As some of you know, I've been measuring the oil temperatures in my L67 (supercharged 3.8L V6) equipped Caprice. The engine is mounted longitudinally in the Holden range here, and thus has a different sump arrangement to the same one in the US. 100C+ after 10 or so minutes on the highways, 105-109 after a 20 minute run (highway revs are 2,000)...If I hold it in "2", that increases the revs to 4,000, and I can see temperatures of 120C+ after 10km on the highway, same light load throttle opening. Have seen 135C... at 110C, the viscosity of the Magnatec 5W30 GF5 was around 8.8cst, lower than 101's optimum 10, and another proponent's 12-3cst as an aside...at 136 it was 6cst...refilled with 5W40. These temperatures are during a run, pull over to the side, cut the engine and drop a type K thermocouple down into the dipstick hole, exactly where the oil is draining back from the bearings et. al...there's a BIG disparity between that measured temp and the IR gun on the sump. Last night found what the Oz V-6 sumps look like on the inside (outside, they are massive winged things), and Holden have gone to great lengths to ensure that the drainback oil is the oil that's picked up by the oil pump (and thus what my dispstick thermocouple picks). Holds about 5 litres. Came across this paper http://eprints.nottingham.ac.uk/13180/1/Thesis_JP.pdf That's a thesis on optimising fuel economy, to the tune of 6% gains, some of which could be gained by segregating the sump so that the "working" oil warms quicker. Maybe this was Holden't intent, have a smaller working volume (of 20W50) that warmed quickly, while still having a full 5L in reserve.