ALEXANDRIA, VA --- Diesel volumes at truckstops continue this year to decline over 2007 volumes, according to a fuel survey conducted by NATSO, an association representing 1,100 truckstops and travel plazas.

The survey also revealed a huge shift in purchases from premium and mid-grade gasoline to regular gasoline. NATSO's survey showed that diesel sales at truckstops in June declined 5.2 percent compared with June of 2007. In July, diesel dropped 4.5 percent compared to the same period a year ago.

In the petroleum industry, volume declines of greater than 3 percent are considered significant. The average diesel volume for a single truckstop location was 906,700 gallons in June and 898,109 gallons in July, compared with last year's average volumes of 956,784 for June and 940,403 gallons in July.

During that same period, truckstop retailers continued to cope with higher wholesale prices for diesel fuel. According to data published by Oil Price Information Service (OPIS), in June, the average wholesale price was $1.74 more per gallon than in June of 2007. In July, wholesale prices averaged $1.76 more per gallon than the previous year.

While diesel volumes continue to drop, gasoline volumes at truckstops have increased slightly. NATSO members reported a 1.5 percent increase of gasoline volumes for June compared with June of 2007, and a 1.8 percent increase in July. There was a large shift from premium and mid-grade gasoline sales to sales of regular grade gasoline in both months.

In June, premium gasoline sales dropped 17 percent, with mid-grade declining by close to 13 percent, compared with the same month in 2007. July showed a 19-percent decline in premium sales and a 16-percent drop in mid-grade volumes.

Like diesel fuel, wholesale gasoline prices also showed huge increases year over year. In June, wholesale prices for gasoline increased an average of $1.03 per gallon, compared with June 2007. Wholesale gasoline prices increased by $1.09 in July over 2007.

The survey shows a gradual decline in diesel volumes after a strong start at the beginning of 2008. In January and February, truckstop diesel volumes increased at a rate of close to 6 percent year over year. However, as diesel prices rose, volumes began to decline, and by March sales had dropped by 2.5 percent over the previous year.

Diesel sales slightly recovered in April, increasing just over 2 percent, but then dropped sharply in May, falling 5.8 percent compared with May 2007. NATSO is the professional association of America's $42 billion travel plaza and truckstop industry.