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Author Topic: Why does my vin say my LT is flex fuel?  (Read 560 times)

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Jwh91

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Why does my vin say my LT is flex fuel?
« on: June 7, 2018, 21:41:50 PM »

"T" is the gas only and "Z" is flexfuel. My gas cap says DO NOT USE FLEX FUEL. But my vin is Z. So what's the deal? Is my 05 a Z71 with LT badges or what?
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EXT4ME

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Re: Why does my vin say my LT is flex fuel?
« Reply #1 on: June 8, 2018, 03:44:18 AM »

Gas cap has been changed?
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redheadedrod

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Re: Why does my vin say my LT is flex fuel?
« Reply #2 on: June 8, 2018, 06:30:15 AM »

Flex fuel gas caps are supposed to be Yellow as far as I know. Have you looked at the build codes to see what it says there? Also, if you are not the original owner it is possible the engine was replaced at one point with a non-flex fuel engine.

With Flex fuel there is supposed to be an extra sensor to detect the alcohol content and some other additional hardware to make it work as well. If that has been removed then you shouldn't be running E85.

With my GF's 2013 Silverado with 5.3 and Flex Fuel setup we found that the drop in Mileage was not worth the cost unless the fuel cost was at least $.40 cheaper to just break even. When a gas station near her work was selling E85 for $1 less per gallon she filled up there all the time but started getting tired of filling her 24 gallon tank all the time and when they increased their E85 to only $.50 less per gallon she decided it wasn't worth it. May be more worth it with the 32 gallon tanks the Avalanches have.

But again, if you are not the original owner you may want to insure the engine hasn't been changed and the flex fuel stuff removed if your vehicle was originally optioned with it.
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dna9656

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Re: Why does my vin say my LT is flex fuel?
« Reply #3 on: June 8, 2018, 21:42:53 PM »

How do we check to see if the engine has been changed? I have a Z in my VIN but I have a black gas cap.... More info, I have an 2006 LT model (I don't think that matters, flex fuel motors are not model specific (so far as I know) in the 1/2 ton models, maybe it's different for the 3/4 ton trucks...I have the RPO code L59 on the sticker.
« Last Edit: June 9, 2018, 10:36:54 AM by dna9656 »
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redheadedrod

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Re: Why does my vin say my LT is flex fuel?
« Reply #4 on: June 9, 2018, 07:24:06 AM »

First I would research the option codes to see if it is listed in your options. There are many option code look up services if you do a search. You may find your truck has some interesting options when you look for them.

If your VIN and your Option codes both state you have a 5.3 flex fuel engine then you likely do and they just changed the gas cap. The OP said his said NOT to use Flex Fuel in it so it is more likely the engine was changed for a non-Flex fuel engine.

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Vaeagleav

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Re: Why does my vin say my LT is flex fuel?
« Reply #5 on: June 9, 2018, 08:52:52 AM »

Look on your glove box for list of RPO codes and it should have a bunch of codes there.
Here is a link to an old thread listing the codes by model year and Flex fuel is L59 I believe for 2005 & 2006 first generation AVs :
http://www.chevyavalanchefanclub.com/cafcna/index.php?topic=84494.0

There is a different code for 2007+ AVs.
« Last Edit: June 9, 2018, 08:55:57 AM by Vaeagleav »
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Jwh91

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Re: Why does my vin say my LT is flex fuel?
« Reply #6 on: June 14, 2018, 07:34:22 AM »

black gas cap, sticker inside the fuel door saying do not use E85. Can I match any codes from my glovebox to a code on my engine? If so where?
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FishHawkAvy65

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Re: Why does my vin say my LT is flex fuel?
« Reply #7 on: June 28, 2018, 17:50:12 PM »

Did you look at the engine stamping yet? That would at least tell you if the block was changed, should match your VIN. Rear left hand side, I can't figure an easy way to see it......
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jmcclung11

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Re: Why does my vin say my LT is flex fuel?
« Reply #8 on: October 10, 2018, 07:21:35 AM »

My '05 has a black gas cap, but there is a sticker on the door that says E85 or Regular gas is ok.  The sticker is on the backside of the gas door.  I have used E85 in mine.
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dna9656

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Re: Why does my vin say my LT is flex fuel?
« Reply #9 on: November 24, 2018, 18:24:16 PM »

Flex fuel gas caps are supposed to be Yellow as far as I know. Have you looked at the build codes to see what it says there? Also, if you are not the original owner it is possible the engine was replaced at one point with a non-flex fuel engine.

With Flex fuel there is supposed to be an extra sensor to detect the alcohol content and some other additional hardware to make it work as well. If that has been removed then you shouldn't be running E85.

With my GF's 2013 Silverado with 5.3 and Flex Fuel setup we found that the drop in Mileage was not worth the cost unless the fuel cost was at least $.40 cheaper to just break even. When a gas station near her work was selling E85 for $1 less per gallon she filled up there all the time but started getting tired of filling her 24 gallon tank all the time and when they increased their E85 to only $.50 less per gallon she decided it wasn't worth it. May be more worth it with the 32 gallon tanks the Avalanches have.

But again, if you are not the original owner you may want to insure the engine hasn't been changed and the flex fuel stuff removed if your vehicle was originally optioned with it.
In 2006 MRFs STARTED to use only yellow fuel caps on FF vehicles. So, if the STARTED in '06 I suppose there is a chance you got a truck BEFORE they started.  My cap was black and I have a Z motor. On the fuel door is a sticker that I can use the 85% gas.
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2006 Chevy Avalanche,Z71, Upgraded to 4L65 E 2007 Standard 17" Chevy wheels but not the right year or style, new tires, exhaust, U joints, shocks, rear axle bearings and seals. New Driver's seat belt.  2007 Chrysler Sebring, 7  Yamaha motorcycles 6 Venture Royales 1 Road Star, 2 run, others for parts. 2 dachshunds, 1 house. 1 wife.
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