I am looking at ways of increasing my fuel mileage on my 99 blazer 4x4 4dr. I have been doing a lot of work to my old blazer that last couple of weeks. fuel gauge issues, hunting down all the rattle and squeaks, (lower ball joint one upper ball joint, shocks, wheel bearing, getting all the lights working and etc.
so during all this I checked the mileage 90% was all in town driving and the old beast average 13.7 mpg, previously about 3 or 4 months ago with it was getting about 75% city driving it was getting about 16 mpg. But the last tank full of gas I was running some fuel additives to try and clean the injectors. I have been reading on some of the other threads the having your PCM tuned. The old truck got 132,000 miles on and I plan on driving it another 3 years possibly 4 years. Will getting the PCM tuned help my MPG in the next 3 to 4 year to make it worth having done?

 

First I would start by doing a full tune up. Change your plugs,wires,air filter, cap and rotor. Then I would clean the maf with maf sensor spray.
What size tires do you have on it? Always keep them properly inflated and lay off the gas pedal as much as possible lol. You may also want to check your upstream o2 sensors to make sure there not getting lazy.
Having said that, my 99 was getting an average of 16mpg mostly highway, after the tune up I'm now getting 19. I am having blackbear performance tune my pcm. The average increase in mpg is between 2 to 4 mpg. But the main reason I had mine tuned is driveability. Firmer shifts, increased power, torque management removed,etc. I will be doing a review after I have had enough time to give it an honest review.
Also, don't run ethanol gas! Its been proven you will see a 10% drop in fuel economy.

 

LOL... It's true from what I've seen that ALL the ethanol in 90/10 is wasted .. EPA doesnt care!

But where exactly would you suggest we buy this non-ethanol?

 

I have already cleaned the MAF I started there first, as for tires they are passenger 235/70 R 15's, and air pressure is to manufactures spec's, I have also keep the rev's below 2000 rpm's.
I have not checked the O2 sensors yet, I totally avoid any fuel with ethanol in it. I would rather pay more for the gas than replace fuel pumps every month. the tranny is a re manufactured one with a mild shift kit, if your foot is heavy the first to second will bounce your head off the headrest, so I am light on the pedal. the shift was pretty heavy when first installed it and I took it to the GM dealership and it adjusted to factory spec's (according to them)

I think I seen a thread had a DIY test for O2 sensors, I got to see if I can find it again.

I also only use 88 or 89 octane fuel in it. been down that road before.

 

I am lucky to have several stations close that don't sell that ethanol crap can you believe they are talking about adding more ethanol!
It sounds like you're on the right track, I would definetly recommend a pcm tune. All the full size gm guys swear by blackbear, so that's who I went with. But before I ordered it I made sure all my maintenace was up to date as far as plugs,etc. Most people will agree a tune is the single best bang for your buck mod. There are other places to get a tune, pcmforless,wait4me,wheatley,nelson. After spending hours reading reviews I went with blackbear. I also have a 2.5 inch flowmaster supper 44, high flow cat and just got my aem bruteforce cai!

 

What road is this? I just got a blazer and have rebuilt spider, done full tune up and then some, and it is still spittin out black smoke and idling like ****. Only codes are the o2 codes. I did question the level of gas I am using in the thing. Will that cause a check engine code on these things?

 

normally ethanol fuel is only 86 octane

 

I'm in Utah and have been filling it up with 85. Thought about bumping it up to 87, but after comment above I got scared.

 

ok another question looking at tune-up parts

AC Delco cap and rotor (no problem)
AC Delco wires ???? (do they need to be AC Delco???? or will other ones work and if so which ones)
AC Delco spark plugs (rapid fire? platinum ???)

I have head bad things about platinum plugs.
Why don't they list a normal plain ac plug for the 4.3 v6???

 

I just put the rapid fires in mine with cheapie wires cap and rotor. that doesn't seem to be my problem, and it does run a lot better than the autolite p.o.s.s that were in it when I got it.