I may purchase a '90 190E (see earlier post on: Reliability of '90 190E?) that has 134K miles on it. As I 'd like to keep the A/T operating for as long as possible, I'm considering using a synthetic ATF in the transmission. Anyone have experience with this or info on it? I'm also trying to decide on A/C system servicing: keep the R-12 or convert to R-134a. Automotive A/C only gets used occasionally during several (3-5) months out of the year in my area.