2000 4.3l envoy

[2000 envoy]

hello everybody. just a few simple questions hopefully someone can answer. as everybody know 4.3 offers adequate hp but less than amazing mpg. is there any mods such as bolt-ons or tuners that you have tryed? if so what were they who made them and what were the results. looking for better mpg! any help would be much appreciated.

[junior3382]

Welcome, if you open up the air flow, it helps with these engines. Now until recently, I never had this issue myself. I have driven a 99 Silverado, 03 Astro and 01 s10 with this engine, and owned a 1995 s10 with the same 4.3l that all got better then 24mpg no problem. Now the 98 blazer I own sucks it down like a baby drinking milk! I am lucky to get 15mph, so I know how you feel. I am not sure if it was a design flaw in those SUV's from Chevy or a characteristic, but they are all the same. But like I was saying, open up the air flow, both in and out of the motor and you will see and increase... New air intake setup, new higher flow exhaust system and some like the throttlebody spacers. Now it can get expensive, but in the end it is less then trading it in for a new one, and not to mention it will sound and run better too. IMO. I wish there was an easy and cheap fix to this you could buy and install, but I have not found it yet. Keeping up on tuneups and oil changes will at least maintain what you have. hope this helps. Others on here might have other ideas, but these mods are what I have seen work the best.

[ukrkoz]

well, i have been researching improved mpg for yrs. here's simple facts i found so far:
1. this is how gasoline engine works: MORE OXYGEN-O2 SENSOR DETECTS THIS-ECM CORRECTS BY ADDING MORE GAS=MORE POWER. period. please, notice that sacramental MORE GAS.
2, from personal experience: adding cold air intake to my 2004 honda cr-v dropped mpg by solid 10% immediately.
3. i am not sure about making engine breath better by installing magnaflow or such. i think, the 1st point will kick in either way.
4. IF ENGINE IS RATED FOR 25MPG AND DOES 15, THERE'S SERIOUS PROBLEM WITH THAT ENGINE. something's not right, and badly. lost compression, clogged everything that can be clogged, bad spark, timing, you name it. it just does not happen without a reason.
5. from personal experience, what DOES improve mpg: humane driving style; switching to fully synthetic lubricants; switching to HALO plugs; installing high air flow filter (NOT COLD INTAKE); maintaining your tires pressure at border line highest pressure for comfortable level; switching to low rolling resistance tires($$). i fixed my cr-v's mpg by adding 3 oz of acetone per tankful. does not appear to make any difference on my silverado. but even just with above the mentioned "mods" i have best mpg for the truck - 17.5/22.

[junior3382]

I have had sucess with increase air flow. I put an exhaust and intake along with a chip for my ECU on my civic CRX and I saw the mpgs clime from 39mph to about 44, AND I got more power. I do agree with the driving style and synthetic lubricants. I use full synthetic oil for years and have seen improvements with engine noise and with longevity. But that is a post for a different thread. meanwhile, I can see your point about the O2 readjusting... biggest thing is keep your foot out of it. I have noticed that even though everyother 4.3 I have owned has gotten much better mileage, everyone who owns the GM SUV's with these motors sees this kind of mileage. I thought it was just me. But here is an odd tid bit.... My recent motor replacement was done with a 2003 GMC S15 Sanoma motor and my gas mileage went up by almost 6mpg! So perhaps there was just a design flaw for those series motors? who knows.

[87c10slammer]

mine came out of a 03 safari and i cant complain. i get around 21-22 mpg. and thats with the chrome rims and tiny rubbers.