Gasoline and Lubricants

Gasoline and Grease

Engine fuel is mainly made up of hydrogen and carbon, mixed so that it will burn with oxygen present, and will free its heat energy into mechanical energy. Liquid fuels are ideal for internal combustion engines, because they can be economically produced, have a high heat value per pound, an ideal rate of burning, and can be easily handled and stored. The most common engine fuels are gasoline, kerosene and Diesel fuel oil.


Gasoline has many advantages and is used to a greater extent than any other fuel in internal combustion engines having spark ignition. It has a better burning rate than other fuels, and, because it vaporizes easily, it gives quick starting in cold weather, smooth acceleration and maximum power.

High performance cars require high performance gasoline. Owners of pre-1971 cars know that their cars require leaded gasoline to run correctly. As leaded gasoline is not sold in the United States, these owners need to buy Lead Substitute Additives (generally $1-$2 per bottle) which are good for one tank of gas. The lead is important because it acts as a lubricant for the internal engine parts and stops them from wearing out to quickly. Engines built in 1971 and later are generally built to run on Unleaded Gas so adding Lead Substitute won’t help. In fact, lead damages Catalytic Converters (mandatory on cars built after 1977), and is more harmful to the environment, so don’t add it if you don’t have to. In either case, you should be purchasing the highest Octane gas at the pump. Supreme Unleaded (92 Octane) is fine and should be used for most engines and everyday driving. Owners of truly high performance engines (i.e. Compression ratios greater than 10.0:1) should consider using Octane boosters to keep their engines running smoothly. Octane boosters may also help if you plan to race your car extensively or whenever you want a little more power. Note that Racing Fuel (104 Octane +) is expensive (often more than triple the price of Supreme Unleaded) and hard to find, and should only be used if you truly have an engine built for racing. It is just overkill in a regular street car being taken to the drag strip and won’t give you any measurable improvement over Supreme Unleaded.

Diesel Fuel

Diesel fuel oil ranks next to gasoline in quantity used. It can be produced as cheaply as gasoline, but its use is limited to Diesel type engines. The use of kerosene as a fuel is usually limited to farm tractors, marine and stationary engines, all which operate at a fairly constant speed. Its traits are such that it cannot be properly mixed with air and controlled in variable speed engines.

Octane Rating

A gasoline’s ability to resist detonation is called its “octane” or anti-knock rating. Gasoline from asphaltic base crude oil produces less knock than one from paraffinic base crude. Cracked gas has less tendency to knock than straight run gas. All marketed gasolines are a blend of straight run and cracked gasolines, so unless their blending is controlled, the anti-knock qualities will vary.

A mixture of iso-octane, which has a very high anti-knock rating, and heptane, which makes a pronounced knock, is used as a reference fuel to establish an anti-knock standard. The anti-knock value or octane number is represented by the percentage of volume of iso-octane that must be mixed with normal heptane in order to duplicate the knocking of the gasoline which is being tested. These ratings range from 50 in third grade gasolines to 110 in aviational fuels. The rating of 100 means a fuel having an anti-knock value equal to that of iso-octane. If the octane rating of a gasoline is naturally low, the fuel will detonate as it burns and power will be applied to the pistons in hammer-like blows. The ideal power is that which pushes steadily on the pistons, rather than hammer against them. The octane rating of a gasoline can be raised by treating it with a chemical which is not a fuel. The best chemical known is tetra-ethyl lead compound, which is added to the gasoline.

Tetra-ethyl lead is a liquid which mixes thoroughly with gasoline and vaporizes completely. Ethylene dibromide prevents the tetra-ethyl lead from forming lead oxide deposits on spark plugs and on valve seats and stems. Red dye is added to identify an ethyl treated gasoline and to warn against its being used as anything but an engine fuel. In 1975, it became illegal to use a leaded gasoline except in cars built prior to this time. With the addition of the catalytic converter, it is undesirable to burn leaded fuel, because leaded fuel will clog the converter and increase the back-pressure of the exhaust.

