U.S. CAPACITY USE RATE 79.8 PCT IN FEBRUARY U.S. factories, mines and utilities operated at 79.8 pct of capacity in February, compared with a revised 79.6 pct in January and December, the Federal reserve Board said. The Fed previously said the rate was 79.7 pct in January and 79.5 pct in December. A surge in automobile assemblies in February and a gain in primary metals production helped raise manufacturing to 80.1 pct capacity from 79.9 pct in January. Durables manufacturing increased to 76.8 pct last month from 76.3 pct in January, the Fed said. Nondurable manufacturing eased to 85.2 pct of capacity use from 85.4 pct in January. Last month's rate was down from 80.2 pct in February, 1986. Fabricated metals increased to 81.4 pct in February from 81.2 pct in January, while motor vehicles and parts jumped to 83.6 pct from 80.0 in January. Primary metals rose to 67.7 pct from 66.7 pct in January. Petroleum products fell to 92.5 pct in February from 94.5 pct in January. Capacity utilization for mining rose to 75.3 pct in February from 75.1 pct in January, but was below the February 1986 rate of 79.4 pct, the Fed said. The use rate for utilities was up to 80.8 pct last month from 80.4 pct in January. Producers of industrial materials operated at 78.9 pct of capacity, the same as in January and December, but down from the February 1986 rate of 79.6 pct. The Fed said the decline in energy materials use and durables goods materials were the reason for the decline over the past year for producers of industrial materials.