National Geographic : 1936 Sep
But Less Margin of Safety Than Pennzoil Gives Motors! Do you put oil in your car and forget about it? Then don't take chances. Get Pennzoil, an oil you can trust! An exclusive refining process gives Pennz oil its amazing Tough Film, many times stronger than your motor ever needs. Result: Up to 50% savings on oil - an extra mile or two per gallon of gas - and as much as 90% Parachute cords are tested to support FIVE TONS. Yet Pennzoil provides a greater ratio of protection.S S than these cords give the lives of stunt jumpers. "Mention the Geographic-It identifies you."