So what's the deal. Someone explain how this works. When I break my engines in I use like 5w-30 non syn oil.. Once I break them in I switch to my 15w-50 synthetic oil which is what I clearance my bearings for..

So how come oil pressure get's higher with thicker oil vs thinner oil? How does this work?

 

Its kinda like trying to sip with a straw as opposed to trying to sip some ... honey? The more dense material will require more force, which in turn will result in higher pressure? I may be wrong, but eh, i tried.

 

The drinking straw analogy is true for viscosity effects on suction through a fixed diameter orifice, but I think a better description of oil viscosity affects on oil pressure is this;

Engine oil pressure is a function of how much pressure the oil pump & relief valve put into the "system" (the engine's oil passages, galleries, bearings, etc) & the "leak down rate" within the system. Pump pressure output is relatively stable courtesy of the pressure relief valve, so pump pressure at a given RPM can be considered a constant. Because the primary cause of oil pressure loss inside the engine is bearing clearances, you would lose less pressure if the oil were thicker & wasnt able to squeeze out of your brearing clearances as easily or quickly.

It's a well known shade tree mechanic idea to "revive" sagging oil pressure with thicker oil, but at some point only a rebuild will restore oil pressure lost through enlarged bearing clearances as the engine wears.
There are downsides to using thicker oil too, like poor lubrication at start up, when the oil is so thick it has trouble even getting to the end of the tiny passages for things like rocker arms.

 

What he said...oh and also the reason if you have a car that gets a knock and dont want to fix it you can put thicker oil in it and sell it quickly before it dies (to a dealership of course since they are dishonest and deserve to be screwed over)

 

haha yea..i guess..a simple way of lookin at it..is kinda like what the guy who mentioned the straw..take a mouthful of water, and spit it through a straw..it doesent take much pressure for you to get it through the straw...now take a mouthful of honey or chocolate syrup (yuck), and try to blow it through the straw..i bet you'll bust a vein in your head trying to do it..its gonna take alot more pressure to get the thicker fluid through the straw..same theory for your motor