Here's my thoughts on the subject
Not being able to remember the shape of the Sierra DOC sump it is difficult to estimate the reduced volume of oil ( Photo would help )
If I take the 25mm reduced from my CVH sump as an example.
My logic is this.
Not actually reduced the sump oil level, just the depth of oil & the amount available.
In my case I have extended the deeper part of the sump forward to regain some of the lost capacity.
Dipsticks are marked with a max & min level, usualy about 20mm apart.
The engine manufacturer would have set the minimum oil level at a very safe margin to warrant that the engine will continue to perform in all conditions.
Most cars that have come to me with the customer saying " when cornering the oil light comes on " .
When the oil level is checked it is barely visible on the dipstick.
In an ideal world the solution would be to extend the sump a little to make up for lost capacity.
Provided the sump is well baffleld & there is enough oil available to the oil pump in all conditions an oil cooler may be of some benefit in so much as it will cool the reduced volume of oil available.
Lubrication of the main & big end bearings is provided via the crankshaft. The crankshaft is drilled at each journal, oil is fed direct from the oil pump, through the crankshaft & onto the bearings providing lubrication.
This is why it is possible to use a dry sump set up.
Early in the morning, so hope it make some sense
