hi there why would a gallon of dino 20w50 have a sticker saying 'should not be used on a post 1980 vehicle'. is this because a) it's not up to the job (however short the oil change) b) they want you to buy the synth's and semi-synth's on the next shelf. c) none of the above. i bought this to top up my 1989 mercedes 300te with 185k and my daewoo matiz with 55k. the merc does a couple of 300mile journies each month and the daewoo is a city car. cheers sebastian.