Flex fuel engines vs gasoline engine

Some Tundras are advertised as flex fuel 5.7 engines. Some are advertised as gas 5.7 engines. I am thinking about getting a 2019 or 2020 Tundra and I'm wondering what the engine differences are? I'm sure there are computer differences but what else is there? Will there be more trouble with the extra complexity of a flex as it gets older? I run 10% in all my gas stuff now, it does not seem to bother anything and it is cheaper. I probably will not change from that I doubt. Trouble free is what Tundras are famous for and that is what I want. thanks. Norm

 

I'm told that some of the inner components of the engine are "tougher" to be able to handle higher concentrations of ethanol.

I have an FFV and I can't say I can tell the difference, aside from the label that says I can use "flex fuel".

I never intend to use flex fuel. The only corn I'll put in my truck is the type people eat!!

 

So the flex fuel engines are ok, but there is an issue with some. It has plagued all years of flex-fuel trucks.

Ethanol percentage does not reset (this is a value that the computer calculates). It will continue rising, regardless of fuel type used. This causes hard start condition eventually, and the fuel pump will likely fail.

There have been a number of them discussed on this message board.

Once the no-start happens, the toyota TSB kicks in and you may get the pump replaced for free.

 

I don't think it will run at all on that

 

Thanks, that is exactly the some of the kinds of stuff I do not know about. I will search and find those threads to learn.

 

Yep, never heard of flex fuel. Flex Fuel is a term that defines the engine not the fuel. I asked the service manager on first oil change about the engine differences and he said it is just the fuel delivery parts. 80k on mine and no issues but don't run anything over E10. They don't even sell E85 in my area and when I travel to areas that do I resist the temptation to try it.

 

2013 5.7 FFV.

only difference I know of is recommended oil changes are 5K and not 10K but that’s only bc ethanol is considered to store contaminants more than regular gasoline so the oil needs changed more often.

IF you don’t use ethanol then I don’t think it matters but since I bought my truck new the dealership said my warranty was voided for not getting 5K oil change intervals. Same dealership also informed me my warranty was void for not getting all recommended services to include tire rotations lolololol.
I do oil changes at 10K bc I don’t use ethanol, I never have, and I don’t intend to. I bought FFV bc that’s what was on the lot in 2013.

We also have a Yukon XL and it’s a FFV.

the only bright side I see is IF we do experience a zombie apocalypse then I have 2 gas options where others have 1 gas option. Again, it’s a big “If”

 

Any flex fuel engine needs at a minimum two things....wide band O2 sensors and larger fuel injectors.

 

All of you folks with FFV. Use the obd reader to see what value the computer is calculating for ethanol percentage.

If its correct or close (0-20%), you’re probably ok.

If its higher and doesn’t reset to lower % after fillup and driving a few miles, your truck may have the no-start condition later that the tsb addresses.

 

The only visible difference in long term ownership I've seen so far is... You need a different Supercharger if you're going to go that route, you can't just bolt on the TRD one. Price is about the same though.

 

Even worse gas mileage.

 

I feel like for 2020 FFV was dropped.

 

I'm curious about this. Do you have anything to back up this statement? I seem to get pretty good mileage on my FFV.

 

Just an FYI....

Stoichiometric air-fuel ratio
Gasoline 14.7:1
Ethanol 9:1

If you burn pure ethanol, then your MPG will go down (1 - 9/14.7) or 39%. A flex fuel or non-flex fuel get the same mileage if they burn the same gas. When the flex fuel burns E85, it will see a MPG drop that's why you need bigger injectors and wide-band O2 sensors.

 

So worse gas mileage IF you run ethanol, identical if you don't. ‍♂️

 

Just comparing my truck to others with similar setups while doing mileage for work. Also, learning more about the FFV’s when they can have some hard start issues in the winter lead to other deep doves. Bouncing around the different forums has shown this general consensus. Never ran ethanol. Just 87 until winter comes, then 89.

Maybe it’s because mine is an older 2010…?

