I recently purchased a 1994 SC400 with 91000 miles. I really enjoy this car and have a couple of questions for the board. First of all, at highway speed, say 75mph, I have noticed that the engine rpm is about 2750. On our Dodge Caravan with a 3.3 litre V6, the engine purrs along at 2250 rpm at 75 mph. Why would a V8 need a higher rpm at highway speed compared to a fairly peppy V6? Secondly, the car came with Bridgestone Potenza tires which seem kind of noisy at highway speed. Is this normal or should I invest in some new, quiet tires? Recommendations please.