How fast does oil circulate through an engine?

[SuperEd73]

Hello BITOG,

I was thinking about this yesterday on a whim and I figured I'd ask the BITOG world.

How quickly does oil make a complete cycle through an engine? What I mean is, if you could trace the same molecule, how quickly would it get from the pan, through the oil pickup, through the pump, up into the engine and then back into the pan for the next cycle? I'm sure it would vary on oil pressure/flow rates/viscosity/engine, etc, but I was wondering if there is any rule of thumb here?

Thanks!

Ed B.

 

[XPR]

It would depend on how fast the oil pump is turning.

 

[Schmoe]

and the temperature of the oil. I don't think you can collectively figure something like that out since most vehicles are splash lubed. Some of it gets pumped to the top, i.e. the heads, but most of the time the oil is used for keeping the crankshafts fully lubed.

 

[meep]

AND THE ENGINE TYPE.

My old chevy 283 had oil gently pulsing from the pushrods at idle. low flow rate. My 4.0 jeep has oil squirting every which way from the pushrods at idle. lots of oil moving there. The honda looks like a kid in a bathtub at idle... cute little oil splatters everywhere under the valve cover.

Just for fun, I'll modify the oil temp statement - here's why: As long as the pump relief is not in bypass, every mL of oil pumped from a positive displacement pump will make it through the engine, albeit at a higher pressure when cold. When in relief mode at cold start and moderate rpm's the pump relief valve will bypass the rest of the engine, and that's when cool oil temp results in a reduced flow rate.

Crank bearings are lubed primarily by pressurized oil flowing through journals in the crank. Pump to block, block to bearings, bearings to journals in crank, journal in rods to piston pin to cyl walls; block to cams; block to lifters, pushrods, valve train (OHV). Splash lube agitated by crank to cyl walls, OR pressurized squirters to pistons and cyl walls in some cars.

happy friday y'all

Mike

 

[3putter]

WOW !

Talk about a knowledgeable answer...I really learned something.
Thanks, Meep.

 

[XS650]

The answer to your question is the same as the answer to "What does the conga line at the old folks home smell like."

Depends.

The oil that gets pumped directly to the main bearings and rod big end bearings then gets flung out of the bearings goes back in the pan in a a very few seconds. The oil that gets pumped up to the top of the head and splashed around takes longer to drain back to the pan. If you want an idea how long...park your car and shut off the engine with the engine warmed up and start checking the oil level every 10 seconds. Then see how long it takes for the level on the dipstick to stop rising.

 

[Eddie]

+1 for XS650.

 

[Merkava_4]

I'm going to say about 5 gallons per minute on average.

 

[Gary Allan]

Quote:

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My old chevy 283 had oil gently pulsing from the pushrods at idle. low flow rate. My 4.0 jeep has oil squirting every which way from the pushrods at idle. lots of oil moving there. The honda looks like a kid in a bathtub at idle... cute little oil splatters everywhere under the valve cover.

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Oddly, my experience is exactly opposite. Every SBC I ever saw with the covers off had Niagara Falls at idle, and every I6 AMC/Jeep just bled out of the rockers at idle.

My HV oil pump on my 4.0 is rated @ 9 gpm at something like 3500 rpm. I think the OEM is 5gpm+/-.


I don't know, but I would think that 3 gpm would be generous at highway speeds in a pushrod engine.

 

[mechtech2]

Most of the oil to the bearings leaks out the sides, and back into the oil pan. Some stays it's course, and is routed to the cams, or whatever, where there is more leakage.
Much is simply splashed lubed, like the pistons and cam lobes.
So some oil is immediately returned to the sump, and some makes it through.
Every engine would be different, and hot/cold would change things a lot.
Kinda like certain squigly things used for procreatiion.