The country’s naphthenic base oil producers supplied 10.3 million barrels, essentially matching their 2012 volume.

All told, the 2013 scorecard showed a gain of 2.3 million barrels over 2012’s tally of 57.5 million barrels. A large share of this year-on-year gain — 1.1 million barrels — can be attributed to one plant alone: Chevron’s API Group II base oil plant in Richmond, Calif.

Richmond can make 20,700 barrels a day of base oil — more than 11 percent of domestic paraffinic capacity — but the lube plant was forced to throttle back to less than half its normal operations when a fire crippled the mother refinery’s crude unit in August 2012.

The lube unit sustained a feeble pace for nine months, until resuming full output in May 2013. After that, it seemed determined to make up for lost time and barrels. Richmond’s base oil production in first-half 2013 was 1.8 million barrels, the EIA data shows; in the second half it nearly doubled that by streaming 3.5 million barrels.

Other paraffinic refiners quickened their stride as well in the second half of 2013. Of the total 49.5 million barrels of paraffinic base oil reported to the EIA, 22.8 million was manufactured in the first six months, while 26.7 million gushed in the year’s last six months.

The Energy Information Administration includes only virgin base oil in its refinery production data, so the numbers above do not include rerefined base oil output. Rerefining accounts now for 5 percent of U.S. nameplate capacity, according to Lubes’n’Grease magazine. Only a couple of rerefiners disclose their actual base oil output, but more than one boasted of running at near-capacity rates during 2013.

EIA also collects and publishes data on refinery output of wax, a byproduct of base oil manufacturing. For 2013, it pegged U.S. wax output at 3.0 million barrels, virtually unchanged since settling at that mark in 2010.