Why does my gas mileage consistently suck? I get like 12-13mpg all city driving. I get around 16mpg highway. My car despite haveing new opti/plugs/wires/coolant flush/fuel pump/fuel filter/ filter cleaning/injector cleaning still eats gas like crazy. I use premium as well. The only other thing I can think of is 02's? Anybody else have any explanations.

Mods: 3.73's (yes i know these bring down mpg but not that much), bbk shorties, bb catback, ram air, shift kit. Thats about all the performance stuff.

I cant figure out why my mileage is so sucky, cuz i dont get on it all the time. Maybe a couple times a tank to like 60 or so.

-Michael

 

o2 can make gas mileage go down.

is ses light on?
has there been any tuneing done, something could be messed up.


if you have an exhoust leak it could couse the o2 sensors to give false lean readings. check for leaks

a leak may not turn on the ses light

 

Lay off the pedal man.



Yeah i would get car scanned. See what reading your o2's are putting out. If one is bad it will make you run really rich.

 

02's would cause a service engine soon light correct? I dont have a service engine soon light on right now. So, as far as i know that isnt it, but i was gonna replace them anyway. i do have a header leak, but that made the gas mileage even lower than that. I am gonna fix it on thursday though. But, it still suxs beside that.

 

Well i think if the o2 sensor is dead it will give you an ses light, but if its reading wrong it wont, but will still kill gas mileage.

Are you saying that 12-13mpg was without the header leak? What is it at with the leak?

 

I think its about 11mpg with the leak. I am gonna fix the leak on thursday and order some arp bolts. It wont raise it that much though. So, i am guessing i should try new 02's and see where that gets me.

 

Check your rubber inlet to the Throtle Body. That could be a source of air inlet, ask me hjow I know, lol,, and it looked like it was on properly from the top, but ripped underneath.

 

I have 2 severe header leaks (broken bolts , goes in on the 17th for repair , wish me luck !!!) and my car gets really ratty mileage , altho I have the lt4 hotcam kit so that might have something to do with it . I think I get around 12 mpg. My light is on tho , get front drivers o2 sensor every now and then and a 403 or whatever the passenger cat system ineffeciency light. Im hoping the latter is just cold air getting in there and throwing off the reading and not like a clogged cat or something. After I get the leaks fixed if I still get codes Im gonna put on some new o2's cuz I think its due anyways. Any guys here with lt4 kits ? what kinda mileage you getting ?