Okay I just calculated my gas mileage. I couldn't even get 200 miles before I had to fill up my tank which only took 12 gallons. I'm only getting 10 mpg which is terrible. I know these cars arnt great on gas but it can't be this bad. I replaced the throttle position switch, got the carb tuned, replaced the purge valve and O2 sensor as well. Did the distributor cap and rotor, oil change and need to do wires and spark plugs but still that shouldn't be the problem as to why my mpg is so low. I do have a code coming up only when I'm driving for a bit which is code 45 which says it's running lean still and I have no idea why or if this could be why it's terrible on gas. If someone has any idea as to why my gas is so low and what I could do to make it better let me know please! What are other people getting for mpg on there third gen v8 firebirds or camaros by the way. I'd love to know

 

Your being very vague and your math is not adding up.. Give us the true figured MPG

Common range is gonna be 14 to 18 mpg around town.

You said 12 gallons, not even 200 miles.. How many miles?
120 = 10 mpg
150 = 12.5 mpg
170 = 14.1 mpg
190 = 15.8 mpg

 

Does it have an overdrive trans? What rear gears? Does it run good?

 

I drove 123 miles before I had to fill up and 10.25 mpg is what I found out that I get.

 

Yes it has overdrive and it idles perfect and drives great

 

Where would that power valve be located exactly i duno if I have one and the spark plugs and wires arnt great I'm replacing them on Sunday

 

Power valve is in the carb.
Is it running cool? They run richer when cold.

 

Well I'll tell the mechanics to look at the power valve tomorrow morning. And I don't think it's running cool, it starts right up normally nothing out of the ordinary

 

These cars aren't inherently thirsty, even with a 350. MPG in the mid-20s is to be expected, and reaching 30 is possible, if that's what you want to build and drive for.

 

Then there's definitely something wrong with my car cause I'm not getting near that

 

Okay well I replaced my plugs and wires and honestly I've driven like 69 miles and I've lost like a quarter of a tank already and the code 45 is still coming on. If I can't fix this problem soon I'm gonna have to sell my car and I really don't want it to come to that so any suggestions on what I should get checked now would be greatly appreciated!!