vp u4 fuel

[trx250-86]

As Jerry says

If you do not need race gas then yes you are wasting your money. If an engine needs 110 race fuel then yes there is a noticeable difference. You will ruin the piston is less than a day of use.

But what I'm asking is it worth it for the price?

[jamieg45]

Do you run u4 with the same compression you would with your race gas jamie?

I my self do not run the u4.4 vp I run vp c12, the uv is like adding nitris to your gas. It runs great like I said my buddy runs it in every dirt bike his daughter races. He started out using it in her kx 80 and then her big bore bike and now even in her new honda 150 4stroke as well. I will ask him this weekend of the ups and downs and if it's a big gain for you Johnny22.

[johnny22]

Cool thanks jamie. Thank you all for the replies

[F-Red]

I prefer to run a race gas since most gas stations carry an ethanol blend.

This is agruably, the best reason why you should use race fuel!

But what I'm asking is it worth it for the price?

YES! Worth every bit of the money. :encouragement:

[Jerry Hall]

But what I'm asking is it worth it for the price?

If your engine needs higher octane fuel than what you can buy at the pump to protect it from detonation, you have  two options.  Replace the piston daily or spend the money for higher octane fuel.

There are many options when it comes to spending money for higher octane fuel.  The options revolve around your engine build (what octane fuel your engine requires) and what your budget will allow to spend for fuel.

If your engine requires 110 octane fuel you need to spend the money and buy the race fuel of your choice.

If your engine requires less than 110 octane fuel you can mix race fuel with pump gas to arrive at a blend that has the octane your engine requires.


I read a lot of stories on the net about the fear of running fuel that has ethanol, MTBE and other additives that the refineries in your area add.  Any of these additives can affect the  jetting.  If your engine would run on pump gas without detonation, adding 15% ethanol or MTBE to your pump gas will require the fuel flow through the carburetor to be increased 5%.  A 5% increase in fuel flow would require one to increase the main jet 1 to 2 sizes, and richen the needle less than 1 clip position and less than on increment in the pilot jet size.  

I read a lot of stories on the net about guys telling everyone to run race fuel because it is consistent and is needed to keep your jetting consistent.  If you use the same brand and octane rating from the same fuel manufacturer, this statement is true, providing you are getting fuel from unopened cans or drums.  We are constantly repairing engines where customers bought fuel from a shop from a drum that was already opened and was said to be fresh, and undiluted.  The damage to the piston head and top of the cylinder indicates the fuel was not what it was advertised to be.


All gasoline whether it is pump gas or race gas has different heating values.  The heating value primarily determines what size jet must be used to provide optimum power.  I see as much as a 2 to 3 main jet sizes difference in the optimum main jet sizes needed from different brands of racing gas of the same octane rating.

In summary:

1. Use fuel that is at least 2 to 3 octane points higher than what your engine requires.

2  Optimize your jetting on the fuel that will ALWAYS be available.

3. Do not change from one brand to another or one octane level to another unless you are prepared to go through the re-jetting process.