RPM Motor Oil and Lubricants porcelain sign features the RPM red circle. Measuring 8″ by 4″, this porcelain is in excellent condition! Whether you are displaying this sign as part of your collection in your man cave, shop, bar, or garage, or giving it as a gift, you can also browse my other auctions for more vintage gas, oil, aviation, automobile, motorcycle, and hunting signs. Vintage RPM Motor Oil porcelain sign. Bright colors w/ porcelain on both sides.