THE NATIONAL TALENT for burning up oil is reaching new heights. The Federal Energy Administration, which tries to keep track of these things, says that in the month ending in mid-August, American oil consumption was up a resounding 8 per cent over the same time last year. Part of it, as you suspected, is the call of the open road and the effect of the vacation season on gasoline sales. But a greater part of it is the sharp increase in the use of heating oil.

Heating oil? In the middle of the hottest summer in years? Oddly enough, that's correct - and the explanation constitutes a warning. It appears that industries all over the country are getting ready for another shortage of natural gas, and they are moving to other fuels. The simplest alternative for most of them is heating oil. They all know that American production of natural gas has been slowly declining in recent years and that, if the weather gets cold, priority will once again be given to residential customers. The industrial consumers are learning not to rely on gas.

President Carter's energy plan takes it for granted that natural gas supplies will continue to decline over the next decade. To make up for it and provide for economic growth, the plan relies mainly on coal. But coal production is not expanding as the administration had expected. The epidemic of wildcat strikes continues in the Eastern coal fields, and the chaos within the United Mine Workers is far beyond any easy resolution. The probability of a nationwide coal strike in December seems to be very high. So far this year the mines have barely maintained last year's production level, let alone embarking on the accelerated expansion that the Carter plan requires.

Instead of coal, the American economy is shifting increasingly heavily to the one source of supply that is readily accessible - imported oil. From the customer's point of view, it has a lot of advantages. There are no labor troubles, no disruptive political quarrels over price controls, no unfamiliar technology to cope with, no intricate licensing procedures and relatively simple environmental constraints. It would be the perfect solution to the energy squeeze, but for two things: It's by far the most expensive of all sources of energy, and nobody knows whether or when some of the exporters may choose suddenly to turn off the supply for political reasons.Americans keep worrying about the cost and the insecurity of imported oil. But at the same them they keep using more of it.