I have a 99 blazer 4.3 with cold air intake, exhaust, and high flow cat.. I replaced my o2 sensors not to long ago and put new plugs in last winter... it seems that my fuel millage has droped ALOT, it had a 1/2 tank and then after work i went out side and started driving home and the next thing i know its barley above E., kinda flustered!!! when i replaced my plugs it looked like it had fairly new wires on it, none of them where in the connectors.. i have like 120,000 miles on'er. Any suggestions? thanks

 

That's not really anything to gauge gas mileage by. That could mean anything from a bad fuel gauge to a major fuel leak to a bad sending unit, etc. The only way to be sure of your mileage is to fill up, see how many miles until you fill up again, and divide the miles by the number of gallons to do the second fill-up.

 

Think of this...

You put a intake in, it breathes better, correct? yes
you put an exhaust on it lets air out better, correct? yes

Now since your breathing better and letting air out better wouldnt you need more fuel?

Think of it as if you breathe normally, then breathe fast and really deep breathes...your going to need more food(energy/fuel) to keep at this rate.

 

breathing fast is what takes more energy. i doesnt take a lot to breathe deep. driving fast is gonna require more fuel but driving normally, it shouldnt need more fuel b/c of an intake. the intake is mainly to draw colder air which mixes betterand more efficiently...

enough of the metaphors though, an intake and exhaust shouldnt cause you to get lower gas mileage. if it did, there wouldnt be so many people putting on aftermarket mufflers and intakes. and like Richard said, the gas gauge is very sketchy, if you park facing uphill vs facing downhill, the gauge will show very different readings.

 

i may have to check to see if their is a leak or sumthing. ive had the exhaust and intake for a year so i dont know why it would be crap a year later........it used to do what a blazer does on consumption of fuel ( haha ) and now its worse

 

Something Ive noticed with my blazer and my olds, that the gas gauge needle takes forever to move from full to 1/2 tank. But after 1/2 drops like a rock.

But have you actually figured out the gas mileage to see what you were getting as opposed to now?

--Jay

 

I usualy get around 50 miles per 1/4 of tank. usualy is right on.....