Update:

15 gallons gas
250 odometer miles
250 X 1.07 = 267 miles actual
267/ 15 = 18 mpg

This is the first time my mileage hit 18 mpg. Driving conditions were 25/75 city / highway. I should mention the city portion is under 45 mph with limited stops, mainly forest service roads. Fully loaded with camping gear, did manage to use a forest service truck scale, total weight with me in the truck was 2150 lbs.

Update: The scaling of my truck is now in question, the curb weight of my truck is advertised at 3776. So either the scale was malfunctioning or I didn't center on the scale. Reference: http://consumerguideauto.howstuffwor...0-blazer-6.htm

 

I managed to hit 19 mpg today!!! I installed one of them spacers last week under the throttle body and didnt think id actually gain anything. But i guess they do work fine for the tbi setups. The ones for the vortec engines are useless. So +1 mpg for spacer.

Not many people are posting in this thread,but ive been keeping a eye on it. keep us updated.

 

A thought I am having is the elevation of the roads in relation to fuel usage. I am wondering if the MAP sensor is seeing thinner air and adjusting the fuel ratio to a leaner mix? In the test I have done were my MPG was around 15 the elevation is below 1000 feet. The tests with 17+ MPG are in a region where the elevation is 3000 feet and above. I can data log the sensors now, so I'll make a comparison between low and high elevation next time I am up there again.

 

The ECU will adjust the AFR (air/fuel ratio) based primarily on the O2 sensor readings, but the MAP does also have a pretty big job in there. At higher elevations, engine power won't be as high even though the ECU adjusts for the elevation. I wouldn't think that elevation would help matters.

 

Update:

14 gallons gas
235 odometer miles
235 X 1.07 = 251 miles actual
251 / 14 = 18 mpg

Driving conditions this time were 25/75 city/highway. Only thing new is I placed the IAT sensor outside the cold air intake next to the plenum, while connected to the OBD1 port I can see the sensor is reporting approx. 105F.

 

Have you thought about switching over to full synthetics in the rear end and engine? Ive coming close to doing it myself.

 

well chris, the last time I switched to synthetic oil in a different car it ended up leaking out several seals. So I am a little cautious about switching, but I have already replaced engine, trans and rear diff with non-synthetic fluids. My next move is going to be spark plugs, I know this topic has been talked to death, right now there are ACdelco's in the engine, gap (50).

Did a check on the fuel pressure tonight and all is good, static pressure is holding @ 62+psi with key on. Leak down for 10 mins is less than 5 psi so that is all good. I am still looking at the running pressure being maybe a little low, at idle the pressure is 52 psi. What I have read says that spray pattern degrades rather quick with even a 2 psi drop in fuel pressure, 54 psi is about as low as you would want the psi. The regulator is non-adjustable so either my gauge is out of range or the regulator is set low.

Over at my data logging posting I am starting to learn about BLM and cells, there might come a day when I decide to do some brain surgery on the eprom. I think in the long run this might be the best way to improve MPG.

 

Update:

13 gallons gas
162 odometer miles
162 X 1.07 = 173 miles actual
173 / 13 = 13 mpg

Driving conditions this time were 75/25 city/highway. Did some trailer hauling this time, loaded with gravel and top soil. Even so, with the extra load I am baffled why I am only getting 13 mpg. If anyone has ideas why or what I can look at to improve my mileage please let me know~

 

ouch 13 mpg. I towed a 3000lb trailer for 2 days got 15.8 mpg on my 91 tbi 4.3. I may have already read it but i forgot,what gearing are you running?

 

Update: 4th July camping trip

First fill up

4.5 gallons gas
89 odometer miles
89 X 1.07 = 95 miles actual
95 / 4.5 = 21 mpg

Driving conditions for this leg to the camping spot were all highway at 55 mph. This is the first time I could test all highway mileage, I should add there was some drafting behind the big trucks on this leg.

Second fill up

13.5 gallons gas
232 odometer miles
232 X 1.07 = 248 miles actual
248 / 13 = 18 mpg

Driving conditions this time were back country roads, with some 55 mph driving. The bulk of the driving was 35 mph around my camping spot. I did manage to weigh the truck this time at the weigh station, 4600 lbs is what it came in at fully loaded. There are a couple of things that are different from my around city driving at 35 mph and the mountain driving at 35 mph. One is the stop and go, lights and such, the other is elevation. There is a big difference between on average 15 mpg in the city and 18 in the mountains. Part of it has to be the stop and go at the lights, I have been watching the BLM cells as they change and this must have something to do with gas mileage.

(trip gas mileage home still pending)

Chris, the gears are 3.42