E85 + 87 = better than 93?

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HACK BLOCK

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in my first comparison of running e85 its working out to 8 cents a mile cheaper than 93
 

swathdiver

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Well, I think I blew the mix today. Pumped in 7 gallons of E85 and ran over to a nearby Chevron as they were selling 93 less than everybody. Hit every light and had to stop for the entire county's fire department it seemed! Probably burned over a gallon of that stuff off before the 93 went in.

Last fall that Racetrac's E85 was 72% and the other day that Chevron's alcohol content was 5%. Instead of 20%-22% she settled in at 15%. Mileage was up though, 18.4 mpg and it was hot out, starting at 99 and cooling to 95 the further north we went towards home. About an hour's worth of idling brought the mileage down to 15.8 mpg.

I was cruising at 60 in the right lane and punched it til just under 70 mph and picked up 5 degrees of knock retard. Seems like I'm the retard! Should have stuck with straight 93 this time. The octane rating should be somewhere between 94-95 I think and that E85 must've been 51% at best.

Well, we shall see how that tank plays out mileage wise. The last one broke some records for gasoline!
 
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Well, I think I blew the mix today. Pumped in 7 gallons of E85 and ran over to a nearby Chevron as they were selling 93 less than everybody. Hit every light and had to stop for the entire county's fire department it seemed! Probably burned over a gallon of that stuff off before the 93 went in.

Last fall that Racetrac's E85 was 72% and the other day that Chevron's alcohol content was 5%. Instead of 20%-22% she settled in at 15%. Mileage was up though, 18.4 mpg and it was hot out, starting at 99 and cooling to 95 the further north we went towards home. About an hour's worth of idling brought the mileage down to 15.8 mpg.

I was cruising at 60 in the right lane and punched it til just under 70 mph and picked up 5 degrees of knock retard. Seems like I'm the retard! Should have stuck with straight 93 this time. The octane rating should be somewhere between 94-95 I think and that E85 must've been 51% at best.

Well, we shall see how that tank plays out mileage wise. The last one broke some records for gasoline!

So you had 7 gals of E85 and 20ish gals of 93 and still had spark knock? Why would replacing that 7 gals of E85 with 93 help with that? I'm confused!

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

swathdiver

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how do you know the percentages

We're guessing before it goes in and measure it after it goes in. Good scan tools can read alcohol content and you can even buy a little bluetooth obdII adapter and use the torque pro app on a phone to view it and codes.

So you had 7 gals of E85 and 20ish gals of 93 and still had spark knock? Why would replacing that 7 gals of E85 with 93 help with that? I'm confused!

No it was me not thinking right and frustrated. Too much traffic and way too many knuckleheads on the road today. I guess it was just too hot outside for the tune and I only did it once. I really need to record it or have someone watch it while I'm driving, it seemed to pull timing back at the top of the gear or right as I was letting off the gas. Not really a good test, didn't repeat it because of traffic. Did I tell you that I hate traffic? I love to drive but not when people are on the road! Like to be off the road when people are going and coming from work.
 
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