recently the oil pressure in my 884runner v6 has been fluctuating. when i'm going up a hill it's just over half on the gauge and as soon as i let off the gas it drops down to under 1/4 immediately. truck has been running fine. no loss of power. no overheating. not burning oil.

 

Toyota oil pressure gauge? put a manual gauge on it and see what that reads.

 

Oil pressure changes relative to engine speed and temperature.

The oil pump pumps a certain volume of oil per engine revolution. You can think of all the oil passages as a fixed restriction, (orifice if you will). as the oil volume increases with engine speed you are trying to cram more and more oil through that same little hole reulting in oil pressure increasing til the bypass vavle opens. As the oil gets hotter it gets thinner and becomes easier to push through that little hole so the pressure falls off some.

The factory guages are not particularly accurate and the senders get worse with age. so if you have any questions about the oil pressure then I would recomend connecting a good guage to it to see where it is, and use your dash guage as a reference to let you know when something is a-miss.

 

how much fluctuation is normal? Also if the engine is losing pressure, what are the possible causes? Thanks

 

Your original description of your oil pressure, up and down a hill, sounds normal to me.

You believe its behavior has changed. How do you remember it behaving before this?

 

there is normally quite a bit of fluctuation in oil pressure, probably as much as half the guage scale or so.

Things that cause a loss of oil pressure are; low oil level, incorrect oil viscosity/ eccessive oil temperature, restricted oil pickup, worn oil pump, bearings, crankshaft, camshaft, etc....

 

Mine does the same, but it's been going on for the past 20K miles without issue. This engine is getting ditched in 5 months so I'm not too worried about it.

 

I'm running 5w30 in my 3vze with 156,000 miles because I just had the headgaskets done and that's what they put in there. I noticed at idle my oil pressure is lower than it was before, I've been driving 200 miles like this and I plan on putting in 10w40 on Tuesday. But my question is will such a light oil hurt my engine in any way, the valves seem to tick louder now too, oh yeah I'm in Massachusetts. Any opinions would be appreciated.

 

I'd be surprised if your oil consumption doesn't go up. But shouldn't hurt anything. Most damage/wear is done right after startup, so a thin oil helps defeat that, particularly in cold weather.

For what its worth, I live in sunny california and have had excellent luck with 15w 40 (Rotella T). I use it in everything... diesel tractor, Rx7, new Honda Rincon ATV, honda generator.. etc. You will get different opinions on this whole subject, most of which has been covered exhaustively. Do a search if you want to read lots more.

Almost everyone will tell you that changing regularly is most important. I prefer the Shell Rotella T having switched way back because of anecdotal proof from 18 wheeler types.

 

Mine is around 15 at idle once it regular operating temp, and around 50 or so when im running in the normal (1500-4000) rpm range... Could go as high as 75 at times... i know its a different engine, but mine too does the same thing... if i let off the gas, its immediately goes down to 12-15 psi and when i press the throttle, back up to around 50 psi.