Cetane Rating (Ether)

The delay between the time the fuel is injected into the cylinder and ignition is expressed as a cetane number. Usually, this is between 30 and 60. Fuels that ignite rapidly have high cetane ratings, while slow-to-ignite fuels have lower cetane ratings. A fuel with a better ignition quality would help combustion more than a lower cetane fuel during starting and idling conditions when compression temperatures are cooler. Ether, with a very high cetane rating of 85-96, is often used for starting diesel engines in cold weather. The lower the temperature of the surrounding air, the greater the need for fuel that will ignite rapidly. When the cetane number is too low, it may cause difficult starting, engine knock, and puffs of white exhaust smoke, especially during engine warm-up and light load operation. If these conditions continue, harmful engine deposits will accumulate in the combustion chamber.

Pressurized cans of starter fluid are available in emergencies, but are not desirable, because they tend to dry out the cylinders, and are dangerous if used improperly. There are also liquid forms of starter fluid available which can be added to the gasoline.

Fuel Additives

Tetraethyl lead was used in some gasolines to reduce or prevent knocking. However, in 1975, it became illegal to use leaded gasoline except in cars built prior to this time. Methyl Tertiary Butyl Ether (MTBE) is used in unleaded fuel to increase the octane. Gasoline exposed to heat and air oxidizes and leaves a gummy film. Detergents are now added to gasoline to prevent this. The detergents keep the carburetor passages and fuel injectors free from deposits, which could cause hard starting and problems in driving. Deposits also restrict the flow of fuel and cause a rough idle, hesitation of acceleration, surging, stalling, and lack of power.

Alcohol is frequently used as an additive to commercial gasoline, because it will absorb any condensed moisture which may collect in the fuel system. Water will not pass through the filters in the fuel line, so, when any water collects, it will prevent the free passage of fuel. It also tends to attack and corrode the zinc die castings of which many carburetors and fuel pumps are made. This corrosion will not only destroy parts, but also clog the system and prevent the flow of fuel. By using alcohol in gasoline, any water present will be absorbed and pass through the fuel filter and carburetor jets into the combustion chamber. Alcohol additives are often purchased and added separately into the gas tank to prevent gas-line freeze and vapor lock.

Alcohol as a Fuel

The increasing cost of gasoline, and the new laws requiring alternative fuels have turned the attention of car and truck designers to substitutes. Chief among alternative fuels is alcohol. Considerable research has been done, and is still carried out, for alcohol in spark ignition engines. Alcohol fuels were used extensively in Germany during WWII, and alcohol blends are used in many vehicles at the present time.

Methanol and ethanol are the forms of alcohol receiving the most attention. Both are made from non-petroleum products. Methanol can be produced from coal, and ethanol can be made from farm products such as sugar cane, corn, and potatoes. Both alcohols have a higher octane number than gasoline. High heat of vaporization, however, indicates that the use of alcohol could give harder starting problems than gasoline, which means a need for a larger fuel tank and larger jet sizes in the carburetor. It requires less air for combustion, though, which compensates for the high calorific values. In proportion, this could result in practically the same air-fuel ratio for all three.

Experimental tests have shown that alcohol-fueled spark ignition engines can produce as much or slightly higher power than gasoline. Alcohol fuels have a higher self-ignition temperature than gasoline, which rates them better from a safety standpoint, but this same quality bars them from use in a diesel engine which depends on the heat of compression to ignite the fuel. At the present time, only ethanol can be blended in small concentrations (10%%) with gasoline. Because of the high octane rating, alcohols can be used in relatively high compression ratios, and experiments indicate that emissions from engines fueled by alcohol would require the use of exhaust gas recirculation controls.

Synthetic Grease

Synthetic lubricants are available for transmission (auto and manual), and for rear axle assemblies. They may provide some advantages in lubrication, but at a very expensive price. We are a bit wary of the effect on the operation of friction components, such as the clutches in auto transmissions and limited slip differentials, so have not tried them. We also doubt that measurable differences in performance would be found with our relatively heavy vehicles.

We have noted the advertising of some probable fact and then inferring that improved performance will result. In the case of the synthetic wheel bearing grease, the drag caused by properly adjusted and lubricated wheel bearings on a 4000# vehicle is such a minuscule amount, an improvement of 100% of the drag would still be un-measurable. In fact, the bearings could probably be run without any grease, and the vehicle would run about the same until the bearing seized. When evaluating such advertising, consider the power producing or power consuming effect of any engine or running gear component or material. If it is responsible for a relatively minor proportion of the total power output, even significant percentage improvements of that item would still be almost undetectable!

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