I discovered why some get better gas mileage...
 

Just wanted to point out an observation I made while driving home from work a little while ago. This only applies to Auto G's. I think I know why some get better gas mileage than others. While you are in manual mode on the tranny, it does not lock up the convertor - ever. You have to be in drive for the Torque convertor to lock, which lowers your RPM's. I was driving on the highway with the cruise on 69 MPH. I was in drive, and my RPM's were at about 2750. I switched to manual mode (of course it defalted to 4th gear), I selected 5th and left it there - all without touching the cruise control - so I was still going the same speed the whole time. My RPM's continued to stay at about 3000 while in manual mode in 5th gear - and the T.C. never locked. I suppose they do this because they assume while in manual mode you want the quicker response of the engine/trans when you hit the gas. I suppose that if you leave it like this over a long distance trip, if would cost you a couple MPG at least. Just thought I would share this with everyone. I have never seen it talked about or mentioned in my 5 months or so on the forum.

I am a brand new member/owner of a G35 and I was curious what kind of mileage most people are getting with the auto sedan?

The TC locks for me - 2003.5 - in MM mode. I notice it more now because of the exhaust (with the coupe mid-pipe) drones when the rpm's are lower and forced to stay lower than if the TC was not locked.

well, I have a 2005 G35X, so maybe they changed something since the 2003 model year.

In reply to the other question about gas mileage, my X gets 24.5-25 on an all-highway trip at 78 MPH cruise. With mostly city it gets around 19 MPG. Both of these calculations are from the NAV system.

They did change the manual mode in the sedans for model year 2004.5 and up. The manual mode in the sedans pre-04.5 was really a top gear selector and NOT a true manumatic. The newer sedans now have a true manumatic just like the coupe. That explains why some peoples sedan has tc lockup while the newer sedans do not.

wicked!

I've always wondered why the TC can't be locked at every opportunity in every gear?
That would improve efficiency wouldn't it?

I've tried using the Manual mode to save gas by shifting as early as I could. Turns out you can't upshift until you're above 2000rpm. With the delay, Manual mode is almost useless for this task.

I've tried using the Manual mode to save gas by shifting as early as I could. Turns out you can't upshift until you're above 2000rpm. With the delay, Manual mode is almost useless for this task.[/QUOTE]

You need to PM Gordgee and get his 10 wire grounding gear kit. Do a search. It's one of the best AT mods you can do.