Breaz

Hello all

I have a 2006 ext cab Silverado with 130k.
New tire at 35 psi, spark plugs, spark plug wires and K&N air filter.
Have had an alignment done .

My problem is this.

I used to get around 400 to 450 on a full tank mostly highway.

but slowly it has dropped down to 280 to 320.

No engine light, starts fine idles even better.

Running Castrol Edge ALL fluids changed (trany, diff all the rest)


i don't know what to do to get it back up even close to the roiginal mileage.Maybe injector cleaning? I'v tried almost everything else.

Any help appreciated.


Thanks in advance

zm1040

Did you get different treaded tires? Have you increased your average speed? Were you using cruise control before, but are not now?

AutomediaJoe

are you carrying around a bunch of extra gear in the back seats or storage areas? are you doing a lot more carpooling? weight can be a serious killer when it comes to gas mileage

Mille Racer 69

So can tire pressure.
Is your tire pressure lower now than it was with your last set?
Also as mentioned the tread pattern can make a big difference too.

Breaz

Thanks for the reply guys

I am using cruise control like i always have
the tire i put on are more aggressive then the originals
my load has gotten lighter i no longer carry all my tools around as i built a shed just for that reason (i am a carpenter)
My tires are Goodyear Wrangler Territory 265/70R17(i think) at the same or very close to the originals PSI
just checked they go up to 50 PSI shop put them at 35 should i run at 50? truck sticker says 35, 50 seems high

the mileage it seems has been decreasing very slowly


Thanks

Hunt4X4

where do you buy most of your gas? also check your fuel to air ratio. may need to check your gear ratio. make sure you have good timing with the spark plugs, if not fix this with a tune. Also take off you air intake, exposing the throttle, and flip it open to check how much engine grime there is.

Breaz

I buy my gas at Esso or Shell i don't have many tools as far has truck diagnosis what is the easiest way to check air/fuel ratio?
I thought the timing were all done by the computer and thet they were not adjustable.

I will check the manifold and see whats going on inside.

Thank you very much.

Hunt4X4

Shell is good, for the air to fuel ratio im pretty sure you can take it to have a dyno and figure out, not sure how to do it myself. And yes the timing is not going to be easy to change if you even can, i just know that if the computer isnt getting good readings from air intake and stuff like that it wont fire correctly. thats why if you unplug the wires to your air intake and you turn on the engine, it will knock real hard and wont sound normal at all.
my uncle also had a problem like yours and is replacing his injectors currently.

gas mileage is tricky

Breaz

ok i looked around in the throttle and took it off, there was a little bit of black oil? maybe sticky anyway cleaned it the best I could I think the next step is probably injector cleaning.


thank you for the replies I'll let you know of any changes

country_09

run some seafoam through it..what plugs did you use on it? and make sure all the plugs and wires and snug in there so all of them are firin like they're suppose to be. the tires will have an affect on the mileage but not near as bad as what you're seein.