Traveler6

You should use the lowest rated gas that gives you good performance. Try a tank or two of regular and keep track of mpg, performance, and any 'pinging' noise. Then try a couple of tanks of the next higher rated gas. And on to the premium. You will probably get a minimal better gas mileage from thge premium but you need to weigh that with the cost difference. Maybe you could use a mud-grade and have the best of both worlds. The onboard computer will override and compensate for any problems that you may have with the lower grade gas. Use the one that runs the best. I have several cars that are supposed to use premium and I have used regular in them all consistently. One has a few miles short of 100,000 miles on it and runs great. It also gets great mpg.

I spent a bunch of time looking around and talked with a few people. I ended up getting Michilin Latitude Touring tires for my RX. They seem pretty quiet and smooth. Much better than the Michilin Energy that came stock.