Anothe Oil Pressure Question

[Dave32]

Hi Guys,

Just wondering, my car has usually been run with a 10W40 oil, but on the weekend I chagned over to Mobil Fully Synth 5W30, aparantly this is what mobil recommend and it seems it gets some pretty good wraps.

Driving the car feels great, the engine feels alot smoother than before, however I've noticed after moving to the thinner oil, oil pressure has dropped quite a bit, it used to sit on about 1-2kg/cm3 on idle and 4kg at approx 4000rpm 6 at approx 4500 rpm, but now it sits at about 0.5kg/cm3 at idle and about 2-3 doing 4000rpm.

After listening to a few different people I also opted to give the engine the full 5L isntead of the specified 4.5L, so i am also running 500ml extra oil.

Question is should the oil presure be so low, and is it due to the thin oil? Does thinner oil lower oil pressure? and what does increasing the volume of oil do for pressure?

I've also read that the factory gauges are not very accurate, and it may just all be a dodgy sender, thing is it seems to be fairly consistent with readings so what should i do?

Another thing also, after approx 5000km should the engine oil be completely black? I have never changed the oil myself with the GTR but I have never seen oil come out that black on any other car even after 10,000km so is this a danger sign?

You thoughts will be much appreciated.

Cheers,

Dave

[SECURITY]

oil pressure will drop with thinner oil. people have used thin oil then used something like motul 15-40 and have noticed the oil pressure increase in all rev ranges, so yes, using a thinner oil will effect oil pressure.

increasing the volume of oil wont effect oil pressure. i've heard that over filling the oil in the 32 gtr's helps prevent the bearing spinning problem (dont quote me on that. if its gonna go, its gonna go!). just dont over fill it too much as it might create air pockets from the crank hitting the oil in the sump at a steeper angle. your pick-up could then 'suck in' a bit of air then cause you to spin a bearing.

my oil used to get pretty dark, though since the rebuild it doesnt get as dark, more of a browny colour. what i suggest is getting a compression and leakdown test done, that will tell you if its burnt fuel leaking past your rings into the oil (caused by worn rings), or if you just need to flush your motor.

to flush your motor get around 2-3 bottles of some decent oil. it doesnt have to be crash hot, just nothing too shitty (at the very least a semi-synthetic). also get some decent oil you plan to run for the next 5000km as well as a new oil filter.

- drain the old oil.

- pour the flushing oil in then take it for a good 10-20min drive (you should do it for 40-50km, but im impatient).

- repeat this till the oil comes out clean.

- replace your oil filter and then fill with your good oil.