91 octane vs e85 in flex fuel Tahoe/suburban?

[iboughtatahoe23]

Which of these is better? I wanna save money of course but if 91 octane overall will increase longevity of the vehicle than by all means

Idk if it matters but the winters are harsh and the summers are hot here.

 

[swathdiver]

If you are doing it for cost, it depends on how many cents per mile it costs to run each fuel.

I would not run E85 during the winter, it ought to be E70 for winter but can still be hard to start.

The motors love E85 and take 5 tanks or so to get fully acclimated to it. The engine makes more power, idles smoother, cooler and even the transmission runs better. It's literally like cheap race gas. Oh, it's also a great injector cleaner.

When we are not planning to travel, we run E85. If we need the range, we run 93. I never intentionally run low octane fuel.

Here are the stats for my Yukon XL with the 5.3 motor:

You can see that for all city driving and 70% highway driving for a tank of fuel, the mpg difference is about 20%. Eventually, the faster you go the greater the spread between the two fuels cost wise.

 

[intheburbs]

There's no need to run 91 octane, unless you have the 6.2. Any benefit running a higher-octane fuel than what's required in your owners manual is a persistent internet myth that won't die. 5.3? Run 87 all day every day.

If you have a yellow gas cap, you can run E85, and you might notice a little more power from the engine. You'll also see a significant decline in mileage, likely greater than any cost save.

E85, or more specifically the alcohol in E85, is hygroscopic - meaning it absorbs water. So I would expect some long-term impact in terms of possible/likely increased corrosion in the engine due to the extra moisture.

 

[Marky Dissod]

Which of these is better?

What do YOU mean by 'better'? I know many 'kids' who are perfectly willing to pay MORE for E85 than for 87,
because E85 is moar powa, yo - plus it burns cleaner than petrol.

I wanna save money of course, but if 91 octane overall will increase longevity of the vehicle, then by all means

One of my close personal friends (a professional pcm / ecm / tcm tuner)
stopped paying for 91 octane once it cost 'too much' compared to 87.

My rule of thumb is that if E85 costs AT LEAST 17% less than 87 octane,
then it MAY be worth it to buy E85 instead of 87.
I.E.: In NYC E85 is nearly the same cost as 87, so I usually use 87.
In Long Island, E85 is cheaper by enough that I'll use E85.

Idk if it matters, but the winters are harsh, and the summers are hot here.

Unfortunately, E85 in the winter is E51 - it's only E85 (E83, actually) in the summer.
I wonder what it is in the spring and autumn?
In NYC, price relationship to 87 is pretty much the same year round, which is lame.

 

[petethepug]

On the 5.3L e85 is great as scrubbing bubbles for the t/b and fuel system to remove carbon deposits. When it’s available and priced right, use it. In SD maybe not in the Antarctic months.

On the 09-14 6.2L that need premium, e85 is a magic bullet. Here in SoCal it’s the difference between a $75 vs $140 fill up. Milage drops 20% in city traffic. The motor does downshift faster and runs smoother.

When my daughter got my grampas 01 flex fuel S10 with 32k miles, the 2.2L 4 cyl motor crawled up hills and knocked. We ran e85 for the first time in 23 years last year.

It woke up all 140hp in that tiny Iron Duke motor and stopped its detonation. It finally downshifted going up hills and Rev’d freely through all 4 gears of its 4L60e. Day & night difference. Lost 40 miles per tank in range city driving but saved $20 over reg fuel price per fill up.

 

[B-train]

Lots of good information already provided, so I'll just ad a tidbit more:
1. As stated, unless your 5.3L can run E85 from the factory, you won't see much of an improvement because it's not a high compression motor like the 6.2L. But, you may feel a difference just because of the way E85 burns in the engine.
2. I've been running it in my 2008 6.2L now at a blend of appropriately 30% of total fuel used (if the computer says inused 21 gallons, then 7 of E85 get put in first). Then top the tank with 87. This has proven to be a fun, economical (both cost per mile, and smiles per gallon) way to wake up this animal.
3. The cleaning characteristics are fantastic, and as @swathdiver stated, it takes a few tanks for the ECM to acclimate to it.

So, overall, it won't hurt your vehicle. If you don't have the flex fuel designated engine/PCM then I would experiment with some blend ratios and see what feels good to you and math's out to your liking. I've found a sweet spot for the driving I do with my blend - and some slight tuning of the spark tables and trans shift points.

 

[petethepug]

Now that’s it’s in the cold 40’s here in SoCal, rich start ups on e85 smell like a dirty martini parts cleaner rather than a half cup of 1960’s non catalytic exhaust.

 

[iboughtatahoe23]

If you are doing it for cost, it depends on how many cents per mile it costs to run each fuel.

I would not run E85 during the winter, it ought to be E70 for winter but can still be hard to start.

The motors love E85 and take 5 tanks or so to get fully acclimated to it. The engine makes more power, idles smoother, cooler and even the transmission runs better. It's literally like cheap race gas. Oh, it's also a great injector cleaner.

When we are not planning to travel, we run E85. If we need the range, we run 93. I never intentionally run low octane fuel.

Here are the stats for my Yukon XL with the 5.3 motor:

View attachment 444786

You can see that for all city driving and 70% highway driving for a tank of fuel, the mpg difference is about 20%. Eventually, the faster you go the greater the spread between the two fuels cost wise.

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.

 

[Fless]

E87? Do you mean 87 octane?

 

[Marky Dissod]

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.

 

[PPV_2018]

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.

^^ 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.

 

[iboughtatahoe23]

E87? Do you mean 87 octane?

87 unleaded. I think so.

 

[iboughtatahoe23]

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

 

[B-train]

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.

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!

 

[Marky Dissod]

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

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

 

[Fless]

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.

 

[petethepug]

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

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.

 

[iboughtatahoe23]

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.

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

 

[iboughtatahoe23]

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

My Tahoe is flex fuel.

 

[iboughtatahoe23]

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 hear good things about chevron with Techron