E85 in non-FlexFuel 5.3

[6sigma]

I have a 2015 Sierra 5.3 that does not have the $100 FlexFuel E85 option. I've had FlexFuel trucks before this, and like the option to run E85, but this truck does not have the option. All 2014 5.3s are E85 capable, and the 2015s have it as a standalone $100 option. I did some research on what exactly the $100 option gets you, and I'm pretty sure it is just the yellow colored gas cap. According to GMpowertrain.com, and all parts information I can find, there is NO difference between the E85 and non-E85 5.3. GM Powertrain says the 5.3 is E85 compatible, period.

 

So, I decided to run a couple tanks of E85 to see what happens. Turns out, it runs E85 exactly as I would expect and have seen from my previous FlexFuel trucks. It cranks a little longer on cold start, as others have reported. It get less MPG, maybe 20% less. It idles smoother and feels much more responsive than on 87 octane gas. I had to pull out into 50mph traffic from a stop so I hit the gas pretty hard, the truck smoked both rears and stepped sideways a little bit. It is not that responsive on 87 gas.

 

I also noticed that the truck seems to hold higher gears more, rather than downshift early. I think on 87 octane gas it will downshift much sooner as an anti-knock protection, to prevent a load on the engine at lower RPM. If I would breath on the throttle with 87 gas it would want to downshift. This makes sense, but it also tells me the engine computer is sensing and adapting to E85. It also runs in V4 mode more often and longer on E85, another sign the engine adapts to E85. It is also injecting more fuel with E85 (as is expected with a flexfuel engine), so it must be measuring ethanol content.

 

I'm convinced the $100 E85 option is nothing more than the yellow gas cap and a way for GM to offer a choice. I wonder if there is some advantage to GM in CAFE or fuel economy calculations by having E85 as a customer option, versus a factory default. I see a very noticeable difference in smoothness and responsiveness on E85, and I like how it holds a gear longer. I think I'll try a couple tanks of 93 octane next then 89 octane, to see if there is any difference.

[Rawyzf]

There is more than a yellow gas cap. There is a sensor in the Fuel line. See my conversion thread.

 

http://www.gm-trucks.com/forums/topic/179602-tuned-and-converted-to-flex-fuel-2015-silverado-53l/

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Edited February 18, 2016 by Rawyzf

[6sigma]

I just read your thread on your E85 conversion, wow that is impressive! I did not know there is a separate fuel sensor (didn't see that documented in the parts diagrams I found). I may rethink running a lot of E85, although I gotta say it seems to run it just fine and the truck feels so much better I may do it anyway! It even shifts better. I wonder if it could be using the O2 sensors or some other way of measuring ethanol? My truck seems to be adjusting to E85 just as I have experienced and would expect from a FlexFuel engine. The injectors and fuel pumps are rated for higher flow, and the computer is commanding more fuel flow as it should.

[Rawyzf]

Did you put e85 in on empty? If not, you might have had enough regular to keep it sain.

 

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[6sigma]

Yeah, and I'm on the second tank. It is probably more like E60 here in the winter, but still makes me wonder how it is adjusting.

[POS VETT]

I have been running blended 93 & E85 (E85 in lower amount) on my '16 which is not a FFV. I have noticed that the engine runs better than running on straight 93, but I'm unsure if it ran as well as my '15 which was a FFV. I checked the undercarriage and there was no sensor for ethanol content; the electrical connector just sat there disconnected.

[joshc64311]

I used to run e85 in my last car. I ran it for 30,000 with no problems it was not ffv either. I bet the ECU has the ability to tune for e85 it will just take much longer without the sensor. My guess would be 2-3 tanks?

[diyer2]

To each their own. I think the difference between non FFV and a FFV may be more than known.

[Rawyzf]

Yeah, and I'm on the second tank. It is probably more like E60 here in the winter, but still makes me wonder how it is adjusting.

 

My last tank of e85 is reading 60% alcohol, so you are probably right with your guess.

[bigsapper]

:|

[redwngr]

Without the alcohol sensor (included with the E85 option) you won't get the horsepower and torque benefit of higher fuel rates in the programming tables for the E85. (and blends)

[chadder1313]

I would absolutely not run E85 in a non FFV. There has to be a tuning change for the vehicle to run properly and get the benefits of E85.

[Black02Silverado]

I've been running E85 in my 02 for a couple months now. No issues at all other than hard starts on cold morning as in when it is down to 29°F out. It runs smoother and seems to have more power.

 

One other benefit is my used oil analysis came back this last time looking way better than any of my previous UOA's. I also like the fact that E85 here is now $1.16 a gallon. Nice to fill up for under $30. Yeah, my mpg took a hit but when I calculate it out, the cost difference for E85 and 93 I'm still ahead running the corn juice.

[Willshire]

93 in a 6.2 i understand but why in a 5.3? unless it is tuned to run on it. A stock 5.3 requires no more than 89 (87 mfr recommended) at best so why the added expense of higher octane? Here 91 is roughly 50 cents more a gallon.

[davidio840]

So you are running E85 on a vehicle not suited to run on it?