i cant speak to how it goes in a 300d but any ac system i have worked on at the shop we have just added about an oz. at the end. for example, in a Chevy silverado, i replaced the compressor and receiver drier, then once everything was back together, evacuated the air and charged the system. once the system was charged i fired up the car and using an oil pump which injected oil via the low side service valve. i injected about 1 oz. of oil, and the duct temps immediately dropped. i would recommend also adding a bottle of "ice 32" which is a lubrication enhancer. ive seen with my own eyes the 10 degree difference it makes at the vent. it works by lubricating the compressor and condenser, aiding in heat transfer and in the end dropping vent temperatures significantly.

i dont claim to be an expert, just sharing my experience.

best of luck, Jack