Diesel is completely different,..

 

I'm pretty sure the natural disasters which occurred in Japan the past few years put some restraint on the OEMs to develop new engines. Just look at both the Q50 and the IS, neither bought new powertrains to the table when a new model debuted. Agreed the Q50 has the hybrid, but it's basically carry over from the M35 hybrid.

The Q50 is going to get a turbo-4 in 1-2 years, and I strongly believe that the IS will follow suit. Everyone playing in this sandbox has to keep up with the Joneses (mostly BMW, but Audi and Benz have the 4cyl models too).

For me, the refinement of the overall vehicle is what stood out when comparing my current G37 to the IS250 I drove, and also the Q50. I'm not in dire need of the extra power from the IS350, but I would like a nice compromise.

 

My other car is in the body shop (not my fault at least) and I have had a '13 Mercedes C250 (4 cylinder, 7 speed auto) for a week so far. While I don't love the Mercedes enough to consider buying one it definitely handles better than my 2G IS 250 and is faster and am getting about 2 MPG better while driving more aggressively (it is a rental afterall!). Definitely will consider the merits of a turbo 4 in the next car purchase as was already open to it after using a family member's 2.0 Audi. Why not if can get a faster car with better MPG? BTW, it the motor sounds just fine and is very smooth even though I always say I like the sound of a 6 better. Lexus needs to step up the powertrain in the 250 to stay competitive.