What synthetic oil is best for this car?

Depends on if you are currently using synthetic. If you have never used synthetic oil and have over 100,000 miles (or the vehicle was not maintained well), then you could lose oil pressure if you start now. Better to use a synthetic blend. Amsoil is often condidered the best, but can be twice the price of others and difficult to get. Mobil One is extremely good (O.E. in Porsche and Mercedes) but not as easy to find if you have your oil changed at shop. Pennzoil is rated very close to Mobile One, is a bit less in cost and widely available. High rating, cost and availability has me using Pennzoil.

mobil 1 is all i use. will never use pennzoil due to multiple bad experiences from family members with it.

Pennzoil says their Ultra full-synthetic has the best sludge-fighting formula, and nobody is calling them a liar. I switched my Sienna from Castrol regular to Ultra at about 210K. Now at 236K and it uses less than a quart between changes (5-6K miles.) No sign of any oil pressure drop using same viscosity as before (5W-30).

Valvolines maxlife synthetic blend high milage oil is a really good choice as well. It also comes in a full synthetic option. Ive seen this oil prove to extend life on engines up to 300k and beyond.