The answer is a highly qualified “yes.” As in, yes, your older Peak 1 will burn unleaded gas. But not for long. Unless it’s specifically labeled “dual fuel” (and many later Peak 1s are), then the unleaded gas will fairly quickly clog up the generator. White gas, you see, is basically a highly refined version of auto gas. In particular, unleaded gasoline oxidizes more quickly than white gas, resulting in the formation of gums, varnishes, and other crud that can foul a spark plug or a stove.
Indeed it’s true that Coleman fuel (white gas) costs substantially more than unleaded fuel. That’s due in part to the more limited market for the stuff, but also to its higher degree of refinement. For the price of a new stove that would take unleaded fuel, you could run white gas through your older Peak 1 for a very long time and still come out ahead. Your break-even point probably is on the order of ten gallons of fuel or more.
Or, you could get a Coleman Feather 442 Dual Fuel stove. It’s a nice little single-burner stove with that tank-below-burner design that some campers like. Coleman is closing them out for $40聴a good price (www.coleman.com). So you could save dough on the stove, then let your inner cheapskate run wild with unleaded gasoline.