The average price for diesel and gasoline in the U.S. continued climbing for the 10thstraight week, according to data tracked by the Energy Information Administration (EIA), though diesel prices increased at a far slower rate than that of gasoline.

The average pump price for diesel in the U.S. inched up 3/10ths of a penny to $4.135 per gallon this week, EIA noted, with the West Coast and California experiencing the only declines of 2.4 cents and 1.1 cent per gallon to $4.399 and $4.466 per gallon, respectively. Overall, the U.S. average price for diesel is now 30.2 cents higher per gallon compared to the same week in 2011, the EIA reported.

Diesel jumped the most in the Central Atlantic region, climbing 2.1 cents to reach $4.196 per gallon – a spike that pushed the average price of diesel on the East Coast up 1.2 cents to $4.125 per gallon. The Rocky Mountain region witnessed the next highest week-to-week jump in diesel, with prices climbing 1.4 cents to $4.256 per gallon, the agency noted.

Gasoline took a bigger week-over-week upward bounce, climbing 3.1 cents to a U.S. average of $3.878 per gallon, which is 27.7 cents higher per gallon compared to the same week in 2011. Prices only declined on the West Coast and by a mere 9/10ths of a penny to $4.074 per gallon, EIA said.

The Central Atlantic region witnessed the biggest spike in gasoline prices, increasing 9.3 cents to $3.953 per gallon, while the Rocky Mountain region endured a 7.4 cent jump to $3.772 per gallon. New England followed with a 6.7 cent increase to $3.989 per gallon. Together, the big Central Atlantic and New England price spikes drove gasoline prices 5.2 cents higher on the East Coast to $3.879 per gallon, according to EIA's numbers.

Despite the two and half month run-up in fuel prices, the EIA said it still expects a decline to begin soon – especially for gasoline, as the gasoline market transitions from summer-grade to winter-grade gasoline specifications.

Higher crude oil prices, refinery outages, a pipeline disruption, and concerns over Hurricane Isaac's impact on the Gulf Coast – the major refining region for the U.S. – all contributed to higher gasoline prices during August, the agency noted.

As a result of those factors, EIA increased its average regular-gasoline retail price forecast for the third quarter of 2012 to $3.66 per gallon from $3.49 per gallon. However, as the agency still expects declines to occur for gasoline shortly, its retail price forecast regular-grade gasoline still remains muted at an average $3.58 per gallon for the fourth quarter of 2012 and $3.43 per gallon in 2013.

Diesel prices, however, continue to concern analysts. Tom Kloza, a senior oil analyst for Oil Price Information Service (OPIS), noted in a Fleet Owner webinar late last month that diesel prices remain, in his words “ready to run.”

“We may be in for a short price break from about Labor Day to Columbus Day,” he added. “Then there is a real risk that the numbers will go much, much higher. [I am seeing] just about as compelling a case for a run-up in diesel prices as I have ever seen.”