Used oil can pollute the environment and should never be poured down the drain. In many markets it is also illegal to do this.

If you simply keep on topping up your oil, you put more stress on the older oil that remains in the engine. And this stress issue has become worse in recent years as lighter, modern engines now run with about 25% less oil in their sumps. Shell Helix oil has a powerful ability to clean up your engine components and goes on keeping engines clean through to the next oil change.