My 560SEL is running R134 and is acceptable in the Las Vegas oven period (summer) only because I removed the engine fan and put in a dual electric fan setup on the radiator. That made a significant difference.

One of my SECs and a friends 560SL are running R12 and I keep them cool by using R290 (propane!) as the topping off refrigerant. When those two cars get a little low on refrigerant and don't cool acceptably well, I add a little R290. R290, as y'all know, is used in Japan and the EU as an automotive refrigerant, and is MORE efficient than R12, plus is completely compatible with R12 seals and lubricants. It costs me around $2.00/Lb at the local hardware store.

Be Cool,
Mike R.

__________________
There is a very fine line between "hobby" and "mental illness."
FrankenBenz: '87 560SEC with an '02 cammed LS6 and custom 4L60E.
Bling: '87 560SEC, ported/polished, lowered
Lisa: '87 560SEL, lowered