hi, i am new to this forum because i recently bought a 1983 240d. it has 170k on it and according to my local mercedes wizard, seems to be pretty solid throughout. I usually do basic maintence myself, but had the shop do my first oil and filter. They told me that they always use quakerstate 5w-40 synthetic on thier diesels. The strange thing is that none of the local auto parts stores seem to carry it!! should i use something else? what about synthetic or not synthetic? The previous owner did not use synthetic.