Oil pressure.. if your oil pressure suddenly drops it is normally that your pick-up is blocked. This leads to no oil getting to the top of the engine. Un-lubricated hot components will cease, then bang. Engine rebuild time. An oil pressure gauge can give a good indication of any potential issues arising. Also, hot oil gets thin and pressure falls. On trackdays for example, if temps get up to 150* the oil becomes very thin and it can be difficult to maintain decent pressure, hence aftermarket oil coolers.