April RBOB prices slipped to a new four-day low this morning, pressured by outside market weakness, gains in the US dollar and sell-off in crude oil. While gasoline futures have pulled back as much is $0.13 from last week's high, US lawmakers have pressured the CFTC to investigate speculation in the energy markets. Some traders indicated the possibility of US gasoline demand coming under added pressure from rising fuel costs. The latest data from the EIA pegged average gasoline prices at $3.79, up nearly 8.0% from year ago levels.