91 octane vs e85 in flex fuel Tahoe/suburban?

Marky Dissod said:

Gasoline, unless otherwise specified, tends to be G90 / E10: 90% petrol, 10% ethanol.
Some gas stations are even trying G85 / E15: 85% petrol, 15% ethanol.
Very few gas stations serve G100, ethanol free gasoline, luckily you know when you're getting it, they brag about it.

Never seen E30, or E87.

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^^ This. All “regular” gasoline is maximum 10-15% ethanol by volume. It says so on the pump which concentration you’re actually getting. (Well, it’s supposed to.. ) Some stations/areas it’s 10%, others it is 15%.

Some gas stations do sell ethanol free fuel. There is a gas station close by to me that does. If you have a boat or a car with a carburetor, that’s the gas station to go to. That way you don’t have ethanol gunking up the jets of your carb. .. especially if it does not get run often. The “ethanol free” fuel has its own nozzle, basically instead of the green diesel it’s a blue ethanol fuel nozzle. Oh yea, it’s rated 87 but cost as much or more than 91 or 93 “premium” gasoline, so there’s no mistaking it.

Fless said:

E87? Do you mean 87 octane?

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87 unleaded. I think so.

Looks like everyone is saying e85 for the most part. Maybe run 87 in winter and e85 in warmer months? I do have flex fuel LMG

iboughtatahoe23 said:

Thanks for the info. What’s your opinion on E-30, more specifically in the winter. And is it bad to switch between fuel types each tank just seeing if there’s any differences? I’ve tried e85 (my go to as it’s cheap) I’ve tried 91 octane, e87 and e30. I feel like 91 idles smoother but could just be placebo.

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I've never had an issue. I like the E30 pumps when I can find them, kinda takes the thinking out of it. From what I've learned over many years of trial and error is that bouncing around between blends, octane, etc won't give good data. Commit to 3 or 4 tanks with each one. Do city driving and highway with each tank, let the ECM learn the fuel trims, etc.

Doing this will help you get a real feel for how your truck acts. For example (x2 actually)

1. I ran an almost full tank of E85 in my 2008 Denali (non flex fuel). It ran FREAKING AWESOME!.......until I got a lean code. It still ran awesome with the code, but the injectors couldn't keep the ECM happy at their 14.7 to 1 ratio. Personally I don't think this is an issue knowing all new vehicles run richer to keep the cats hot. So.....I may try that again next summer. It was unbelievable how it woke it's ass up.
2. I tried a 30% blend in my 2017 Denali with the 6.2L direct injection motor. It too LOVED it, and I got 19 mpg on the highway going 80 mph. I have experimented with my traditional 30% blend in it as well and have noticed I've only lost about 1 to 1.5 mpg while gaining more power. But, since it's the wife's DD, I can't bank on good data, or correct blends. When she gets a new vehicle, then I'll learn more on this one.

Moral of the story: E85 is just fine, a check engine light is fine, the over rich calibrations can actually work to your advantage on a non flex fuel vehicle.......just get a piece of tape for that pesky light and viola!

iboughtatahoe23 said:

Looks like everyone is saying e85 for the most part. Maybe run 87 in winter and e85 in warmer months? I do have flex fuel LMG

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Gotta do your maths. If 91 octane is more than 20% more expensive than 87 (25% more for 93),
blend E85 with 91 (93) until it's just cheaper than 87.


Clearly this will NOT work if 91 or 93 or E85 is too expensive compared to 87. Do your maths.
Worst case scenario, you remember you live in NYC, where E85 is not worth a damn in the winter because it's actually E51.
Best case scenario, you learn how to blend 91 or 93 with E85 for less per gallon than 87.
Mid case scenario, you blend 87 with E85 when the price is right, and your engine lasts a lil bit longer,
especially if you can add any of the following just before long trips:
Chevron Techron Concentrate Plus 01154100-5179P
Gumout Regane High Mileage Fuel System Cleaner
Gumout All-In-One Complete Fuel System Cleaner
Lucas Oil 10512 Deep Clean Fuel System Cleaner
Gumout Regane Complete Fuel System Cleaner
Red Line SI-1 Complete Fuel System Cleaner

I run E85 (actually E69 as measured) year 'round, usually at 6,000 ft AMSL (Denver, CO area), with no starting or other driveability issues. Fuel trims are great and I do an occasional trip to the high country, summer and winter.

Get the conversion kit. The 6.2L in the L92 Denali was already a screamer. I remember it would make the suspension feel like it was lifting when the foot was put to the floor on ours.

Can’t imagine what it would have done on 100% e85.

B-train said:

1. I ran an almost full tank of E85 in my 2008 Denali (non flex fuel). It ran FREAKING AWESOME!.......until I got a lean code.

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Fless said:

I run E85 (actually E69 as measured) year 'round, usually at 6,000 ft AMSL (Denver, CO area), with no starting or other driveability issues. Fuel trims are great and I do an occasional trip to the high country, summer and winter.

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So you’re running e85 year round even in sub zero temps? It gets VERY cold here in NESD

petethepug said:

Get the conversion kit. The 6.2L in the L92 Denali was already a screamer. I remember it would make the suspension feel like it was lifting when the foot was put to the floor on ours.

Can’t imagine what it would have done on 100% e85.

eFlexFuel E85 flex fuel conversion kits - eFlexFuel Technology

eFlexFuel E85 flex fuel conversion kits let your vehicle to run on high-octane American E85 fuel.

eflexfuel.com

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My Tahoe is flex fuel.

Marky Dissod said:

Gotta do your maths. If 91 octane is more than 20% more expensive than 87 (25% more for 93),
blend E85 with 91 (93) until it's just cheaper than 87.


Clearly this will NOT work if 91 or 93 or E85 is too expensive compared to 87. Do your maths.
Worst case scenario, you remember you live in NYC, where E85 is not worth a damn in the winter because it's actually E51.
Best case scenario, you learn how to blend 91 or 93 with E85 for less per gallon than 87.
Mid case scenario, you blend 87 with E85 when the price is right, and your engine lasts a lil bit longer,
especially if you can add any of the following just before long trips:
Chevron Techron Concentrate Plus 01154100-5179P
Gumout Regane High Mileage Fuel System Cleaner
Gumout All-In-One Complete Fuel System Cleaner
Lucas Oil 10512 Deep Clean Fuel System Cleaner
Gumout Regane Complete Fuel System Cleaner
Red Line SI-1 Complete Fuel System Cleaner

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I hear good things about chevron with Techron