The present invention relates to an internal combustion engine having an injector which functions as a a positive displacement pump and dispenses an amount of lubricant fixed for each and every operation of the injector. The fluid dispensed could be a lubricant delivered directly to crankshaft bearings, camshaft bearings, tappets or cylinder sleeve. Alternatively the fluid could be fuel, water or urea delivered to an exhaust system upstream of a catalytic converter. The injector can have a one-way valve with a valve element having a domed or conical surface for directing fluid flow across a sharp edge which induces turbulence in the fluid flow.