[woofhaven]

10W30 oil is 10W weight oil, with polymer additives to make it behave like 30 weight oil at 100 degrees C. When the oil undergoes thermal breakdown, two things can occur. One is the breakdown of the polymers, so that the oil always behaves like 10W weight oil. The other is thermal breakdown of the base 10W weight oil itself, resulting in an even thinner oil. Bottom line -- thermal breakdown = thinner oil.

None of this should be happening to an appreciable extent in 2000 miles after an oil change. You've got something funky going on. I would try running you car without the Lucas additive and see what happens. Some research has shown that oil additives (including Lucas) can have unpredictable results when they combine with the engine oil.