Tech Question

Hubby-Eric and I are going on a road trip this summer. We're going to basically shoot down I-5 from Seattle to Monterey. We're hoping to gas up the car as cheaply as possible, so we're going to try to hit Costco along the way. Here's the technical part: does anyone know of a map that shows the Costco stores along the I-5 corridor that sell gas, and if not, does anyone know how I can map the stores in, say, Google maps? I have the addresses of every Costco store in all three states, but I don't know which ones are actually near to I-5 just from the addresses.

I wish we had a bio-fuel or hybrid car for this trip. Or just something that would save us some money on it. But even with the rising fuel prices, driving for the two of us is still cheaper than flying, and way less hassle and annoyance. I hated to fly before 2001, I haven't flown since. Not out of fear, but because I hate being crammed into a seat too small for legs, then have the idiot in front of me recline his seat into my face so I have no room (and no, reclining my own seat doesn't help, just makes me more airsick). If the seats in airplanes were made for real people and not some inhuman ideal of what a person ought to be like, I might actually enjoy being on a plane.

But I digress... does anyone know how I could map those Costco stores?