Converted to E85

CovetedStyle · January 9, 2020

Here’s a real noob question because drive train is definitely not something I know a great deal about. I have a 2018 flex fuel truck what is the big deal about E85? Apparently I can run it and it’s at the gas station right next to my house but I never thought much of it. What are the benefits? Having a flex fuel vehicle means I can just fill it up with E85 instead of 91 right? So I mean if it’s better for the truck I’ll definitely start running that instead because it’s a $1.15 a gallon cheaper at the station than 91. Thanks for any info!

Edited January 9, 2020 by CovetedStyle

rastasquid · January 9, 2020

Here’s a real noob question because drive train is definitely not something I know a great deal about. I have a 2018 flex fuel truck what is the big deal about E85? Apparently I can run it and it’s at the gas station right next to my house but I never thought much of it. What are the benefits? Having a flex fuel vehicle means I can just fill it up with E85 instead of 92 right? So I mean if it’s better for the truck I’ll definitely start running that instead because it’s a $1.15 a gallon cheaper at the station than 92. Thanks for any info!

You’ll have a power gain on e85, but less MpG. The big gains in e85 come if you actually do a full tune, you could see a 40+ hp difference between e85 and 91. My old truck was flex and I ran it occasionally, but my new work location has a station with e85 right next door and I didn’t even realize my 2017 isn’t flex, I thought all newer trucks were flex.

CovetedStyle · January 9, 2020

14 minutes ago, rastasquid said:

You’ll have a power gain on e85, but less MpG. The big gains in e85 come if you actually do a full tune, you could see a 40+ hp difference between e85 and 91. My old truck was flex and I ran it occasionally, but my new work location has a station with e85 right next door and I didn’t even realize my 2017 isn’t flex, I thought all newer trucks were flex.

No shit!? Well I definitely have E85 right next to my house and my shop.. but those are literally the only two gas stations in town that have it so if I tune the truck for E85 only I would imagine that it wouldn’t run as well on 91 so if I was out of town that might not work out that great I would imagine. I’m kind of disappointed I just filled my truck up now, I am interested to see what it feels like to run the E85. I wonder if I’ll be able to even tell the difference.

TJay74 · January 10, 2020

19 hours ago, CovetedStyle said:

No shit!? Well I definitely have E85 right next to my house and my shop.. but those are literally the only two gas stations in town that have it so if I tune the truck for E85 only I would imagine that it wouldn’t run as well on 91 so if I was out of town that might not work out that great I would imagine. I’m kind of disappointed I just filled my truck up now, I am interested to see what it feels like to run the E85. I wonder if I’ll be able to even tell the difference.

The truck will run just fine on regular gas or E85, tuned or not. The trucks have 2 separate fueling tables for gas ans E85. The ECM uses a sliding scale system to go between the 2 fuels. You could have a fully tuned gas tune and a fully tuned E85 and the ECM will move back and forth as needed with zero issues. That is the beauty of GM's ECM's and how their flex fuel system works.

CovetedStyle · January 10, 2020

39 minutes ago, TJay74 said:

The truck will run just fine on regular gas or E85, tuned or not. The trucks have 2 separate fueling tables for gas ans E85. The ECM uses a sliding scale system to go between the 2 fuels. You could have a fully tuned gas tune and a fully tuned E85 and the ECM will move back and forth as needed with zero issues. That is the beauty of GM's ECM's and how their flex fuel system works.

That’s rad! I had no clue, it’s why I like floating around on here I learn all these cool things! Thank you for the info it’s greatly appreciated my friend!

CamGTP · January 10, 2020

You're positive it's a factory option on yours?

Is there a sensor inline on the fuel feed line on the frame? Anything after 2014 was pretty much never a factory installed feature.

15GMCALLTERRIAN · December 16, 2020

On 9/9/2019 at 12:05 PM, sensinitas said:

What two hoses for a crew cab?

Anyone figure this out?

Supermofool · February 4, 2021

On 12/15/2020 at 11:49 PM, 15GMCALLTERRIAN said:

Anyone figure this out?

Bringing up an old thread, but I’m looking for these hoses as well. Going to search parts diagrams for them. Lmk if anyone has found them.

lucas287 · February 5, 2021

I'd recommend not using a hose at all. Use this DSX fitting: https://dsxtuning.com/products/gm-fuel-line-push-connect-coupler

Expensive - yes. But I went the hose route and don't like the end result. I had to boil one of the bends to straighten it out and then try many configurations to get it lined up properly. This DSX fitting would be a breeze and would ensure flow isn't compromised. I don't have a wideband to confirm WOT fueling but I know others have complained of reduced flow by going this approach.

Also do yourself a favor and use this harness extension: https://burgertuning.com/products/48-extension-for-fuel-it-flex-fuel-analyzer

lucas287 · February 5, 2021

On 1/10/2020 at 10:46 AM, TJay74 said:

The truck will run just fine on regular gas or E85, tuned or not. The trucks have 2 separate fueling tables for gas ans E85. The ECM uses a sliding scale system to go between the 2 fuels. You could have a fully tuned gas tune and a fully tuned E85 and the ECM will move back and forth as needed with zero issues. That is the beauty of GM's ECM's and how their flex fuel system works.

Just to clarify this statement for anyone who comes across this thread. It's not entirely accurate. Your ECM does indeed have dozens of Flex Fuel tables that are prepopulated from the factory, however, they are not active! You'll need to check a few boxes and change the "stoich fueling against alcohol %" at the very least. Then the ECM will do exactly as TJay says above and interpolate between two tables depending on fuel composition.

Simply dumping e85 in the tank will result in wild fuel trims and a poorly optimized ignition timing map.