Rank has its privilege. Thus perhaps the stately Rolls-Royce really should not be expected to conform to the fuel economy standards that apply to more common automobiles. But the bowing and scraping that has accompanied the federal government's special treatment of the Rolls is something that deserves recognition.

Take the most recent episode as described in the Oct. 9 Federal Register (page 67108). The National Highway Traffic Safety Administration published its proposed decision to grant Rolls-Royce an exemption from the fuel economy standards. To put it bluntly, the various Rolls-Royce models, including the Bentley, get about half the mileage required under current regulations. And under the law, autos that don't meet those standards cannot be sold in this country unless they have a specific exemption.

Normally, an automaker goes to the NHTSA seeking an exemption three years before the model year of the car it plans to market. The exemption now being sought for Rolls-Royce covers the model years 1979 and 1980 -- cars that for the most part already have been sold.

It's the justification for the exemption for those sold cars that contains the most interesting information. For example, before doing something for a petitioning automaker such as Rolls-Royce, NHTSA must see if the offending car could get better gas mileage by cutting down on its size. The interior volume of the Rolls-Royce is 100.4 cubic feet. According to the government standards that establish gas mileage levels, that volume "places the [Rolls-Royce] line in the 'compact class.'"

Well, you can't demand that a car cut down its size if it's already a "compact." But what about getting it to use a more economical engine? Study by NHTSA found, however, that the Rolls-Royce cars "are not overpowered" when compared to American luxury cars such as the Cadillac Coupe de Ville and Lincoln Continental.

The Rolls-Royces sold in California got worse gas mileage (10.4 miles per gallon) than did the ones sold in the rest of the country (11.6 miles per gallon). That was because the pollution control systems required by California ate up more gas. The gas mileage average could thus be raised if fewer cars were sold in California, but NHTSA found that "a significant percentage reduction in sales would have been necessary." In 1979, for example, 441 of some 1,205 Rolls-Royce models sold that year went to California buyers.

The final argument for giving Rolls-Royce the exemption it wanted came in the analysis of just how much extra U.S. demand for petroleum would develop from such an action. NHTSA estimated that "over the life" of the roughly 2,354 Rolls-Royce models sold in this country in 1979-80, the United States would be consuming an additional 60.9 barrels per day. "To give a perspective on these numbers," NHTSA said in its notice, "the fuel consumed by passenger automobiles in the U.S. is about 15 million barrels each day." Case dismissed, and we certainly expect the exemption to be granted.

Rolls-Royce was not so fortunate in its attempt to get a two-year waiver from U.S. air pollution standards for its 1981 and 1982 models. The Environmental Protection Agency, noting that Rolls-Royce met the standard with a test vehicle, turned thumbs down on the request.