Related Clues:

• Motor oil additive brand
• Letters at a Nascar race
• Pit stop stuff
• Crankcase additive
• Gasoline additive
• Havoline competitor
• NASCAR advertiser
• Indy sponsor
• Inits. at a gas station
• Engine-cleaning brand
• 500 letters?
• It's intoxicating
• Racer's sponsor
• Its slogan is 'The Racer's Edge'
• Fifth element