I never heard of this in 76. I can remember what I used in my 73 Grand Prix though, it was uniflow later change to superflow by Exxon Mobile. Do you know about the price of syn in those years? I remember cy change interval too, it was 4000 miles. I had about 125 thousand miles on the car when I got rid of it, a lifter colapsed and I thought I need another car but it was a big gas hog anyway. But all in all I am glad of the syn oils and these day it isn't a debate with the tests we have access to.....later teddy