Fuel and Additives

Can Someone Tell Me About Gasoline?

[AWN] You DO all know that all the gas companies fill their tanker trucks from the same refineries, and that the only difference between one brand and another is the additive package… Right? Ok. With that out of the way…

Chevron’s "Techron" additive and Texaco’s "System 3" additive are basically the same thing: They’re detergent packages that help to keep deposits from forming on the backs of your intake valves and in your fuel-injectors, etc.

However… There’s not enough detergent in EITHER brand (or any of  the others) to keep your valves PERFECTLY clean, so if you care about  that sort of thing, you should periodically run a bottle of  valve/injector cleaner through your fuel system.

Any Chevron station will sell you a bottle of Techron; it’s pretty cheap and is recommended (by name) by Porsche, BMW, and maybe a couple other manufacturers.

Personally, I prefer Redline SI-1 or SI-2 (same stuff, different bottle sizes). It costs just about the same, but may be harder to find.

The recommended dosage for prophylactic purposes is one bottle every few thousand miles. For curative purposes — like if your car’s running poorly and you suspect clogged injectors — the dosage is two bottles in a tankful of gas followed by one bottle in each of the next two tankfuls.

Be aware, if you’ve never poured a bottle of Techron or SI-1 into your tank before, that it may loosen deposits that have formed in the system ahead of the fuel filter. Those deposits will break free and be captured by the filter, potentially clogging it and necessitating its replacement.

I use only Unocal gasoline in my cars, mostly because my local Unocal station has newer underground tanks than all the other stations in my area AND I know when they fill the tanks.

[REM] My cousin drives gasoline tanker trucks for a living. All brands of gasoline get their gas from the same refineries.

 The only difference in an 8000 gallon load is the 1 QUART can of additives they dump in  separately!

What Does "High Octane" Mean?

[AWN] Higher-octane fuel isn’t harder to ignite in the usual way (that is, with a spark); the octane rating just indicates how easily the fuel can SPONTANEOUSLY ignite before the flame-front reaches it. "Spontaneous pre-ignition" is just another phrase for "detonation" or "knock"; higher-octane fuels resist knocking better than low-octane fuels.

[EN] There are two types of octane numbers for gasoline, the Motor Octane Number (MON) and the Research Octane Number (RON).  The ASTM methods for MON and RON use the same test engine, but operate under different

 conditions. MON is a measure of performance of the fuel at high speeds or under heavy  loads, while RON repersents the performance during low speed conditions. The octane number  displayed at the pump is the average of these two values ([R+M]/2).

Which Fuel Additives Are Recommended?

[Merritt Wikle, Auto Enthusiast & Chevron Lubricants Employee – 2000/10/20] The formulations of all manufacturers aftermarket products is very proprietary. So it is unlikely anyone knows Chevron or BG’s formulations. Chevron sometimes tests/analyzes selected products a part of competitive analysis. I do know BG44K is a fine product. Further, Techron Concentrate is not just "4% active ingredient", with "filler" for the balance. [BTW filler in gas additives is typically some type of solvent.]

The active ingredient in Techron Concentrate is engineered and manufactured by Chevron. Though we do contract the actual bottling of the "juice" to others; it is Chevron that originally invented, made, and patented PEA (polyetheramine) fuel additive technology in the 80’s.

In short, Techron Concentrate is the "original", and still unbeatable fuel system treatment.

In fact, the automakers use Chevron gasoline with Techron for EPA testing, even though we do not market gasolines in the Midwest (they haul from Louisville KY).

While I cannot comment on any specific Chevron Chemical customers I might know of (I’m not in Chevron Chemical group), Chevron Oronite Chemical Division sells very good PEA fuel system additives (not Techron Concentrate, though) to many well-known customers both as aftermarket chemicals, and for use in bulk gasolines. Typically these customers package and market these chemicals, or use them in bulk gasoline.

[GM] BEWARE! The 44K can is perhaps the worst designed product on the market. A large opening means much will spill down the side of your NSX. At $15 a can you are wasting part of the product, but worse it left marks in my paint!  I had to polish the area several times to remove them, then re-wax of course. Luckily I was minutes from home when this happened. I don’t know if it gets worse if left on the paint for longer times.

What Are The Specs On Gasoline?

[BZ] Gasoline: Mobil Super+ unleaded, 92 octane (min). Color: yellow-green. Gasoline Density: 0.75 grams/mL. Air Temp: 16 to 18 deg C. Date of test: January 1992. 1 gallon

3.785 liters

3785 mL

2838.75 grams

6.25 pounds.

