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sorry if I refresh old theme , but I have same or simillar problem.
today I change the oil with 15w-40 .. befora it have 10-40. and the issue is same.
when I start the car it is imediatly 5bar , one minute later it start to drop on 3bar , than on 2 bar , and hot idle 1bar.
now i done one total rebulit on one aan engine and they oil pressure newer drop under 1.8bar.. newer.
now we have same oil.
and sometimes when I drive the pressure start to shaking ..
what can be a problem?
oil pump? oil injectors? bearings?
now is 3 years of total rebuilt, can bearings do that problem on 40 000km?
I know theres a mann racing oil filter which gives you aprx 0,5bar more oil pressure and takes about 0,5ltr more oil. I can post the part number the next time I`m in the workshop
assuming that the oil ratings and specs are equal a 15W40 would not be thicker than the 10W40 that you were using before, and therefore on a hot engine, it would still have the pressure dropping. once the stem seals start to wear or the piston rings, you need a thicker oil on hot engine to sustain the warm idle pressure, assuming that the oil pump and gauge are reading accurately. I would therefore try a 10W50 oil to see if there is an increase in the oil pressure.
as a comparison, my oil pump was healthy throughout the 100K kms, i was using 10W50 most of the kms, and on the hottest day (temp close to 90) and idle at 900rpm i had 2bar oil pressure.
If your idle is at 700ish rpm, then that can also give you a dropped oil pressure.
10w40 oil is designed to work at an average of 100celsius when warm. If you're engine runs at 110celsius you can use a w50 mix.
Putting that to the side. Things that cause low oil pressure the way you describe are as follows.
Blocked strainer on the oil pick up pipe. Usually from sludge after a blown headgasket or silicon from rocker cover or similar breaking away.
Worn mains bearings from overfueling and infrequent oil changes.
Alternativelly if the engine has always done this since new then most likely incorrect oio squirters, worn crank causing incorrect oil clearances or worn oil pump.
Worn rings, guides, stemseals will not drop pressure they will only cause smoking. Running a thicker oil will stop the smoking by filling the gap so to speak at the sacrifice of the ability of the oil to serve it's function in protecting the bearings as it doesn't get to the right operating temperature.
Worn rings, guides, stemseals will not drop pressure they will only cause smoking. Running a thicker oil will stop the smoking by filling the gap so to speak at the sacrifice of the ability of the oil to serve it's function in protecting the bearings as it doesn't get to the right operating temperature.
I want to just stress how important this is.
You guys are too obsessed with oil pressure. Oil pressure is all good and fine, but putting 20W60 into your car, and thinking it lubricates better than 5w40, because it has 0.5 bar more pressure is incorrect, and the reason to "why" is perfectly explained by JP.
as a reference though, i had been running 10W60 and 10W50 from day one after the original rebuild on the engine, and bearings looked like this after 100K kms
oil pressure due to idle being higher and engine running cooler was most of the times (esp while in the uk) at 2.5bar on warm idle. So some damage can be done, but its not a definite fact.
my engine had cylinder glazing, which may be because of various different reasons ranging from just use and kms, to poor breaking in technique(known), and i dont think its related to the thickness of the oil i used.
so.. you want to say that 1bar at hot idle is normal?
If I use 10-50 than it will be better?
or I have to change oil pump , oil injectors and bearings?
all bearing is almost new. the problem is that I don't remember how it was oil pressure when I rebuilt the engine. was it 1 bar or more..? I don't know.
today I try to find out where is the problem.. and I saw if I turn the lights ON , pressure drop for 0.5bar .. ha ha ha
than I take instrument closter out. put another one from my second audi 200 20v , and they shoes 1.7-1.9 bar at hot idle..
than I clean contact on oil pressure gauge, so now I had 1.5 bar at idle. I have to check all instrument closter, because I had doubt there is some cold joint.
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