I recently scored three (3) 5-quart jugs of Mobil 1 0W20 Annual Protection for $10.00 each at Walmart. I also got a 5-quart jug of Rotella Gas / Truck 0W20 for $7.50. The Rotella jug has a lot date on it...fall of 2018. The Mobil 1 containers have no markings. How can I tell when this oil was made? Thanks!