Having worked in trade hardware for a while, I am always aware that fast-moving bulk items with lots of competition are often sold with litle margin (maybe 10%), while bits and pieces routinely have gross profit markups of 40% or 50%, sometimes even more. So 'specials' on oil are probably good, but as soon as you move into things like oil filters, watch out!
And depending on the boss's attitude, you might get a discount for the asking, or just get knocked back.
