[Beav]

More than likely the gas had no effect on those codes, especially if it was a one time thing. One or more of the codes could be historical, as you anticipated. When a fault causes the MIL to illuminate and set a code it isn't the result of a one-time situation, the fault had to occur more than once (sometimes several times, depending on the particular fault.) Conversely, some faults will turn off the MIL if they don't recur in, say, fifty drive cycles (depends on OEM, programming, fault type, etc.) Some faults also only turn on the MIL for the moment, and not necessarily set a code. These type faults suck and can be elusive, usually the result of poor grounds or a failing ECM.

My advice would be to clear the codes and watch for any future MIL activity. Check the battery cables and make sure they are clean and tight - just because the car starts doesn't mean they have proper connections.