 

Why 89 in winter? You are paying extra for no gain.

 

Agreed - but some people “see” a difference- and it’s just personal preference.

Perhaps it’s belief that the boosted octane is less ethanol/better gas. Actually - the cheapest way to boost ratings is using good old corn alcohol - so in effect your getting slightly more ethanol buying the higher rated gas.

Ethanol has a higher vapor point - which is the main difference in winter blend fuels. Ethanol is also historically “cheaper” than the fossil fuel component in gas - which is part of why gas prices dip in winter (along with other factors like supply/demand).

Bottom line though - ethanol in an auto engine designed to run on the stuff isn’t “bad”. If your driving 10-15k miles a year and think your “saving” money buying premium or non ethanol fuel - your not. That 30 cents to $1+ a gallon you’ve spent would likely easily equal any additional repair cost after a couple of years - once you get out to 5 years or 15 years (reasonable life of any modern auto) - you’ve wasted probably 10-20% of the price of a new vehicle thinking your prolonging the life of your current car. But hey - I still buy powerball tickets thinking I “might” win - sometimes it’s just in our psychological makeup to do things that science proves aren’t logical.

 

In my area ethanol free is always 87 octane. When I had a Mercury Black Max with milled heads and running compression numbers in the 140s I added an octane booster when using ethanol free. They use ethanol to boost octane.

 

Rough starts. Significant drop in gas mileage, around 7-8 mpg when weeks prior averaged 12-14. Drop in power. Almost like it’s a different truck, especially towing. Usually happens once it drops below 50* outside.

I live in SE Va. not uncommon to have a freezing 30ish degree few days and then back to 70-80 degrees. Then the truck would act normal again. Gets frustrating.

Just switching over to 89, changes the truck’s characteristics back to “normal” for the most part.

Trying to figure out why my truck almost changed over night lead me to googling tundra FFV problems. After reading a ton of different threads a few others made the 89 recommendation after dealer reflashes (which didn’t seem to last long). And it seems to work best. Maybe the 89 burns hotter and keeps the truck in its sweet spot. I don’t know???

 

Gas stations use what they call "winter blend" fuel in our northern states, and this results in lower octane levels.

 

Oh I know. Just never experienced such a change when that happens when compared to all the other trucks, jeeps, 4Runners, I’ve had over the years until an FFV tundra.

it really showed after a routine hour and 45 minute drive I make. In warmer weathers, it’s a 1/4 tank trip. Once it’s cold, it’s damn near a half a tank, unless 89 is in it.

 

DFW also but even in cold weather before they switch over I notice a drop in MPGs. I think it is as much or more a cooler running engine then the gas.

 

I have the Bluedriver port reader but never use it.

Does anyone with a BlueDriver OBD2 port reader know what to check specifically to find this percentage?

 

I had the reset issue, my scan gauge would always show it 3-12% had my dealership just force it to 0 and remove that option. I have never ran ethanol. I no longer can run it but don't care I have never had an issue since. Scan gauge is alway at 0 and MPG's went up.

 

I've got an FFV and a buddy's guide friend has a truck with this problem, I'll remember this as I'll never run ethanol. Thanks!

 

How did you get them to do this? I’m having this problem now and they’re wanting to replace the fuel pump. I’m out of warranty though so I don’t qualify for the tsb.

 

I have a scan gauge II and I set one gauge to read ethanol % one day. I noticed that after filling up with 100% 93 octane it would go to 3,8,13% and mileage would go down. I took it in and showed the tech. He reset it. Then again the % would rise never go and stay a 0. He reset it again. The next time he said I qualified for the fuel pump replacement and that should fix it as well...it did not. I said can you just disable this I will never run Flex fuel. He did and it stayed at 0 from then on. It took him 30 seconds on tech stream.

 

Hmm, but there is 10% ethanol in basically all gasoline at the pumps nowadays, guess this is a flexfuel only issue?

 

I wonder how he did it. I have the Techstream software. Just need to know where to go to change the settings.