Engine Mechanical problem
2005 Subaru Outback 4 cyl All Wheel Drive Automatic 67,000 miles

While driving home from the airport I started hearing a loud noise like a siren and then the "Check Engine Light" came on and the "Cruise Control Light" started flashing. I had it towed into the dealer the next day and after a couple of days they called back and said it had a bad turbo charger. I told them them I had missed the last oil change and had about 8000 mile on this oil. I always made sure the oil level was correct. They said the turbo failure was due to not changing the oil and that small particles clogged the passageways. After paying $2100 to have a new turbo installed and only getting five mile from the dealership the "Check Engine Light" came on and the "Cruise Control Light" started flashing again. I had it towed back to the to the dealership and upon inspection they now told me that some tubes that go to the camshaft were clogged and needed to be replace for another $400. I have not got the car back yet to see if that has resolved the problem.

I have read article that have stated that you should be able to go 7500 miles before changing the oil with no problems. Making sure that the oil level is correct.

My question is: Would not changing the oil for 8000 mile cause this much damage?

Thanks