2000 blazer 4x4 ls v6

Why am i only getting twelve miles to the gallon? even highway driving is terrible on gas i just ordered new E3 plugs and wires and also a new muffler (thrush glasspack) the old muffler would rattle on the inside of it. and a new tailpipe so i could weld it on easily. but are there any known issues for mileage that bad and if so how can it be fixed i appreciate it!

and i ordered a new fuel filter as well

 

wow thats worse than what I get and I have 31's sounds like something in your fuel system is acting up

 

Put a good tuneup on it and make sure your tire pressures are up to snuff and the front end doesn't have worn parts/alignment issues. There are no miracle parts/repairs to improve mileage on these things. That said does the truck seem to run well in general? There are issues that can hurt the mileage like a bad fuel injection spider for example but you'll notice other issues like misfiring, gasoline smell. I lost 2mpg when they started adding ethanol to the gas years ago.

 

Sounds like a fuel system problem to me too... I would start by putting a fuel pressure gauge on it to see where the pressure is at.

 

If your getting that bad of gas mileage something is wrong.
Do you have any active codes?
do you do your routine maintenance like oil changes, air filters, checking tire pressure etc.

 

No never had a code pop up ever since i have owned this truck it seems to get terrible gas mileage it runs like a champ tho it just seems to suck down fuel no fuel smell or anything odd like that.

yes i do my own maintenace oil change every 5 to 3k miles and air filters every 10k or so