Left on Thursday to see my parents, and filled up for $3.93, which we considered a good price. (Costco would've been cheaper, but it's a bit out of the way, and not quick.) Filled up in Henderson for $3.44 at that Costco yesterday morning (and added a bit more this afternoon before heading back).
Quite a difference, huh?
On a slightly related note, the Del Taco by the outlet malls in Barstow has no value menu. They had the basic taco, soft taco, and bean-and-cheese burritos for $1.39 and up, calling them stupid stuff like "Barstow soft taco." If I were the parent company, I'd drop the franchisee like a turd, prime location or not. Went across the street to McDonald's, and they were actually cheaper than most Inland Empire locations.