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E85 14’ sierra 4.3 Run e85 or stick with regular gass

TwentyEighthNight
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TwentyEighthNight Enthusiast

TwentyEighthNight

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Hello all, ive recently bought a new to me single owner 2014 gmc sierra 4.3 4x4 double cab with 43,000 miles on it. It has flex fuel standard and was wondering wether or not i should run e85. It is available local and pretty cheap, but ive heard that if the truck has ran gas most of its life the e85 would cleanse the deposits and possibly clog the fuel lines or fuel pump. Should it be safe to switch over to e85 ? Or could i just start running 89 since ive also read that its more beneficial running 89 or 93 over 87 due to detonation 

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scrapen Enthusiast

scrapen

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Running E85 will be fine.  MPG will suffer drastically, but that’s because mpg drop vs ethanol increase is very linear.  It comes down to prices of fuel, so you will need to calculate cost per mile.

 

I have found running approx E30 mix gives me a better cost per mile vs just straight e85 in my 5.3, mixing about 7 gal e85 and the rest 87.   I use a scanner for ethanol mix readouts.  Mix is usually E24 or better as I have a 91 oct tune and try to keep it above e20.  E85 can be as low as e50 in winter months.

 

Every engine is different.  There was a study done to push ethanol fuels at the pump and they found the different test cars had varying results w the different fuel mixes….so your results may vary.

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newdude Senior Enthusiast

newdude

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You can run it if you want.  Expect to lose 2-4mpg. 

 

Stock power on 87 is SAE rated 285hp, 305tq.  On E85, SAE rated 297hp and 330tq.

TwentyEighthNight Enthusiast

TwentyEighthNight

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2 hours ago, scrapen said:

Running E85 will be fine.  MPG will suffer drastically, but that’s because mpg drop vs ethanol increase is very linear.  It comes down to prices of fuel, so you will need to calculate cost per mile.

 

I have found running approx E30 mix gives me a better cost per mile vs just straight e85 in my 5.3, mixing about 7 gal e85 and the rest 87.   I use a scanner for ethanol mix readouts.  Mix is usually E24 or better as I have a 91 oct tune and try to keep it above e20.  E85 can be as low as e50 in winter months.

 

Every engine is different.  There was a study done to push ethanol fuels at the pump and they found the different test cars had varying results w the different fuel mixes….so your results may vary.

Yeah ive somewhat done some calculations for cost per mile and found e85 to be cheaper per mile in the end. So you believe its fine running it despite gas being in the tank for 43,000 miles? No problems with the ethanol cleaning the buildup?

TwentyEighthNight Enthusiast

TwentyEighthNight

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52 minutes ago, newdude said:

You can run it if you want.  Expect to lose 2-4mpg. 

 

Stock power on 87 is SAE rated 285hp, 305tq.  On E85, SAE rated 297hp and 330tq.

Those numbers seem so much better imo. Will the mpg loss be just in city driving or highway as well

scrapen Enthusiast

scrapen

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I don’t know from experience of any clogs, but I would think at just 43k you should be fine.
 

Mileage is always affected across the board.  Of about 3 years of logging (12000 miles), E85 has averaged about 15, mixes around 17, and 18 on premium.  


In terms of cost, mixes have saved me 28% at only 8% mpg loss compared to premium, which I record cost of every time for comparison.

 

e85 saved 31% but 20% mpg loss.  
 

I should note all e85 tests were during summer months, and winter months is mostly premium only.



 

 

swathdiver Senior Enthusiast

swathdiver

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Mine first saw E85 at almost 120K.  No problems whatsoever, these engines love the stuff.  It will take several tanks to get up to full strength and for the computers to adjust for it.  

 

We don't care about reduced range unless we need long range, the measure of performance is cost per mile.

 

After five years, the difference in MPGs between gasoline and E85 is between 18% and 24% depending on the average speed for that tank of fuel.

 

My old Gen IV 5.3 gets its best mpgs with an ethanol content of between 15% and 22% or so.  

CamGTP Senior Enthusiast

CamGTP

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I lose more fuel mileage in the city than on the freeway. Gets about 12-13 around town on E60+ and can still do 20mpg on long freeway trips. Regular fuel gets 14-16mpg and 22ish. These are all summer numbers because I do not run that fuel in the winter, gets way too cold here for that.

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