Manual A/C in 240D cools very well. Had an independent A/C mechanic fill it with R12 and it worked as new(very cold air). But there was a small leak and the Freon slowly leaked. When I took the car to another mechanic to fix the leak he filled it with R134. It doesn't cool as well. The A/C mechanic told me MB's that originally came with Freon work better with Freon and that's why he stocks it for MB's only. If the system is working properly and has no leaks a fill up with Freon should last a long time. I guess it also depends on where you live. Where I live it gets pretty hot and the A/C better be working to its full capacity.