Engine whose fuel is a product other than a petroleum product

A fuel feed circuit for an internal combustion engine utilizing a carburettor adapted to receive as fuel a mixture in variable proportions of a conventional petroleum product and another product, preferably an alcohol based product, comprising a tank adapted to hold the fuel, pump means for delivering the fuel through first conduit means from said tank to said carburettor at a flow rate greater than the fuel consumption of the engine at full load, said carburettor including a fuel receiving float chamber, first means for returning fuel from said float chamber to said tank through second conduit means without flowing through said first conduit means during normal operations, said pump means, tank and the first and second conduit means defining a closed loop fluid circuit whereby fuel is continuously circulated through the tank, carburettor and the first and second conduit means during normal operations whereby local heating and separation of the fuel into its individual products is precluded, and second means for draining said float chamber into said second conduit means upon the deactivation of said pump means thereby preventing percolation of the alcohol based product.