Definitions

Specific Gravity

For liquids such as fuels, specific gravity is the weight of that liquid divided by the weight of water. Fuels are lighter than water, so the specific gravity of fuels is less than 1. Let’s look at an example. Turbo Blue 110 weighs 6.19 pounds per gallon and water weighs 8.33 pounds per gallon. Applying some math: 6.19 / 8.33 = 0.743. So Turbo Blue 110’s specific gravity is 0.743. If Fuel A has a lower specific gravity than Fuel B, Fuel A is said to be “lighter” than Fuel B. Literally, a gallon of Fuel A would weigh less than a gallon of Fuel B. Knowing a fuel’s specific gravity is important when it comes to fuel systems. Changes in specific gravity can affect how both carburetors and fuel injection systems meter fuel. When changing fuels, it is usually easier to switch to a fuel with a similar specific gravity.

Evaporation Points

The 10%, 50%, and 90% evaporation points indicate how much of the fuel evaporates at a given temperature. As an example, Turbo Blue 110 has a 10% evaporation point of 170 degrees F. This means that if you heat the fuel to 170 degrees, 10% of the fuel will evaporate. Higher 10% evaporation points are helpful in resisting heat effects including vapor lock. If we continue looking at Turbo Blue 110’s evaporation points, you’ll see that the 90% evaporation point is 228 degrees F. This is relatively low in comparison to common fuels like pump gas and is done to promote quick and clean combustion.

Please note: don’t try heating fuel at home. Evaporation points are measured per a specified test procedure in a laboratory where safety provisions already exist to deal with potential fire and other safety hazards. Heating fuel outside of a laboratory is not safe and must not be done.

Reid Vapor Pressure (RVP)

The Reid Vapor Pressure (RVP) of a fuel is the pressure exerted by the fuel vapors at 100 degrees F in a confined space. High RVP fuels tend to evaporate quicker than low RVP fuels. A high RVP can cause a fuel to evaporate too easily in the fuel system and increase the chance of vapor locking. If RVP is too low it might be hard to start the engine when cold. In racing applications, an RVP in the 5 to 6 psi range is typical, while some applications will prefer fuels with higher RVPs.

Octane

Octane rating is a measure of the anti-knock properties of fuel. The higher the octane, the stronger the resistance to engine knock. The terms preignition and detonation are often used in place of engine knock. While there are slight differences between these terms, think of them all as “uncontrolled combustion.” Such uncontrolled combustion can lead to loss of power, engine wear, and engine damage. Having enough octane is vital to keeping race engines going strong for as long as possible. There are two laboratory tests used to measure octane. The Research Octane Number (RON) test usually yields a higher octane number since it is easier on the fuel than the Motor Octane Number (MON) test. The average of the RON and MON tests is called the anti-knock index (AKI) and is usually labeled as (R+M)/2. In the United States pump gas is labeled with AKI values but other countries usually advertise the RON. We show you all the octane numbers for all of our fuels. Turbo Blue 110 has a RON of 115 and a MON of 105. The AKI of Turbo Blue 110 is the average – or midpoint – of those two numbers which is 110.