Price is indeed a factor in buying oils for most budget conscious car owners. But I do agree in the large price difference of the two you mentioned. Even comparing the same brands: Shell Helix Diesel Super and the Shell Rimula X is peculiar. The Rimula X though cheaper then the Helix by almost 35 pesos has a higher spec (CH-4) than the CF rated Helix. I'm not sure what part of the Helix makes it more expensive. ;)