Related Clues:
- Manuscript encl
- NAPA buy
- Gas-tank additive
- 500 initials
- Auto engine additive
- Longtime sponsor in NASCAR events
- Popular fuel additive brand
- Auto additive letters
- Short return always comes back to you
- Big inits. in fuel additives
- Auto oil additive
- Major NASCAR sponsor
- Freelancer's encl
- "5W-30" preceder
- Logo seen on race cars