Mobil Oil Co., under heavy jawboning pressure from the White House, agreed yesterday to forego $30 million in price increases it otherwise might make between now and the end of September.

President Carter had publicly excoriated the company for being out of compliance with the administration's voluntary price standards during the third quarter of 1979 to the tune of $45 million.

The tone of yesterday's statement by the White House was quite different. however. Mobil had "endeavored to interpret and apply the price standards in good faith . . . . honest differences of interpretation caused . . . . different conclusions," said the statement ready by Press Secretary Jody Powell.

Mobil had insisted on such language as part of any compromise settling the dispute, administration sources said.

The company had contended all along that part of the extra $45 million in revenues above what the standard allowed was due to usual spotmarket purchases of home heating oil in the second quarter of 1979 in response to administration pleas that the fuel be stockpiled for the coming winter. When the company started selling the fuel in the third quarter, it accounted for $15 million of the excess, Mobil said.

The administration's Council on Wage and Price Stability repeatedly had rejected Mobil's explanation on this point, but Powell said "we felt there was enough credibility to settle for the $30 million."

Whether the settlement actually will cost the company anything is not clear. In effect, Mobil will be permitted to earn $30 million less in the coming six months than it otherwise would be under the price standard. However, with the market for virtually all petroleum products softening, and with both refining and retailing margins begining to decline, market conditions could force Mobil that far below its allowed levels anyway, analysts said. The $30 million would be equal to less than one cent a gallon on Mobil products, according to one estimate.

Mobil was in compliance during the voluntary program's first full year, which ended with 1979's third quarter. But the COWPS maintained that its rules required compliance for refiners on a quarter-by-quarter basis

Separately, President Carter met with representatives of the nonferrous metals industry and praised them for their price restraint. "My request to you is to continue your request to you is to continue your responsible attitude," Carter declared.