Petroleum Proof, High-Performance Gasolines

Popular Hot Rodding Magazine, January 1998

 By Scott Parkhurst 

Octane is a measurement of a fuel’s resistance to ignition. Ideally, the air/fuel mixture will ignite at the proper time and burn smoothly through the power stroke. The idea is that one powerful combustion of the air/fuel mixture is better than several randomly-ignited small flame fronts. When you can precisely control the point at which the fuel will ignite, maximum performance of the engine can be achieved, and power-robbing knock and ping will be eliminated. Knock and ping are a result of abnormal ignition, or multiple flame fronts colliding within the combustion chamber during the compression stroke.

All reputable fuel manufacturers determine the octane rating of their gasoline in the research lab using a special, dedicated single cylinder engine. Comparing the gasoline to a series of standard reference fuels in the test engine results in either a research octane number (RON) or a motor octane number (MON) depending on a set of operating conditions. The RON is determined with the test engine operating at 600 rpm, at standard barometric pressure, and the intake air temperature set at 125 degrees Fahrenheit. RON is primarily used to address part-throttle knock and ping problems. The MON addresses wide open throttle operation and is determined with the test engine spinning at 900 rpm, also at standard barometric pressure, and the intake air temperature pumped up to 300 degrees.

The best predictor of a fuel’s performance in a street/strip machine is the Anti-Knock index (AKI). This is simply the average of the RON and MON numbers, or (RON + MON) / 2. Most all octane ratings posted at the pumps are determined by this AKI formula, and are the minimum values you could expect to see. The minimum octane requirement

 of your engine is determined by several variables besides the compression ratio. The  engine and cylinder head configuration, air/fuel mixture, timing, coolant temperature,  atmospheric pressure, relative humidity, and ambient air temperature will also affect the  octane required to make your mill produce maximum power. 

The burn rate of a fuel is a measurement of the time required for complete combustion of the air/fuel mixture. The notion that octane ratings affect the burn rate of fuel is about 180-degrees from reality; burn rate is a function of several variables, and the two are completely independent, although there is generally a correlation between octane ratings and burn rates.

To give you a good example of this, we contacted Jim Wurth from Sunoco Race Fuels. He explains, "A perfect example is Sunoco Maximal, which is our fastest burning fuel, and coincidentally one of Sunoco’s highest octane fuels at 116 (R+M) / 2. A lot of Pro Stock teams rely on Maximal for those sub-seven second runs. When they are turning 9,000 rpm or more, the fuel has to burn pretty quickly to achieve complete combustion".

Octane boosters offer little help in the quest for higher octane. Most popular street-legal octane boosters claim increases in octane ratings up to five points, and those boosters intended for off-road use only claim up to seven points. That’s a lot of octane to hope for simply by pouring an additive in a tank. Sunoco told us that before they launched their GT-100 Unleaded retail pilot program, they wanted to be sure that a 100 (R+M) / 2 octane street legal fuel would be of value, and that enthusiasts would not be able to get the same (or better) results using an octane booster. Nine of the most popular retail octane boosters were put through a series of tests to determine where the consumer could get the most bang for the buck. The test results were verified by an independent testing facility, using several brands of regular unleaded and premium gasolines, just to make sure everything was legit.

According to Mark Borosky, Vehicle Test Engineer for Sunoco,"Of the nine octane boosters tested, none showed a significant increase, and one actually lowered the octane number of the test gasolines."Testing repeatedly showed a maximum increase in octane of 3.5 points by only two of the six street legal octane boosters when the recommended treatment rate was blended with lower base 87 octane gasoline. The best the remaining four products could muster was less than a one point increase. "While clearly no one would actually use an octane booster in a low base octane fuel, we wanted to give the manufacturers the benefit of the doubt relative to their claims of five-to-seven point increases," explained Borosky.

When tests were performed using 93 and 94 octane fuel, even the two best products from the previous tests produced a disappointing 1.5 to 2 point maximum increase. The remaining four street-legal octane boosters showed less than a .5 point increase. Those products designated for offroad use only didn’t fare any better than the street-legal products. Subsequent tests where the dosage of octane booster was doubled, tripled, and even quadrupled produced only minimal improvements in octane, regardless of the base octane number of the test gas. In fact, quadrupling the treatment rate of the most powerful additive produced only a 3.5 point increase in octane when added to 93 premium, resulting in a cost of $3.25 a gallon.

