Hi, all,

I recently lower the water/engine temp from 95C to 86C by changing to low temp thermostat and lower thermo fan kick-in temp. And I'm using Redline 10W40, the sensor is placed on top of crankcase(oem sensor location).

Before lower it, my oil pressure was:
At hot idle: 20 kpa
At wot: 70 kpa (maybe limited by regulator?)

Now, it's:
At hot idle:23 kpa
At wot: 75 kpa

My question is should I switch to thinner oil to avoid excessive engine wear? Maybe 5W30?

PS: Here is some redline oil viscosity data:
05W30: 67@40C 10.9@100C 3.8@150C
10W40: 98@40C 14.6@100C 4.7@150C
And for Castrol:
05W30: 72@40C 12.0@100C 3.6@150C
05W40: 84@40C 14.0@100C 3.8@150C

Thanks in advance

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MY08 STI 422whp at 1.5bar on E85, built by Diversion Garage, assembled and tuned by EvoR

Update from new owner: 375whp at 1.4bar on 98, at Tokyo Motorsport

Motor Oil 101

The best article on motor oil I know.

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[COLOR=Black]Liberty GT Spec B tuned 240 HP & 372 Nm at the hubs.[/COLOR] "Instead of banning high performance cars - ban low performance drivers"

Maybe I didn't read it properly, but I couldn't find what I want there.

I assume oil viscosity and temp are exponentially related? So even 10C lower could double the viscosity?

__________________
MY08 STI 422whp at 1.5bar on E85, built by Diversion Garage, assembled and tuned by EvoR

Update from new owner: 375whp at 1.4bar on 98, at Tokyo Motorsport

Thank you GTB, just notice in the article, he mentioned "use whatever it takes to get 75 PSI at 6,000 RPM". So I think I should keep using 10W40...

__________________
MY08 STI 422whp at 1.5bar on E85, built by Diversion Garage, assembled and tuned by EvoR

Update from new owner: 375whp at 1.4bar on 98, at Tokyo Motorsport