[YukonCornelius]

I wanted to post this up since it's not the norm here. I have a 05 CTS-V that has a the Z06 LS6 and 6 speed. I have a larger than stock cam in it .580/.580 220/226 117lsa, full length headers, no cats, f.a.s.t intake manifold, ported 90mm tb ect ect.

Now onto what you guys care about. My current best full tank to date is 27.4 MPG. No engine off coasting or pulsing, not even much drafting trucks (rock chips). The car was loaded with stuff and a passenger doing a highway trip to New York (187 miles) a week of short trips where I was, the whole drive back and then some more driving around. I had all the tires around 50psi. My car has a setting for a live MPG display and from the testing I've done the thing is just about dead on. This isn't my daily so most of my usual driving is short distance and hard on throttle so I haven't made a effort to beat my full tank MPG record.

However, I have made two major ecomodder mods. First, Cadillac didn't use DFCO on this cars tune because a Cadillac is supposed to roll when you let off the throttle. So I have it set that DFCO will now engage in all gears except first at any speed and at any RPM and it doesn't feed fuel again until 1100 RPMs. This was about as low I could go and not have to worry about a possible stall. Next, and this is major, I found a way trick my PCM to accept the lean cruise that GM uses on some Australian cars. Going off my live MPG reader my car seemed to like a 16.3 AFR at cruise. And it gained 2-3 MPG from this when shutting it on and off while driving. I have the settings cranked up though, engaging lean cruise low at 40mph in any gear, and it will hold until I get about 1/3 down on the throttle. In good air by myself and on a flat highway I can cruise getting 41 MPG.

The one fault of this car is the stock gears are 3.73's. Oddly enough with my custom grind cam my car seems to get more efficient with higher RPMS when cruising. Doing 50-55 mph I have trouble getting my live mpg reading to stay at 30. If I bring it up to 72-75 I'm well into the 30's or even low 40's and can feel I'm using much less pedal. I'm going to make at road trip to Cape Cod next month and I'm looking forward getting a new best. I'm confident that I will break 30, 34 would make me really happy. I'm so tempted to block off my whole lower grill and brake vent ducts in the front but I'm a little self conscious about it on this particular car. I'd like to do a couple extra things before I leave though.