On-highway diesel prices continued falling last week, although not quite as steeply as the week before.

According to the Energy Information Administration, the national average price fell another 4.9 cents to $3.948. A week earlier prices dropped 6.4 cents nationally. Diesel fuel is still nearly a dollar more expensive than this time last year.

Moreover, prices dropped in every region of the United States, with the Rocky Mountains taking the biggest cut at 8.1 cents. The Gulf Coast is still cheapest at $3.884, California the most expensive at $4.227.

The dollar once again weakened vis-à-vis the Euro as Germany considered dropping its push for an early rescheduling of Greek bonds in order to facilitate a new package of aid loans for the debt-laden country. This three-week high against the dollar pushed oil prices back up: Light, sweet crude for July closed at $102.70 on Tuesday, gaining 2.1 percent.

Additionally, crude oil prices were also pushed upward by a major pipeline shutdown in the U.S. A modest 40-barrel spill at a Kansas pump station along TransCanada's Keystone network led the operator to shut down the entire pipeline system, which connects heavy-oil fields in Alberta with the oil hub of Cushing, Okla., which is the delivery point for the Nymex light, sweet oil contract. Record oil levels at Cushing have depressed the front-month Nymex contract versus other contracts in recent months, and the outage on the network, which can deliver up to 591,000 barrels a day to Cushing, is causing the Nymex contract to regain territory.