just passed 50k and thinking if I should go redline D4 or D6 its my weekend car but I live in NY so its cold half the time.
I spoke with RedLine tech support about whether to go with D4 or D6, as I live in Phoenix and have to cope with the extreme heat (I went to D4 for better summer protection.) The difference in viscosity between the two is 10%, I probably wouldn't even notice a difference when it's cold. The D6 is a better viscosity match to the factory fluid, and in the colder states in winter, that 10% will make more of a difference. You might want to go with the D6.