guys , I don't think Sinclair was the only one's to use H-C , I'll look in my papers and see , but I think it means HIGHGRADE-CRACKING, cracking was the name of a process used to make fuels, M-C = MEDIUM- CRACKING, L-C = LOWGRADE-CRACKING, when Sinclair started useing the H-C Houston was even a oil area , the only reason oil was brought to the refinneries in Houston was so the barges and ships didn't have to go around the horn at that time, later the Panama canel. then even later , theres a giant pipe line that runs from Houston to yes , Bakersfield and Long Beach. and from Long Beach refinneries to yep San Francisco right next to I-5 actully Coalinga. Getty oil put that pipe in durring the late 40 early 50ties into the 60ties, Texaco has that line now, if Bobby Lewis was around he would know, where is Bobby??? Armadillos might have got him , I seen one time a horny Armadillo jump a Volkswagon. yep . thats what I saw. or was it a worm from a Tequella bottle jump a tomatoe worm, I don't know one of them.