i have a N55 MT coupe with every single add on possible. when you turn on the car regardless if its cold start or not, the RPM will be above 1k for sure. What happens is your radiator, and intercoolers shut down when the car is off so it needs to warm up when you turn the car on. and that takes about 15-25 seconds. I always listen to my cars engine because i already know by hear when its ready to leave the garage. you never want to take out a car right away when you turn it on. those rent cars you are talking about........people drive those like go cars. so did i to be honest i had a 335i sedan diesel as a loaner and i drove the **** out of it lol. So heres an example, if you open your eyes in the morning can you run the marathon? no. so when people turn on their cars, most dont wait for the RPM to rest before taking off. even if your leasing the car, it does not mean you need to **** it up because you might be able to purchase it for a great deal. the best car investment is financing a car that you have been the only owner and you know yourself that the car has got no problems. I have owned a BMW since 2001 a e46 330i, 330i zhp, m3, and currently a N55 335i MT.
As far as gasoline, i have put nothing but MOBIL 91 in all my cars since 01 except maybe once or twice chevron or shell. if you keep up with the stats MOBIL won the highest rating for gas recently. I never let the dealer change my oil i have done it myself.