Identifying Flex Fuel Vehicles
Technician training

Here are some great tips about how to identify a flex fuel vehicle so you can select the right pump for your vehicle. Flex fuel vehicles can run on either gasoline or alcohol-based fuels like E85. The challenge is that it’s possible for the same year, make and model vehicle to use different fuel and engine management systems. 

Unique Parts

First, let’s talk about why flex fuel vehicles require parts designed just for them, and why you don’t want to use E85 in any vehicle that isn’t designed to run on alcohol-based fuels. E85 is eighty five percent ethyl alcohol, with fifteen percent gasoline added to it to make ethanol. So compared to gasoline, E85 has a higher oxygen content, more electrical conductivity, and it absorbs more moisture. That makes it highly corrosive. So if your vehicle isn’t designed to use E85, DON’T PUT IT IN THE TANK! E85 also yields less energy. So a flex fuel vehicle must have the right software in order to adjust its air – fuel ratio and generate the necessary power.

Determining if a vehicle is flex fue

One of the easiest ways to determine if a vehicle is flex fuel is to look at the gas cap. On a flex fuel vehicle, it’s yellow, and printed with the fuels that can be used.  A label on the inside of the fuel door will also indicate the fuel type. You can also check for Flex Fuel or E85 badging on the vehicle, or take a look at the eighth character of the VIN. Refer to service or application information that will tell you whether the vehicle is a flex fuel application.

Only use E85

It’s important to make sure you’re only using E85 in a flex fuel vehicle. In a conventional fuel system, it can cause a lot of problems.


  •     High alcohol content causes steel lines to corrode. That’s why the fuel lines in flex fuel vehicles are usually lined with nylon.
  •     Conventional rubber connecting hoses and O-ring seals tend to dry out when exposed to E85. That can lead to fuel leaks.
  •     Metals in the fuel pump will corrode. That means poor pump performance. Conventional fuel pumps typically last for about nine thousand hours. But put one in a flex fuel vehicle, and it may only work for about five hundred hours
  •     E85 will also deteriorate a conventional fuel level sensor and float, causing it to malfunction.

To make the right repair, you have to properly identify flex fuel vehicles and use the parts that are made for them. With these tips, you’ll be well on your way.