Good day to all!
I use a XJ6 motor from the 70s in my self built car, which weighs approximately half of the XJ6 and never sees much above 120 kph (give or take 3.000 rpm).
So I figured my operating temperature is a conservative 100°C (I know, I need to validate this). Since 10W40 lubricates better than 20W50 at lower oil temperature, I expected a benefit.
However, the oil pressure dropped from 40 psi to 30 psi at cruising speed. This does not have to be a bad thing, but I am curious.
The pressure values are also not validated (I read off the stock, 45-year old gauge), but the drop is a fact.
I have a few next steps, from replacing with 20W50 to reverse the effect, via an actual temperature check to fitting a calibrated pressure gauge.
But I am lazy and like to hear an opinion about the drop in psi.
Has anybody run their XK engine with 10W40 (or 0W40)?