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Research octane ratings do not adequately define the antiknock performance of gasolines in cars on the road; gasoline sensitivity, composition, and other fuel properties also have effects. Specific correlation equations can express the effects of the fuel properties, but a different equation is needed for each car and speed. With the aid of simple statistics, the different equations can be combined to yield the Customers' Antiknock Rating, or CAR. The CAR of a gasoline is uniquely related to the percentage of cars the gasoline will power without knocking; even in simplified form, CAR is much better than Research rating. The use of CAR improves comparisons of gasolines, quality control, evaluations of processes, and projections of future antiknock quality. Although the CAR is more complex than Research rating, it has many advantages; we are using it and hope the automotive and petroleum industries will consider adopting something like it in the future.

The amount of vapors lost from an automobile fuel system is determined from changes in density of the gasoline as it weathers. The composition of the vapors lost is calculated from the initial composition of the fuel by simple distillation theory. The techniques are simple, precise, and generally applicable.

The infrared radiation method of compression and end-gas temperature measurement was applied to the problem of measuring gas temperatures up to the time of knock. Pressure data were taken for each run on a CFR engine with mixtures of isooctane and n-heptane under both knocking and nonknocking conditions. Main engine parameters studied were the intake pressure, intake temperature, and engine speed. The rate and extent of chemical energy release were calculated from the temperature and pressure histories using an energy balance. The computed rates of chemical energy release were correlated to a chain-type kinetic model

Automotive steam propulsion systems would have modest fuel quality requirements, but they would probably consume 50% more fuel than conventional gasoline engines giving the same vehicle performance. Lubricant needs of steam systems are still poorly defined, but they would include good rust protection, demulsibility and stability. The petroleum industry could meet these fuel requirements with little new technology, but substantial increase in capital would be needed for expanded refining, exploration, production and transportation facilities. Meeting lubricant needs would require a technical development program. Nevertheless, if steam-powered vehicles appear in significant numbers, commercial fuels and lubricants will be available for them.

Future U.S. demand for motor fuel used by passenger cars and light trucks will be met with unleaded gasoline and automotive diesel fuel. Long term, new raw materials -shale oils, tar sands and coal liquids, or methanol - may become available but, at least to the year 2000, conventional crude oil will predominate. If crude oil supply is not interrupted, the U.S. refining industry will be able to meet expected motor fuel demand with processing technology available now, and largely with facilities already installed. However, proper matching of future vehicles and fuels can significantly increase the efficiency with which crude oil is utilized. The refinery gasoline pool should be proportional among at least two octane grades, but gasoline-powered vehicles should be designed to a single octane target near the economic optimum of about 89 (Research + Motor)/2 octane number to achieve maximum vehicle-miles per barrel of crude oil.

Until 1970, emission standards and car modifications needed to comply with state regulations had relatively little effect on gasoline quality. Then in 1970, Ford and GMC announced that all or nearly all their 1970 and later model cars would be designed to operate on unleaded gasoline of 91 Research octane number. This paper covers the production capabilities of the petroleum industry, the effect of leaded gasoline on emissions, consumer advantages and disadvantages of unleaded gasoline, gasoline volatility, and future gasoline quality.

Current evidence indicates that cars manufactured after 1974 or 1975 will be required to operate on unleaded gasoline. To determine the level of octane quality justified when refineries are producing only unleaded gasoline, improvements in mileage attainable by using gasoline of higher octane number were compared to costs of raising octane number. Motorists' total gasoline costs per mile are lowest when the octane number of the unleaded gasoline pool is in the range of 85 to 87 Motor octane number. And, dividing the unleaded pool into at least two octane grades -- one at 1 or 2 units above and one at 2 or 3 units below the pool value -- maximizes car satisfaction for any given pool quality.