What's normal oil consumption?

[bobirving]

My 1991 420SEL (112,000 miles) consumes about 1 to 1.5 qts of oil per thousand miles. Is this normal? I'm keeping up with it, and have the oil changed every 3,000 mi. like all my cars. Use only Pennzoil or Castrol SAE 10W30 year round (no synthetic).

Great performance otherwise as far as I can tell. Several years ago, while my Mom owned it, the car sat in her garage for a year without being driven at all (in Los Angeles -- mild temperatures year-round). Could the period of non-use have been detrimental?

Thanks!

Bob
Charlotte, NC