This is indeed true. The owner's manual of my C6 Z06 recommended exactly that before heading to the track.

 

plums,
you and I both must have graduated from a different mechanic school than the gentleman above. Oil pressure is produced by the oil pump and limited by the by-pass valve. Not even the deminimis additional head pressure at the sump caused by an extra 1cm of oil level will have any impact on the output pressure of the pump. The danger of a high oil level is moving parts whipping air into the oil causing oil pump cavitation, and subsequent loss of lubrication due to failing oil pressure.

 

The gentleman in question should follow his own advice and learn a little about how engines work.

 

That is true and I almost posted a confirmation
of that in response to a post yesterday. But,
I figured it would be pretty much understood.

In any case, at least the 4.0L V8 has a windage
tray as well as the structural sump to dampen
the whipping.

If the oil is really high then you move
into the territory of bent/cracked rods, wiped
bearings and other such trauma.

But that is not the case for an extra quart.

 

With that in mind, the slight overfill could be viewed as an
accidental favour performed by the various Jaguar techs that
have been flogged publicly here.

 

2016.04.28

2016.05.14

cough!