there's not really good chart to use, because the data mostly sucks. i had used a nice Brookfield rheometer ($20K) to gather this data, and i was fairly disappointed. here are general conclusions for a few popular oils.

trinity is lightest and linear in steps
assoc and losi are similar and linear in steps
hudy/serpent is generally heavier and exponential in steps

all of the oils tested exibited crappy qc. we had some oils that were out of place in nearly every brand, eg.: 60 > 70.

my advice is to copy the brand on the setup, or if you are doing all your own tuning, get a few bottles of each weight and combine them. that way you will have enough of the same silicone oil for the life of the car.

- jr levitz -