BMW's although great cars, around 85-90,000 miles start having little problems. of course even little problems can cost a lot with these cars though. at that age of a BMW it is good to go and get a full tune up, and have all of the hoses checked and any leaks checked, as they are tell tail signs of problems to come. after doing a few routine replacements on BMW's with that many miles the car should run great up to about 140-160,000 miles where the same things could happen again. it is all in how you drive the car, where you drive it, and how fast you add the miles. as for James with the oil leak, first of all, the oil of a bmw should be changed every 3-4,000 miles because of how hot the engines run, and especially if you have a lead foot. if you have a leak, a common problem with oil leaks in BMW's is that the gaskets grow old and fall apart creating leaks, and crap in your oil. check your gaskets and flush the oil compartment several times with clean oil straining it every time in case of any clumps. hope this helps.
I bought my 525i SE Touring '94 in 1998. It had 78,000 miles on it. Initially, I had problems with leaking coolant that the dealer could not identify. After replacing the head gasket (which didn't solve the problem) we decided to use a tin of rad weld despite such a treatment not being recommended by BMW. The problem was solved and I'm still running the car in 2004 with 162,000 miles on it. This vehicle cost over £33k new and the secret has been to attend to problems regularly to avoid foibles getting out of control. Replaced entire exhaust system at about 130,000 miles incl. cat converter. Replaced all hydraulic lines at about 120,000 miles. I would budget about £1,000 a year to keep this baby trouble free. That's a lot cheaper than a year's leasing costs!