If for whatever reason the oil didn't get to lubricate internal engine parts they can wear out from new in just a minute - it's not a joke! Letting an oil change go too long is not so harmful so fast. Think of like a nice sharpened pair of ice skates that when only used on nice clean ice can stay sharp indefinately but just one run (like a foot) across cement or something they are trashed. The skates can be resharpened fairly easily. Your engine can be reworked (rebuilt) but it will never be close to as good as the original.
You said it used some oil and that alone suggests neglect. Some much older cars routinely used some oil but that isn't the case anymore.
You might squeeze out some more life by getting the oil pressure back up to par and don't let it get low. When it says to add a quart that's the maximum amount low it should ever have to tolerate. Don't wait for a light to tell you it needs oil as most are inaccurate and many are just TOO LATE lights.
The cost to repair that damage is staggering. The best of the best isn't as good as the original. Oil has nothing to do with the belts and other parts that are not lubricated by it. Some parts can get worn and effectively be replaced but the general neglect will show up and haunt the engine forever.
All the harping about oil changing and qualities of oil is not a joke. It really works to take care of them. Oil is the most important thing for your engine. Get it diagnosed as to how far it has been damaged fix that if practical and if you take care of it you might get more life out of it. I have acquired many cars that were neglected and if not too bad, with taking care of them from then on they got no worse and some improved. Those were all tolerant old American style cast iron engines that could tolerate more abuse back when. Virtually all newer engines don't tolerate poor lubrication from any cause as well but do just fine with care,
T
Tom Greenleaf - MetroWest Boston - USA
_________________________________________
http://www.autoacsystems.com/tomgreenleaf/