Tell The Truth

We've all seen gasoline commercials claiming to improve your vehicle's performance while cleaning internal engine components. From thought-provoking images of the ocean-that somehow connect fuel to our ecosystem- to the infamous talking cars that gleefully zoom back and forth after a fill up, we are bombarded with gasoline commercials. These commercials talk about the gasoline's quality, but never mention the additives or blends of detergents in their gasolines-kind of like Colonel Sanders and his secret chicken recipe. With gas prices skyrocketing in 2004, vehicle owners want the most bang for the buck in fuel quality when forced to pay a high premium.

I started testing fuels by collecting seven samples from popular California brands. Traveling from one station to another at 2 a.m., I collected samples of 91-octane gasoline while the attendants frightfully stared at me behind their bulletproof windows. Perhaps it was the wife beater and shaved head that set them off. Regardless, to keep the samples consistent we filled up early in the morning to lose as little volatility as possible, which translates into better octane and volatility control. Before collecting a sample, I put one gallon of fuel into my vehicle. This ensures the sample comes from the storage tank instead of the hose and maintains the integrity of the samples. I then filled and labeled each plastic 1-gallon container. After two hours of sample collecting, I was off to Rocket Brand Fuel Racing of Yorba Linda, Calif., to meet with Tim Wusz, a product engineer with over 20 years of fuel-testing experience. Let the test commence!

Ever wonder how fuel companies determine octane numbers?

Two laboratory octane numbers identify gasoline: the research octane number (RON) and the motor octane number (MON). The AKI octane-the one listed on the pump with the numbers in the yellow box-is the average of the research and motor numbers. The research octane number is always the higher number while the motor octane is lower. Generally speaking, the spread between the two numbers is about eight for 87-octane gasoline. (When you get to 91-octane it could be a 10-number spread.) To give you an example: A typical 87-octane gasoline could be comprised of 91-research octane and 83-motor octane. You average them to 87-octane. The 87-octane is considered a minimum octane reading, so all the oil companies blend to a couple of tenths over 87 to ensure the fuel being pumped into the vehicle is an 87-grade fuel. Gasoline companies call this a "giveaway." The same theory applies with an 89- or 91-octane. The 87-, 89-, and 91-octane you buy at local gasoline pumps are sold to meet government requirements for fuel economy and reduced emissions. These fuel grades are tailored for the daily driver, so they are a poor choice to power any high horsepower vehicle that flirts with high rpm.

Seasons change. So do the fuels. (Boiling gasoline at different temperatures.)

The changes in gasoline volatility are largely based on seasonal changes. These changes are controlled by the America Society for Testing and Materials (ASTM). During the summer time in California, all of the gasolines will have the same volatility. In the fall, the gases are still the same but the specifications change, so the fuel being sold is more volatile. The main changes in the distillation curve will be more noticeable as you get into the colder days of the winter season. The distillation change is more severe if you live in colder regions of the country. Gasolines are blended with hydrocarbons that produce a more volatile mixture to start engines easier when it's cold. When faced with zero degree weather a vehicle needs lighter elements to get the engine started. Distillation numbers are not as critical on fuel-injected engines as they are with carbureted engines.

The damaging effects of using leaded fuel

The octane readings of unleaded gasoline are capped at 100-octane. Higher-octane fuels contain lead. Tetra-ethyl lead (TEL) is one of the main ingredients added to fuel to boost octane. TEL is a very toxic material. Lead-based gasoline was eliminated from U.S. street mixtures on January 1, 1996 (January 1, 1992 in California.) The following year, cars were introduced with the first generation of catalytic converters. Before you attempt to pump your vehicle with some high-octane, leaded gas, take note that the lead content causes damage to a vehicle's catalytic converter and will slowly poison the oxygen sensors. Leaded gasolines still exist, but they marketed for sanctioned, off-highway events only.