I'm getting 20 to 23 on highway, and 16 and below (depending on how happy my right foot gets) in town. Thats with heads/cc305 cam/3:73's/2800 stall (it grabs good around 3000 and flashes to 3200). I HAD 3:23's in it, and thought the new gears would kill my highway mileage, but to be honset, it ended up being about the same. Now in town is a "whole nother story"!

Dave C.

 

How do you guys do it? Will tuning this pig with Edit help out any in the gas mileage area? I drive 90 % highway to and from work and I see at best 18/19 MPG? I have 273s and get 18/19 MPG so I have been so afraid to get 373s like I have wanted for so long. I have done all the usual stuff....fuel filter, pcv, plugs, wires, 02s and probably more that I cant think of. Please tell me your secrets

Rich

 

I drive from KC to Chicago all the time and its 480 miles. I leave with a full tank and fill up once. Then I am damn near on E right when I get home. So two tanks of gas equals 240 miles on one tank of gas. That blows! Whats wrong with our cars? What happened to the 26-27 MPH on the highway.....I damn sure aint seeing it.

 

superkia8 - Man, if your as stock as your sig indicates, and you're only seeing 18 MPG on the highway, then you need to start checking some things.. Basics first like air filter, fuel filter, etc.. If that checks out (which I suspect it will) then I would start looking for a bad (or semi bad) O2 in there. Aside from that, your trans could be slipping or you might have a converter going bad. I can tell you that the stall speed should have no impact on your HIGHWAY mileage if it's locking up properly. It should lock HARD in fourth, with a definate drop in RPM when it does so. If it's not locking hard, or feels "sloppy" then your bleeding off mileage in the trans (and generating a buttload more heat in the trans as a byproduct which kills the trans sooner).

I would have expected worse mileage from mine if I had gone with a bigger cam (IE less low end torque), but it's about where I expected with the cc305. I lock up at about 40 MPH (I lowered it in the trans tables), and I pretty much chug the car up to 60/65. I do notice a marked difference when I don't do that though...

Hope this helps you out..

Dave C.

 

Hey Dave, I have the stock convertor in it still and yeah the car is pretty much stock? I replaced the fuel filter also just forgot to mention it. I do know that my transmission makes a rattling or knocking noise sometimes when it is in drive with my foot on the break? I took it to a chevy dealership and they said it wasnt anything under my warranty, it was the trans mount. I replaced that about a year ago but I guess it could have broken again. But then when I climbed under there the trans mount was nice and snug. I just cleaned the K&N filter the other day so I will see if maybe that helps a little?

Well thanks for your help, I will post again if it gets better from the air cleaner.

Rich T