Join Date: Jun 2001
Location: San Diego Area
Programs: UA Gold MM, AA Gold MM, FB Gold, Marriott Plat LT, HH Gold, IHG Plat, WoH Discvst, Hertz PC
Posts: 1,871
From the T&Cs of the Hilton HHonors® Platinum Credit Card from American Express:
1. You will receive five HHonors bonus points per eligible dollar at qualifying U.S. supermarkets, drugstores, and gas stations that are not departments of superstores or warehouse clubs, and at restaurants, the U.S. Postal Service, and for wireless phone bill payments.
So pretty clearly the answer is NO. I did charge some Costco gas to my card in December, but never ran the calculations to determine whether I go 3 or 5 points. (I was only expecting 3.)