Related Clues:
- Indy initials
- NASCAR-sponsoring additive
- Onetime sponsor of Richard Petty and Mario Andretti
- Encl. with some contest entries
- Winter Maintenance Formula maker
- Motor mechanics' org.
- Letters at Indy
- MS enclosure
- Logo on many a Richard Petty race car
- Motor oil brand
- Reply facilitator, w/o the stamp
- Indy supplement
- Auto additives co. that hints at this puzzle's theme
- Son of a Gun! Protectant maker
- Letters in a red oval