x2 on staying away from Fram. Wix makes a solid filter. Amsoil has a new air filter that supposedly filters better and comes with a 100,000 mile warranty. I believe its a paper filter and just needs to be vacuumed off every 20k-25k miles.

My 2000 Blazer 4dr 2WD gets 21-23 mpgs, but thats because I drive like a grandpa and its got a 3.08 in it. It gets about 18 mpgs if I drive it like I stole it.

As an update, the change to K&N filter, oil/filter change, and new AC Delco platinum plugs has definitely helped. My truck was getting 13.49 mpg and now getting 18.05. I also found a report from the GM engineers that changing the gear ratio has almost no effect on gas mileage. Seems only towing rates change. The premises is that mileage is based at a 48 MPH average and anything higher only cuts into fuel economy by as much as 1.5 MPG per every 10 MPH over 48. Here is a link http://www.trucktestdigest.com/axle%20ratios.htm
I still want to play around with changing the fluids in the transfer case, tranny and differential and go to synthetics. Also thinking about changing the tires and tread pattern and using the higher pressures.
The way I see it, I have already paid for the cost of the parts in six weeks of average driving.

Easy upgrades
 

Ya, there are a couple things you should do. Replace the trans filter, fuel filter and air filter. Replaced all of them, and i'm gettin 20mpg hwy. Now the biggest thing would be a throttle body spacer, which from jegs.com was priced at $50. It gives 15% more torque, 10% more horsepower, and 8% more gas mileage. Now, I get roughly 24 hwy. Very cheap things that'll run you not even $100 and I get 10mpg more and much more power.

Throttle body spacer dose not help with the Vortec motors. I had one and it made my truck run slower and burnt more fuel. I took it off and i runs way better. Its a waste of money.

that's a crock of s**t! my '98 (that only had 158K/98 miles on it when i bough it last Christmas) gets 415 kilometers to a tank (that's 258 miles to 16 gal, or 60L), and it makes no difference how i drive it. i've driven on the highway, with the cruise set @ 115K (72MPH), and still only got 418 kilometers to 61.3L of fuel. driving combined city/highway (30%/70%, respectively) i only see a decrease of maybe 25 kilometers (15 miles).
the only way i get better fuel mileage is to stay off the highways, and only drive on country roads, where the speed limit is 80K (50MPH), and again, that only nets me an extra 50K (31 miles).:icon_shrug:
these 4.3 are just typical of (most) North Americain vehicles. don't get me wrong, i luv Detroit iron, but we all know these things are not bought for their fuel efficiency.:icon_razz:
we own them because they fit what we need, a truck we can do some work with, but aren't as big as my Burb, therefore, more convenient.:)