Word forms: (regular plural) rich mixtures
(Automotive engineering: Fuels, oils, emissions, and other fluids) A rich mixture is a fuel/air mixture containing an excessive proportion of fuel.
⇒ A rich mixture may be desirable under certain operating conditions, such as when the engine is under
load. ⇒ A rich mixture provides enough fuel to use up all of the oxygen in the cylinder. ⇒ A rich mixture has too much gasoline and not enough air.
Collins English Dictionary. Copyright © HarperCollins Publishers