2018 Yukon Denali Flex Fuel?

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

OP
OP
S

Shangaipaddles

TYF Newbie
Joined
Jan 9, 2024
Posts
12
Reaction score
6
if you have flex fuel it will say so on the fuel filler cap/door and you will have the flex fuel rpo code in your rpo list.
they basically only put it on some 2015/2016 then pretty none there after, but you could get lucky. otherwise you can get a decent plug n play kit and just have it turned on in a tune.
this kit should also fit the suv's
That's what I believed to be true as well, which is why I was confused when the AutoSync was showing me ethanol content. I've found a kit that I'll use if I need to, but would be cool not to spend the extra money if I don't have to. We'll see what happens when I put the non oxy in and if the reading changes.
 

B-train

Full Access Member
Joined
Sep 12, 2022
Posts
2,225
Reaction score
3,833
Are you looking to run strictly E85? If not, I would assume you can run up to 50% without any problems. I know the 6.0L engines from 2015 up could run up to 50% ethanol blend right from the factory.

I've done a few tests with my 2017 6.2L, non flex fuel, and it handles a blend up to 50% just fine. No lights or weird running. I did notice that at the 50% range, it seemed like it may have run out of its programming limitations for fuel delivery.

This was a blend of 87 and E85. From what I've seen on both yukons, 08, 17, is that they seem to really like a 20-25% blend of 87 and E85. The power is there due to higher octane, and the mileage doesn't seem to suffer too much. Just an idea.
 

Doubeleive

Wes
Supporting Member
Joined
Nov 7, 2017
Posts
25,949
Reaction score
38,715
Location
Stockton, Ca.
That's what I believed to be true as well, which is why I was confused when the AutoSync was showing me ethanol content. I've found a kit that I'll use if I need to, but would be cool not to spend the extra money if I don't have to. We'll see what happens when I put the non oxy in and if the reading changes.
a lot of gas is e10 which is why
 
OP
OP
S

Shangaipaddles

TYF Newbie
Joined
Jan 9, 2024
Posts
12
Reaction score
6
Are you looking to run strictly E85? If not, I would assume you can run up to 50% without any problems. I know the 6.0L engines from 2015 up could run up to 50% ethanol blend right from the factory.

I've done a few tests with my 2017 6.2L, non flex fuel, and it handles a blend up to 50% just fine. No lights or weird running. I did notice that at the 50% range, it seemed like it may have run out of its programming limitations for fuel delivery.

This was a blend of 87 and E85. From what I've seen on both yukons, 08, 17, is that they seem to really like a 20-25% blend of 87 and E85. The power is there due to higher octane, and the mileage doesn't seem to suffer too much. Just an idea.
Not strictly e85, but want to run any combo of e85 and 93 depending on what is available.
a lot of gas is e10 which is why
Correct, but my truck shouldn’t be able to sense the alcohol content without a sensor.
 

Doubeleive

Wes
Supporting Member
Joined
Nov 7, 2017
Posts
25,949
Reaction score
38,715
Location
Stockton, Ca.
Not strictly e85, but want to run any combo of e85 and 93 depending on what is available.

Correct, but my truck shouldn’t be able to sense the alcohol content without a sensor.
They all detect/show the 10% without a sensor as far I know, I could be wrong
 

Fless

Staff member
Super Moderator
Joined
Apr 2, 2017
Posts
11,702
Reaction score
23,766
Location
Elev 5,280
Many of these later models -- at least the GMT900s -- don't have a physical alcohol sensor -- it's calculated by the engine computer software, based on fuel trim tables.

Are they back to putting sensors in the later models?
 
Last edited:
OP
OP
S

Shangaipaddles

TYF Newbie
Joined
Jan 9, 2024
Posts
12
Reaction score
6
Many of these later models -- at least the GMT900s -- don't have a physical alcohol sensor -- it's calculated by the engine computer software, based on fuel trim tables.

Are they back to putting sensors in the later models?
Well that's interesting. That doesn't seem like a very reliable way to measure it. So if I fill with non oxy and it reads as 0, I still may not have a sensor, but it can sense the alcohol? Not sure I'd want to run full e85 that way.
 

k_arnold72

Member
Joined
Jun 2, 2023
Posts
98
Reaction score
108
Hmm, ok. Thanks. I think my next move will be to fill up with non oxy gas and see if the reading changes. Maybe 9% is just a default value and it’s not actually reading? I still have 3/4 of a tank, so it’ll be a few days, but I‘ll report back.

Like the guys have suggested, maybe try a blend instead of filling all the way up. Just to see if that reading changes. Quarter tank of e85 should be enough to affect the percentage without being detrimental to drivability.
 
OP
OP
S

Shangaipaddles

TYF Newbie
Joined
Jan 9, 2024
Posts
12
Reaction score
6
Like the guys have suggested, maybe try a blend instead of filling all the way up. Just to see if that reading changes. Quarter tank of e85 should be enough to affect the percentage without being detrimental to drivability.
I’d feel more comfortable going lower on the ethanol than higher until we know if it’s reading correctly. I don’t want to run more ethanol than 10% until it’s tuned for it.
 

petethepug

Michael
Joined
May 4, 2016
Posts
2,957
Reaction score
3,187
Location
SoCal
Glad to see you got the a/s. Did you get it to turn off the AFM?

The 2018 Tahoe & Burb 5.3L are flex fuel so it’s still a thing. I almost crab’d myself when I saw a lady filling up a Gen 5 with e85 at the gas station. I didn’t know they still equipped them that late.

It shows the 6.2L didn’t get e85 though. It can be done with a kit I’ve seen on the web. If you have any emission or drive train warranty left be sure to remove the a/s from the truck? Some of the old skool dealership employees that wear tin foil hats are scared shipless of anything without a GM logo.
 

Forum statistics

Threads
132,006
Posts
1,860,772
Members
96,413
Latest member
knometh
Top