"How much oil pressure should an engine have?" That question has been around for a lot of years, and "Opinions are like 'noses'- - - - -everybody's got one and some of them are really smelly!" Theoretically, it's possible to lubricate an engine with ZERO oil pressure- - - - -as long as the oil pump supplies exactly the amount of oil every part in the engine gets adequately lubed. If the pump supplies one drop of oil to a bearing every time the same size drop falls back into the oil pan, the bearing will get lubed adequately, and the pressure will be zero. "Pressure" builds up because the pump is producing more oil than the engine really needs. Now, that's great in theory- - - - - -but how do we know that everything from the main bearings, to the rods, to the cam, to the valve lifters, rocker arms, etc. are all getting the exact amount of lubrication they need? Oil pumps are designed to supply adequate lubrication during the "worst case" scenario an engine is likely to encounter, plus a little fudge factor to offset any margin of error there might be under less than ideal operating conditions- - - - -bearing wear, fuel contamination, restricted oil filter media, etc. So- - - - -why not just design in some massive overkill- - - -several times the pump size that's actually needed, so there's no doubt that everything gets lubed? One drawback is the power required to drive the pump- - - - -parasitic losses due to friction, internal drag, and other factors can and do reduce the power necessary to actually push the vehicle down the road! Those internal power losses also increase fuel consumption- - - - -sometimes dramatically! The simplest way to assure adequate lubrication without a lot of parasitic loss is to design a pump that has a fair amount of overkill, volume-wise, and install a spring loaded pressure relief valve that shunts excess volume back to the oil pan once the desired lubrication gets done. If I could be sure that all the lubrication that an engine needs happens at 5 pounds of oil pressure, that would be an ideal situation- - - - -but to keep drivers from obsessing about possible engine failure, most manufacturers build in several times that number. It's also good to know that the average "idiot light" switch turns that little dash light on at around 7 PSI! That's one reason a lot of vehicles switched to warning lights over gauges- - - - -several decades ago!
Jerry
