I had read an article a couple of years ago in Panorama which was a reprint from the late 1970s that was about a man who bought a used Porsche 911 and the previous owner told him "whatever you do, keep her above 4000".
Before this, when I purchased my 928 it was making all of this clacking noise that was driving me nuts. I posted it on the 928 forums and one reply was "take her down the highway, warm her up and run the piss out of her, then keep her above 4000 when driving". He further explained that carbon builds and clogs things up if you drive it like other cars. Once that happens, you have to run it really hard to clean it out. Keeping her above 4000rpm while driving around town keeps the carbon from building up and helps the engine run better.
After several people agreed with his comments, I made this a habit and the only time that noise comes back is when the wife drives her (keeps it in the 2-3Krpm range) or when it's about 500 miles to the next oil change.
The reason I wanted to bring this up is there's a lot of scepticism out there about what some say is "running the engine so hard". I've had some say "I could never do that to my baby" and similar comments. Others are concerned with lower mileage. Well, I finally got confirmation from the Porsche factory folks on my last mountain run so I thought I would share.
We have mountain runs occasionally with Porsches, Ferraris, BMWs & even a guy in a Pantera that are a blast. Last time there was a guy in a Cayman S who is a Porsche engineer. He had the car from the factory to drive it in every day situations to see how it performs (quite nicely I might add). As the day went on, we stopped several times and would just chat for a few minutes to break the stress of driving so hard through the mountains. At one of the stops I had the pleasure of talking to him and asked what he does for Porsche. As it turned out, he is an engineer who helps to figure out the causes of problems in engines. He tears them down after a failure or if there is a persistent problem and examines everything about it.
After learning about what he does for Porsche, I asked what the most common problem is. His answer was "I go to court for Porsche all the time when people sue us because the engine is running poorly, making lots of noise, sputtering, etc. We take the engine apart and there is carbon built up all over the place causing all of the trouble." I asked him what causes the build up and he said "Most of the buyers are older since a Porsche is an expensive car. The problem is they bought a race car and drive it like they would a Jaguar or Cadillac. They don't drive the car hard enough to burn off the carbon so the engine clogs up and it runs like crap."
This seemed to confirm the rule I had learned earlier so I asked straight up "So is the keep her above 4000rpm rule a good way to keep the engine clean?" He said "Yes, you should keep the engine in the 4000rpm range and above to prevent carbon problems over time. If you look at all Porsche tachometers, 4000rpm is straight up to make it an easy reference point." I checked when I got home and sure enough the Boxster's tach has 4000rpm straight up too even though the tach goes to 1000rpm higher than the 928's tach.
So keep her above 4000 and she'll thank you for it every day. 