Hi, I'm Cy Chowattukunnel (in old country language, my last name means he who knows all about tires). I'm entering my 10th year at the Tire Rack. So far it's been a great ride. I've enjoyed working with drivers across the country and around the world.

Thank you.
Cy
We do not plan to do any track days or wild cornering with the R. It gets about 25 MPG short shifting much of the time 2,4,6. It seems geared low to me. I wonder about a lot of possibilities. If the Yoko Green tire made of oranges could really save me some fuel mileage and if they had some grip, maybe that would be a good idea for fast cruising, or is this thinking bogus. I do not think we want a dedicated summer tire. Could get the Pilot Sport AS, or save money and get the Conti AS, do not like Conti, but you guys say they are very good. What about trying to go to a taller tire, like a 45 section (or, to explore fuel mileage, how tall could you go, and then there is all that weight like a big fywheel). Perhaps a 235/40-18 Pilot Sport A/S. I believe it weighs the same as the 225 and is taller, and may even last longer because it is more tire. I do believe that wider tires have poorer Aero Cd, and can be heavier, and can have more rolling resistance, and can affeat steering and ride feeling every imperfection on the road. We can stay with stock size, or try to get better fuel economy and even ride. We will let the next owner be the one to take it to the track, I have an old Lotus 7 for the track.
Thanks Cy.
For your emphasis on efficiency and for a tire doesn't overly compromise steering response and overall handling I would look at a lightweight 225/40-18 tire like the Pirelli Pzero Nero AS see:
http://www.tirerack.com/tires/tires.jsp?tireMake=Pirelli&tireModel=P+Zero+Nero+All+Season&partnum=24HR80NASXL&vehicleSearch=false&fromCompare1=yes&wtpackage=true&affiliate=HK8
Taller sizes will hurt efficiency because of poorer aerodynamics. Taller sizes will also raise the center of gravity slightly negatively effecting how sporty the car feels.
The 225/40-18 Pirelli Pzero Nero A/S linked above weighs about 2 lbs less then 225/40-18 Michelin Pilot Sport A/S so that couple with experimenting with air pressures 3-5 lbs above the 38 front&back factory pressure should help with efficiency.
Cy
. The tries have been balanced twice/w a hunter roadforce balancer /w a litte improvement. Chevy customer service says the car was designed this way??? My question does tire rack sell a good allseason tire that doesn't vibrate at high speed without needing to be roadforce balanced?