Spec is 5w20. I have a stash of Mobil1 in both 5w20 and 0w20. It has a smart oil-life gauge that considers driving style and conditions. It's gone between 8 and 10,000 miles each time so far, now at 64k.
The car is smoother and quieter now with new tires. It was a squish-mobile at the spec 32 psi but stable and responsive at the sidewall max 51. Not as solid as before but that was like driving on shopping cart wheels, in a bad way. The rubber was hard and there was no tread left.
The light weight is noticeable on speed bumps and parking lot entrances and rough surfaces. The suspension responds faster and transmits less to the body. The extra bit of sidewall I think contributes to the shock absorption as well.
There is a bit more "tread squirm", as is expected. I was at the wear bars before, now I have an extra 1/4 inch of new (softer) rubber at the car-road interface. It's noisier on cornering. I haven't pushed the corners yet as I haven't learned their on-the-limit behavior safely yet. I will...
As expected from any old tires to new ones, braking is VASTLY improved.