Gasoline and Unleaded gasoline

Gasoline noun - A volatile flammable mixture of hydrocarbons (hexane and heptane and octane etc.) derived from petroleum; used mainly as a fuel in internal-combustion engines.

Unleaded gasoline and gasoline are semantically related. In some cases you can replace phrase "Unleaded gasoline" with "Gasoline", this terms are similar.

Unleaded gasoline noun - Gasoline that has not been treated with a lead compound.

Gasoline and unleaded gasoline are semantically related. You can use "Gasoline" instead a noun phrase "Unleaded gasoline".