I have a 1995 Ford Taurus with the 3.0l V-6 Vulcan engine, and ~142K miles. I bought the car used with 17K miles off of a lease (so I assume it was broken in and serviced with conventional oil), but during my ownership, I've been using M1 5W30 (owners manual recommended viscosity), with an occasional switch to Amsoil, and one AutoRX treatment ~4K miles ago with Castrol GTX 5W30 (for 1K miles, and then straight back to M1 5W30)(*). Car is now due for it's regular 3K mile oil change, and I'm very tempted to go with Shell Rotella T 5W-40 Synthetic. Most of the posts on others with this engine (in Taurus and other Ford models) seem to have been recommending either staying with the 5W30 recommendation from Ford, or going to the 0W20 or 0W30 oils. Since I'm in NE Florida, we do see a few days of sub-freezing weather, but I don't think it's that big a deal. In 8 years of ownership, I haven't noticed any difficulty cranking during the cold weather with the 5W30 oil, so I'm sure the 5W40 Shell Synthetic will also do as well. Is the 40 weight "operating" viscosity too thick for this engine? The car has the crummy AXOD transmission that's been hard shifting for the last 50K miles. "Have you driven a Fraud lately?" Some piston valve in the tranny is corroded and sticking, although how an aluminum piston corrodes when surrounded by ATF is beyond me, and I've studied a lot about corrosion. Anyway, I know this motor is going to outlast the car, but I still am compelled to take good care of it. Cost to rebuild the tranny (required to replace the valve - Ford now makes it out of steel that doesn't corrode - talk about closing the barn door after the horse has left) is greater than the KBB wholesale value of the car, so it ain't gonna happen. Thanks, - Arved (*) Call me anal - I did one 1,000 mile A-RX flush with M1 oil. Then I reread the instructions here, and noticed that I was supposed to use a conventional oil. So this motor has had 2 A-RX flushes. At 3K miles since the A-RX flush with Castrol GTX, the M1 oil is still clear - I know, not a substitute for an oil exam, but there was noticable darkening in the previous 10 oil changes that hasn't happened yet on the A-RX'd engine.