Flex Fuel

[Twithers]

I've got an '04 Tahoe that supposedly is Flex Fuel capable, but besides the VIN (1GNEC13Z74R146854) there is no other indication anywhere that it actually uses Flex Fuel.

Can anyone confirm, for sure, whether it is or not?

Are there any benefits to using Flex Fuel?

Thanks.

 

[Byoung1330]

Your 8th letter is z so yes it’s flex. Mine has it no where either but I have z in my vin. I’ve used it. Haven’t noticed no difference so I don’t even use it. If it was cheaper I would but it’s bout the same price here where I an

 

[gooffeyguy]

I know on newer models they came with yellow gas caps

 

[Myfirstz71]

My 07 and my 2011 both use it. Here in VA E85 is about .40 c cheaper per gallon. Reg88 is not quite “flex fuel” from my understanding and runs .20 cent cheaper.

I’ve used all three. I notice that my best gas mileage on E85 is 12-12.5 mpg. Reg88 only slightly better. But on basic unleaded gas I can get 14.5-15 mpg. Straight highway driving is obviously better, but these numbers are what I get daily driving to and from work.

 

[swathdiver]

I've got an '04 Tahoe that supposedly is Flex Fuel capable, but besides the VIN (1GNEC13Z74R146854) there is no other indication anywhere that it actually uses Flex Fuel.

Can anyone confirm, for sure, whether it is or not?

Are there any benefits to using Flex Fuel?

Thanks.

As long as the engine is original and someone didn't change, yes, that's an L59 motor.

Are there benefits to using it? Yes! It can be cost effective to burn it over gasoline if E85 is about sixty cents or more less per gallon. It runs cleaner through the engine, less build up of deposits, it actually cleans up the valves and pistons and the engines love it. The make more horsepower on it, switching over to a different set of tables.

You can also play around and mix fuels to get better gas mileage, somewhere between 15-25%, compared with straight gasoline.

Those L59s have an actual sensor that calculates the ethanol content. I don't think it will tell you though by a CEL if the sensor has failed and needs replacing, the code will be in there though. Maybe @Fless or @915_Tahoe can tell us for sure?

 

[Fless]

I've not seen any codes related to the FF sensor itself, but there could be a circuit code if the electrical component fails. If the sensor fails and you're running E85, it's probably going to run like crap since the fuel delivery isn't going to be right. Issues like that, I think, are more common with the later trucks that don't have the physical sensor, but use a virtual sensor.

 

[MassHoe04]

I posted this on another thread yesterday.
Some information on identifying Flex Fuel vehicles...

Decals can fall off or get destroyed...

This fact sheet from the state of MI was originally posted in 2006.
So, it is current up to 2007 model year... Maybe the additional information could save somebody from having to crawl under a tank.

https://www.michigan.gov/documents/How_to_Identify_Flexible_Fuel_Vehicles_161774_7.pdf

The first E85 model year listed on the sheet was the 2002 MY Chevy Tahoe/Suburban.

For Chevy Tahoe/Suburban...

The 8th VIN letter (or number) that is E85 compatible is shown as:
Letter Z for MY 2002-06
Number 3 or 0 for MY 2007

 

[tRidiot]

I believe the VIN Z Flex Fuel vehicles have a different intake and corresponding fuel pump. As for the fuel pump, the regular ones have 3 connections on top, the Flex Fuel has 2, I believe? Different electrical connectors, too.

Like this:

Regular GAS:






FLEX Fuel pump:

 

[Mudsport96]

Everything between the regular LM7 5.3 and the L59 5.3 on the engine ( except the injectors and fuel rail) are the same. The regular fuel engine has black plastic round rails, early L59s also had black plastic rails BUT they are a slightly different shape to accommodate the taller flex injectors so they cant be used on LM7 injectors ( edit regular fuel rails can be used with flex injectors but have to use spacers on the mounting holes to manifold) and the 06 and later flex engine has squared stailess rails.

Heads, pistons, cam, everything else is the same as far as ive ever been able to find. Which you would think that GM would bump the compression some to take advantage of the higher octane of the e85 and attempt to bring the mpg loss back some.

 

[Byoung1330]

I know on newer models they came with yellow gas caps

Yes I’ve seen that. Mine is a 04. It does not have the yellow cap but it’s flex