 8,500-10K miles for two consecutive fill ups and it’s definitely a difference you can feel for a good 4-5K miles...

I’ve got a ‘best’ mileage of 28mpg numerous times while running 93 and MMO with an ‘average’ of 22/23...verified via the old fashioned calculation as well....couldn’t believe it the first few times!

 

[gooffeyguy]

Fuel economy for E85 is 25% lower than straight gas... so if E85 is that much cheaper than E85, then it’s worth it. Why are you blending it? Higher octane? I’ve done long distance comparisons, and the loss of range is what made stay off E85. While ethanol has a higher octane, (apx. 106) when the refiners blend it with gas, they use a lower octane (sub-octane) to blend. I know this because I did it (blending gas for a living). As someone mentioned earlier, the actual ethanol in e85 is not 85%, more likely 75 -80%. So your math ends up being a little fuzzy. Premium gas will give you more power and a little better fuel economy, but generally not enough to offset the 50 cents.gal cost.

Yes, E85 gets less mileage, but when it's $0.70-$1.00 cheaper per gallon verses premium 91-93 octane (my 6.2l Denali recommended fuel is at least 91 octane), it still ends up costing less per mile to run.

Last week E85 was $2.14/gal and premium was right around $3. When E85 goes up to around $2.40 or premium gets down below $2.70 it's more cost effective for me to fill up with premium.

Why mix it? The higher the ethanol content the less mileage you get out of it. When mixed with the cheaper 87 octane you get higher octane (more power due to increases timing) and a bit better mileage due to less ethanol content (30-40%) and still pay less than what premium 93 gas would cost if E85 is cheap enough.

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

 

[swathdiver]

Fuel economy for E85 is 25% lower than straight gas... so if E85 is that much cheaper than E85, then it’s worth it. Why are you blending it? Higher octane? I’ve done long distance comparisons, and the loss of range is what made stay off E85. While ethanol has a higher octane, (apx. 106) when the refiners blend it with gas, they use a lower octane (sub-octane) to blend. I know this because I did it (blending gas for a living). As someone mentioned earlier, the actual ethanol in e85 is not 85%, more likely 75 -80%. So your math ends up being a little fuzzy. Premium gas will give you more power and a little better fuel economy, but generally not enough to offset the 50 cents.gal cost.

My truck gets better mileage and range with an alcohol content between 18% and 22% compared to Chevron and Mobil 93 octane offerings.

I'd be interested in comparing numbers from your tests.

 

[jeffbco]

2011 Yukon Denali 6.2

Does it matter that the 6.2 is not a Flex Fuel (E85) designed engine?