An alternative path to octane euphoria is to blend gasolines of different octane levels yourself. It’s easier than you may think, safe, and the results are predictable. The formula for mixing gasolines of the same type is pretty straightforward. When you mix a 50/50 blend of two unleaded fuels, simply average the two octane ratings to determine what’s in the tank If you mix 94 and 100, you get 97. The same generally holds true for leaded gasolines, assuming the lead content is

 nearly equal.

Blending a leaded fuel with unleaded, however, pushes the octane up a bit more than the math would suggest, due to the effect of the lead. Just a gram or two of lead blended into the unleaded fuel will raise the octane number significantly. Commercial leaded racing fuels contain anywhere from a trace to six grams of lead per gallon. If you were to mix 50 percent 110 octane leaded fuel with 100 octane unleaded, you would actually end up with an octane number around 106 to 107. Keep in mind that even the smallest amount of lead or leaded gas line with unleaded, could spell the end of your catalytic converter or oxygen sensor. The same holds true for using octane boosters intended for off-road use only. A word to the wise, check for any lead content in all the additives you might mix with your unleaded gasoline. And check with your state emissions regulations for street use.

We asked Sunoco’s Wurth about using aviation fuel in an automobile engine. He was emphatic when he said, "Don’t do it. Even though Sunoco is a major producer of aviation fuel, this fuel is specifically blended for aircraft engines. Aircraft operate under very different conditions than automobiles, and the fuel requirements are quite different as well. Aircraft engines generally…. run within a very narrow rpm range. There’s no need for transient throttle response in an airplane because after the pilot does the initial engine run-up, the throttle is set in one position and the rpm doesn’t normally change until landing. Also, airplanes fly where the air is cold and thin, and the atmospheric pressure is low. These are not even close to the conditions your street machine will see on the ground. Also, since most piston-driven aircraft cruise at 3,000 rpm or so, the burn rate of aviation gas is much too slow for any high performance automotive applications."

What is it that makes race gas so different? What’s it made of? Sunoco tells us their GT PLUS 104 octane unleaded race gas is only 15-20 percent traditional gasoline, and about 85 percent additives! Actually there are about 120 different chemicals in GT PLUS. One reason it isn’t street legal is the high oxygen content. The EPA requires that the oxygen content of a street legal fuel cannot exceed 2.9 percent. GT PLUS is about 3.5 percent oxygen. This fuel is light in weight at only 6.14 lbs-per-gallon. The high oxygen content improves the octane, and when the induction system is properly calibrated, this fuel will help make additional horsepower. The high oxygen content has a supercharging effect, since 3.5 percent oxygen is the equivalent to about 17 percent more air. Different fuels can actually alter horsepower 5-to-10 percent or more.

We wanted to to know more about the different types of race gas Sunoco had, and didn’t realize there were five different types of racing fuel alone.

GT-100 Unleaded, is a clear fuel with a pump octane of 100, and will handle compression ratios of up to 12:1, and is street legal in all 50 states.

GT PLUS, is also unleaded, and is rated at 104 octane. It is suitable for compression ratios up to 14:1 and is colored light blue. It will not harm oxygen sensors or knock sensors in computer controlled engines. It is not street legal.

STANDARD, is a leaded fuel rated at 110 octane, is colored purple, and is intended for drag racing, road racing, and race boats.

SUPREME, is also a leaded fuel and is dark blue. It was developed to help resist vapor lock and meet the demands of sportsman, modifieds, offshore powerboats, and endurance racing where engines regularly run in excess of 7000 rpm.

MAXIMAL, we mentioned earlier, is colored red, has 116 octane, and is leaded. It is intended for exceptionally high performance applications like Pro Stock where extremely high cylinder pressures are common. Its extremely fast burn rate is satisfactory where rpm exceeds 10,000.

Now that you’re an expert on gasolines, you probably would like to know where to buy and store the stuff. If you are fortunate enough to live in the mid-Atlantic states, you can take advantage of Sunoco’s GT-100 Unleaded retail pilot program and get 100 octane race fuel at pumps located at select Sunoco stations. The rest of us have to purchase from local speed shops, at race tracks, or directly from Sunoco distributors.

When you plan on buying fuel in quantity, say a 55-gallon drum, you’ll be happy to know that racing fuel has a shelf life of about a year, if you store it properly. The container must conform to all safety standards, and should be made from metal or polymer. Make sure the container is opaque and solid in color. The white plastic jugs we see at the track should be used for short-term storage only. They let in sunlight, which will affect the fuel. The lead in leaded fuel and other chemicals in unleaded fuel are photosensitive, and will dissipate if they am exposed to the sun. Keep any container tightly sealed to prevent evaporation.