Contact Chase Customer Service, they will have the answer. Generally, these purchases earn their bonus based on the code of the merchant selling them, and not the item. If the gas cards were sold by a gas station that is coded as such then it should appear that way for the program. or try the following:
My Chase goes5% gas in July this year. make a purchase of 1 card at a gas station with you card. Then wait several days, and check your purchase on-line. And see whether they counted it as a bonus or not. It will show online as bonus points in addition to your 1% points, you don't have to wait for your end-of-cycle statement. I have been able to confirm whether specialty food vendors a were counted as grocery stores or not this way.