Gas in Estes Park is often 20-30¢ more per gallon than it is in larger towns in Colorado, and close to the most expensive in the US. YIKES!
If you can, fill up your tank before you get here... Lyons and Loveland are the last cheap places to buy gas. (f coming from the west, your best bet is probably somewhere along the Interstate. Gas is available in Grand Lake, but it ain't cheap there either.)
So, if you can avoid it, don't buy gas in Estes Park!
That said, however, you shouldn't leave Estes without a tank that's at least half full if you are planning on driving over Trail Ridge Road. The nearest gas via Trail Ridge Road is in Grand Lake, and that's two hours away with the potential for lots of stops and starts in between for scenic overlooks, critter watching, slow motor homes - you get the idea. There is no gas available inside Rocky Mountain National Park.
If you have to buy gas in Estes Park, there is rarely any difference in price between the six gas stations, with the exception of Murray and Sons, which tends to be cheaper:
Conoco-Phillips Schrader's Country Store 561 Big Thompson Ave, (970) 586-0235 Conveniently located downtown, below Safeway and across the street from the town Visitor Center. Your basic gas station. As of January 2008, they are closed for remodeling.
Conoco-Phillips B&B 531 S Saint Vrain Ave, (970) 586-2468 A little bit south of downtown Estes Park on Highway 7. There is a small deli inside and a terrific video rental store next door. This is also where the Rent a Car is located.
Shell 534 S Saint Vrain Ave, (970) 586-0193 Also a little bit south of downtown on Highway 7, this is the only gas station in town that has a car wash. Both self service and full service washes available, and there is a vacuum too.
Murray and Sons 531 S Saint Vrain Ave, (970) 586-0193 Also a little bit south of downtown Estes Park on Highway 7, this is an "off-brand" gas station that often has the cheapest price in town.
Shell Tiny Town One Stop 860 Moraine Ave, (970) 586-7867 Spitting distance from Rocky Mountain National Park and the Conoco station (below). Free air! Inside is a Blimpie restaurant (sub sandwiches) and an A&W (burgers, fries, and root beer), plus Piccadilly Circus Pizza. Next door is my favorite mini golf in Estes.
Conoco-Phillips National Park Village South 900 Moraine Avenue, (970) 586-2139 Last gas before entering Rocky Mountain National Park. Conveniently located in the same parking lot as the nearest grocery store to Rocky Mountain National Park. There are also a restaurant, giftshop, laundromat, and liquor store in this complex.