Transmission fluid

96 Bonneville SE--Had transmission serviced by Independent garage using BG transmission service program. Was told that this involved a complete change of fluid (not a flush) and the replacement fluid was Pennzoil synthetic. Are there any complications that could arise due to changing from regular trans fluid to the synthetic? Was having some of the trans problems common to this year and model Bonnie before the change. Some improvement noted but not much. Would it be appropriate to go back to the regular fluid? Would appreciate comments from anyone who has changed from regular trans fluid to synthetic.

Thanks to all--Tugboat Sailor ATF 91

Bad idea on higher-mileage transmissions. If you're already missing some friction material on your bands, the 'slicker' synthetic can further degrade your trans by not letting the remaining friction material grip....

i use valvoline Dexron III max life,,never syn. on a high milage trans..$.02