every since I installed a 180 degree t-stat, i've been getting about 2-3 mpg less, before i was getting an average of 25-26 and now im getting around 22, its tis something to expect from the colder temperatures and slighty richer ratio, or does the computer need a while to adjust, i always fill up at the same pump at the same station, and do the same amount and type of driving every week, i drive 600 or more miles a week so gas milage is very importatnt to me

I think it'* safe to assume that over half the cars on this forum run 180'*. And most cars here in good tune achieve 29-32mpg on the highway.

I'd be looking at plugs, wires, coils, and a possible O2 depending on the age/brand.

all of those have been changed within 5000 miles, except coils, and all were delco parts, and the problem happenend after the first full tank after putting the t-stat in, and i've been through three tanks and keep getting 22 or 23 mpg

It is also possible, since technically our engines were designed to run at the slightly hotter temperatures that it is running "slightly" less efficiient. Although it has not been the experience here that mileage would drop off that noticably.

i guess ill drive it for 2 or 3 more tanks and see if it improves any, if it doesn't then i'll put the 195* back in and see what the milage does, i'll keep u updated

Putting the 195 back in you'll probably see the mileage come back up. Or it'* possible that with summer here you are seeing higher air temps and that is driving a lowered amount of timing/power and less mileage.