This past weekend I changed the oil in a 5.7 liter Hemi V8 with MDS and after putting in the required 7 quarts, I noticed the date stamp on the 5 quart jug of Pennzoil 5W-20 Platinum Synthetic I used (I used 1 five quart jug and 2 - 1 quart bottles) had a manufacture date of 18 months ago. This 5 quart jug was new and sealed and I just purchased it last week from the local car parts store. Is this oil still good? Also I need to change oil in an old Chevrolet small block V8 and I have a brand new 5 quart jug of Castrol GTX which I purchased two years ago and has a date stamp that appears to be a little over 2 years old - ( production code is "K200463 19:50 NH N00139"). Is this oil still good to use? It's been stored in a basement and it's sealed. Also in the past I accidently added 1 quart bottle of Mobil Fully Synthetic Oil to a vehicle, this bottle was sealed and in my garage. The vehicle ran fine and the oil was clear and appeared fine when I added it. The vehicle was run about 20 miles after the 1 quart of oil was added when I noticed the oil was 11 years old from the production stamp on the bottle when I threw out the bottle. I immediately changed the oil to new motor oil. How long can oil sit sealed in a container before it goes bad? Thanks in advance for your advice and comments.