Welcome to the forum and as a fellow 89 300SE owner you will get used to the RPM's. My 300SE has 155K on it so yours is just broken in! One thing that is nice about the higher RPM's is that the car will pull hills on the highway better. There will not be any of that shifting/gear hunting nonsense that I get on my other overdrive equipped cars. I will get 20+ MPG cruising at 60ish. Enjoy and I look forward to seeing your car! She has spent a lot of time just sitting.