I read this thread a couple weeks ago but couldn't respond til now. I bought a 2010 Mazda 6i with the 2.5 and MT on the 5th of July. Love the car but noticed a grind occasionally when shifting 1-2 and the whole shift mechanism feels rather clunky. I own 5 Mazda 626s all with MT (2) 89s and (3) 91s, One of each year is on the road. The others are for back up and parts. Anyway they all use Dexron as a manual trans fluid. When did that idea change. I used slick 50 plus the Dexron when I worked on them at some point. I don't know if it would make a difference on the M6 since the Trans is a whole different mfg. Besides the shift problem I am getting a vibration between 1800 to 2100 RPM. Above and below it runs smooth. Since I bought the car from CarMax and its on the 30 day warranty, I took it back yesterday and they sent it to a Mazda Dealer in Richmond. The technician at CarMax agrees with me there is a problem and while I was there pulled up a page that included both M6s and Fusions. The grinding problem showed up and supposedly is linked to coasting. In order to increase gas economy, using the clutch or even shifting into neutral to save fuel causes a problem with the synchros. The other issue I have with this car in stock form is my 626 with the 2.2 and advertised 110 hp @ 4700/130 torque @3000 has more seat of the pants Zoom than this 170 hp @ 6000 rpm and 170 torque @ 4000 rpm. The power band is wrong and the close gear ratios are useless. Don't get me wrong, I do like the car but what was Mazda thinking in the design room. I rented a 2012 M6 with auto trans and @ 2000 rpm, I was doing 60 MPH. in this M6 w/ MT I got 45 MPH at 2000 rpm. Go figure. The problem with the AT is it downshifts too easy wasting gas.