Having a difficult time deciding which octane you should select for your tune. We will cover the basics on what is needed for each application, and which fuel you should run in each situation.

Flex Fuel has been a very popular option amongst N/A vehicle. From the coyote 5.0 or the gen 3

Hemi 6.4. Flex fuel will give you the ability to run any octane and will auto adjust as some call it.

The ability to run Flex fuel on newer vehicles right out the factory has been easier, some older

vehicles will need to have the fuel pump & or injectors upgraded in order to run Flex or straight

E85 fuel. Due the nature of the fuel, E85 you need 30% more fuel then regular pump 91/93

octane. Running Flex fuel also has its advantages and disadvantages. Many advantages are

power and cheaper fuel at the pump, however due to needing 30% more fuel, your fuel efficiency

will drop. The ability to add in any fuel at a fill up also makes running super easy and convent.

However, what all is needed when you do change octane. We have a few steps that in which

you should follow to have the vehicle learn the new fuel content, so you won't have any negative

effects.

1. If you are going to change fuel, make sure to be 1/4 to 1/2 tank.. Filling up with small amounts

of different fuel will make the process longer.

2. Make sure when filing up your vehicle your engine is shut off. Most of the time the vehicle

running will not trigger the Flex fuel logic to start adjusting.

3. Make sure you drive the vehicle for an adequate time after refilling. You'll want to drive the

vehicle on average 10/12 miles for the vehicle to start adjusting. During this time frame you may

experience slightly rougher idle, fluctuation in idle rpm or even throttle response. While the vehicle

is learning you can see the process by looking at your AFR gauge on dash/menu to see the AFR

changing. While running 91/93 octane your AFR gauge will be around the 14.7 however with E85

AFR is around 9.8. Depending on your ethanol content you'll be able to see the gauge move

depending on the content.

Another benefit would be to install an Advanced Fuel Dynamics Flex link kit on your vehicle. The Flex

link kit will make it easy for you know the quality of fuel that you are getting from the pump without

having to manually check the E-content with a glass beaker.

A recommendation that is almost always necessary when running E85 or Flex is to change spark

plugs.  We recommend One Step Colder and gapped tighter.  Usually .028 works well with any

forced induction.  These plugs will work fine on turbocharged, supercharged, or NA applications.

For boosted Hemi/Hellcat applications, we recommend NGK2309 known as LFR7AIX.

For boosted Coyote, we recommend NGK6510 known as LTR7IX-11.