Economist Peter Dawson did not fill up his car's gas tank with gas Saturday, and for a good reason.

"The price of gasoline is trending lower, so the longer you wait the less you'll pay," Dawson said.

In fact, in addition to cutting back his driving, Dawson is performing another modest act of conservation, which, if applied across the states, should help lower prices even more over time: he's not filling up his tank. If he uses 10 gallons in a week, he's replacing the 10, not filling the tank completely.

The above will help cancel-out the effect of a practice that's all-to-familiar to drivers: as soon as oil prices rise, gasoline stations immediately increase their prices. During the current oil shock, gas stations would some times raise prices 20 or 30 cents overnight, occasionally, more, he said.

The above practice is justified from a cash-flow standpoint, Dawson said, because gas stations are trying to prepare for the higher cost of the next gasoline delivery from gasoline wholesalers: a rise in oil prices means their next delivery is going to cost more, and to pay for it, gas stations "immediately raise their prices, so their cash flow isn't hurt."