After roaring higher for most of 2012, the national retail average for gasoline dropped steadily since peaking on April 6 at $3.94 per gallon, according to Wright Express (WEX). It starts in May at $3.81 per gallon — nearly 14 cents below where it started in May 2011, the April WEX report states.

Most experts predict that prices could get as low as $3.50 per gallon as it is typical for prices to fade by about 10% after the spring peak.

Meanwhile, diesel prices are already above the threshold averaging $4.10 per gallon. Analysts believe that diesel prices will likely soften near-term but think prices could spike in the second half of the year, thanks to strong global demand and low supplies in the U.S.

For last month's report, click here.