Originally Posted by Hit Man X

System capacity and lack of ability to remove heat from the system (condenser).

My 750iL is almost 4.3lbs of R12... best the W126 had was 2.9lbs. Significant difference.

'85+ W126s at least received a better condenser (tubes are smaller) and a bigger aux fan. Late 126s had dual aux fans. Also the size of the main cooling fan plays a big part into pulling air across the condenser too

Tint makes a world of difference too.

Stick with R12 on these cars or go the extra step to a parallel flow condenser if you plan to use an alternate refrigerants. I am actually curious how a parallel flow would work with R12.