Hi, im new to the forum and blazers, i just recently bought a 2000 blazer its the "trailblazer" edition, it has 105,000. Before i bought it the owner had done a full tune up on it ( cap, rotor, plugs wires, etc.) when i first got it it was getting 19.5 - 21 MPG on the overhead gauge. But here lately it has been slowly loosing MPG, its down to 13-14 now. I have gone over everything, and i have replaced the fuel filter, and 02 sensors, but still nothing. So any ideas would be great.

 

check your tire pressure
ive heard that can affect mileage

 

Poor fuel quality? Winter mix fuel? Tire pressure? Clogged air or fuel filters? Leaking injectors? Poor quality O2 sensors? Improper plug selection?

 

Also have your driving habbits or locations changed. Like were you taking the highway to work before and now you arent. Or were you the only one in your truck before where now it full anything like that. Like I get right around 20 on the highway but if I get stuck in city traffic it can be way down to like 13MPG. Also when you did the tuneup what brand were the parts.

 

well it could be the winter mix fuel, but the tire pressure is good, ive changed the fuel filter, and the air cleaner is new, Whats the life on injectors? it has 105,000 on it, and the people i bought it from did the tune up, they used all ac delco parts but the plugs are those E3 diamond fire plugs, ive never used these before but ive heard there suppose to be good. and my driving conditions havent changed at all

 

There is no independent proof that shows that the E3 plugs do anything special. They will not last like a double platinum plug which your truck was originally equiped with. I am not saying that the plugs are your problem, especially if they are new.

You can try some fuel injector cleaner. Chevron Techron Fuel System Treatment Plus is what I use and have had great success with using in a preventative maintenance role.

Injectors themselves should last the life of the vehicle. It is varnish buildup that can cause them to leak. The injection setup on your truck stock has an electronic injector for each cylinder that feeds fuel through nylon hoses down to pressure actuated poppet nozzles at the intake port. These poppet nozzles can be problematic at times.

 

Never used them, but I see articles and posts on the 'net that say 'meh'. Best to stick with the AC/Delco Double Platinums. You'll probably find that the avg mpg on the overhead display won't match up with figuring the mpg manually.

 

Other areas to check arebrake calipers, wheel bearings, or a bad wheel alignment. Brake calipers can go bad and stick, and a wheel bearing going bad can drag as well. Those would be easy to check by jacking up the front end and spinning the wheels by hand. Compare drivers side to passenger side and if one is harder to spin, you have a good place to start looking for the problem. A bad alignment will usually show upas abad wear patternon your tires. Also might want to check for worn outsteering components and bushings.

 

clogged cat? Have you noticed a power lost?

 

It actually looks like it has a new cat on it, cause they have some horrible welds on it that have a couple leaks. I tryed to remove it but the bolts that connect it to the muffler striped off so i am waiting to do a full exhaust to fix this. But i havent noticed a loss in power just the gradual loss in MPG. It seems steady now at 13 MPG it hasnt moved.