BMW: Convertible Storage, bmw engine, bmw service

Question
Micah,

Thanks a TON for the quick response and sharing your knowledge on my question. Your feedback has been very helpful.

Just out of curiosity, how long do you think it would take before acids/rust would damage the cylendar walls, and other BMW engine parts, to the point that the engine would need major repairs? Is a little acid/rust residue in an engine considered normal?

Thanks Again,
Eric
-------------------------
Followup To
Question -
Hello Micah,

I stumbled across this web and thought I'd give it a try....here it goes.

I have a 1997 BMW 328i convertible. I bought the car almost 4 years ago to this day. I really really like this car and try to take the best care possible with it. I only drive it during the warmer months and keep it garaged during the cold ones. Before storing the car for the first winter I had it, I asked for advice on how best to store the car (I felt that cars were never really menat to sit). I was told by a BMW service agent that if I start the car, let it run to operating temp. before shutting it off. They said don't run it for 5 minutes and then shut it off. They also explained the reasons why. Well, for four winters now, I have been running the car (not driving it) once a week till operating temp. to keep the parts moving (about 30 - 45 minutes). Someone this year has told me that I should not do that and just let the car sit until it's time to start dirving it. Okay, since having been told that I will change my storage habits but now what I want to know is what kind of damage have I caused to my engine. I've already heard about how air and gases mix in the cylendar chamber to create acids and that driving the car burns this stuff off.
What's your opinion on driving the car versus running the car during storage? Also, have my storage habits for the past four years been detrimental to my engine?
Any advice you can provide would be greatly appreciated.

F.Y.I. - I change the oil before it sits for the winter.

Thanks,
Eric
Answer -
This is a double edged sword. On the one side if you let it sit without starting the vehicle and letting it run to normal temp, the engine seals, belts, rings, and so many things can dry, or even sieze up. I have even seen valve springs that will stay collapsed after sitting, then break. On the other side of the sword you can allow hydrocarbons to build and cause issues, but this is rare. The acids you mention may cause issues, but the problems that running it without driving the vehicle are far less in my opinion than not starting it at all. I really don't think you have done any harm by starting it and would not change your habits. The reason you don't want to let it run for 5 minutes is because that is when the engine runs the richest (more fuel) and what fuel does not get burned will go past the rings and into the oil, and that can cause problems over time. Hope this has helped you.

Answer
Sorry it took so long to get back. I really don't think you have any worries. Drive the car and enjoy it. The thing I love the most about these vehicles is the fact that the drivetrain (engine, transmission, rear-end and ect.) are bullet proof. I have been working on these vehicles for about 20 years and you can count on one hand how many of the 6 cylinder engines and transmissions I have changed from a factory defect, and most of those were transmissions. The 8 cylinder engines had a run of bad luck there for a while, but they got that lined out real quick. I have replaced other engine in hte vehicles, but due to people thinking thier vehicle was a boat and tried running through water, hydrolocking the engine. So...keep away from large masses of water and you should be fine.