The Cheapest Easiest DIY Check Would Be The PCV (Positive Crankcase Ventilation) System. The Tubing Should Be Unrestricted Inside And You May Want To Consider Replacing The PCV Valve If It’s Easy And Inexpensive To Replace.
A restricted PCV system can cause both leaks and consumption. I really doubt this the problem, but it should be checked and hey, stranger things have happened.
Some folks are under the impression that these cars were susceptible to engine sludging more than some other vehicles. Others believe that engine sludge problems in these vehicles was caused by owner neglect. Frequent oil changes during the vehicle’s lifetime would go a long way in preventing this.
http://www.schleeter.com/oil-sludge.htm
CSA