The average U.S. cost of diesel has increased for the fifth straight week and is at its highest level since mid-August of 2008.

The new U.S. Energy Department report released Tuesday shows the average U.S. price rose 5.3 cents in the past week to $4.157 per gallon. The hike also put diesel nearly 20 cents higher than the same time a year ago and is a pickup of just over 26 cents since the last weekly decline.

Prices increased in all regions of the country over the past week, with averages ranging from $4.032 in the Rockies to $4.334 in New England.

The biggest increase was in the Gulf Coast region, where diesel prices were 7.1 cents higher than the week before for an average of $4.068 per gallon. Average prices in other regions are:

• East Coast, $4.199

• Central Atlantic, $4.254

• Lower Atlantic, $4.133

• Midwest, $4.132

• West Coast, $4.303

California’s average cost came in at $4.361 per gallon.

Gasoline prices are rising much faster the diesel, increasing 13.6 cents over the past week to $3.747 per gallon, its highest price since last October. It has moved higher for seven straight weeks, after hitting $3.233 in early January

This came as oil in New York trading on Tuesday gained 80 cents closing at $96.66 per barrel, which is down a few cents from the same time a week ago.

Some analysts note the recent run-up in both diesel and gasoline prices this time of the year is unusual, considering the winter has not been especially colder than normal in many parts of the country. Some are blaming speculators for the hike, along with increasing exports of fuel. They caution that the increase in fuel prices could be the start of a longer series of higher prices that usually don’t happen until later in the year.