When the 1983-model cars hit the road next fall, add still another option to the list. Ford Motor Company will offer a propane-fueled Granada/Cougar to its line, the first time a major automaker has made a ''gas burner'' available as an original-equipment car option in the United States.
Up to now propane-conversion kits for cars - $1,000 and up - have been sold, especially to fleet users, as well as dual-fuel systems which burn either gasoline or propane. Some motor homes, for example, have dual-fuel systems on board. Too, Ford has been selling a factory-built propane option in the US since last April on all gasoline-fueled medium- and heavy-duty trucks and has been building propane truck engines for special orders since the mid-1960s.
Propane is a liquefied petroleum gas, often used as a fuel in lanterns and camp stoves, and is referred to as LPG.
To pave the way for the LPG cars in '83, Ford made the $900 option available in Canada in November and US fleet users can buy it in February.
Long used in stationary engines, farm tractors, and lift trucks in the US and Canada, in some countries - Italy, Belgium, the Netherlands, and Japan - up to 38 percent of all vehicles run on propane.
Ford sees an emerging market for the fuel in North America even though it only looks for about 10,000 sales a year. Some 350,000 conversions from gasoline to propane were done in 1981 alone, up from 75,000 in 1979.
''The advantages of propane are many,'' according to Stuart M. Frey, vice-president of car engineering for Ford, the biggest being its price at the pump - up to 50 cents a gallon below that of gas in many parts of the US. Too, it is clean-burning, does not call for the extensive emissions hardware of a gas-burning engine, engine wear is reduced, and the longevity of the exhaust system should rise.
And because the octane number is higher for propane than gasoline, ''we were able to raise the compression ratio from 9-to-1 on the gasoline-engine Granada to 10-to-1 with propane.''
What this means is better performance for the motorist. The 0-to-60 figure for an automatic-transmission car using propane is 3 seconds faster than a gasoline-engine car; and 2 seconds faster for a manual transmission.
Finally, supplies are plentiful, assures Mr. Frey.
On the negative side, however, LPG contains fewer B.t.u. than gasoline and thus mileage drops, but not by much. A propane-fueled Granada with a 2.3-liter, 4-cylinder engine will drop from the Environmental Protection Agency-rated 22 m.p.g. with gasoline to about 20 with propane.
With a 25-gallon fuel tank instead of the standard 16, Ford figures a range of 500 miles for a car burning LPG.
''While it is difficult for a casual observer to tell the difference between our propane cars and the gasoline-fueled versions,'' says Mr. Frey, ''the propane vehicles have better acceleration and improved cold-weather driveability.
''They also have the potential for longer spark-plug life; improved oil and oil-filter life; reduced cylinder, ring, and valve wear; require less carburetor maintenance, and should experience less exhaust-system deterioration.''
The propane used in automobiles vaporizes at normal atmospheric temperature and pressure. Thus, it must be stored under pressure to remain in a liquid state. Propane is sold by the gallon as are conventional fuels.
About 60 percent of the propane produced today is extracted from natural gas and 40 percent from refining crude oil.
Perhaps the biggest problem is finding a fuel pump. While there are some 5, 000 stations now selling LPG in the US, it could be even worse than trying to find diesel fuel in some parts of the country or unleaded fuel a few years ago before the US government required that all stations offer the fuel.
To help out the LPG customer, look for an LPG directory in the glovebox.