Back in the day there was only one option for coolant / inhibitor (OK two to be pedantic) - it was that green stuff (ethylene glycol?) that you bought concentrated and diluted with water to whatever spec the handbook said. And that other option was not to bother and just use water - dangerous come the winter or with one of those new-fangled alloy heads. In the motor factors the other day there was a choice of green, pink, or blue liquids - the whole subjects more confusing than snooker, especially since I've been told that you cannot mix the (new) pink stuff with the (old) green. This has come to front of mind since I've half drained the 505 and am now wondering should I 'convert' the coolant to the modern pink stuff? With the "cannot mix" scenario how rigorous is this? ie if I drain the block, refill - maybe run some flushing through on basis of age since last done, redrain, then go pink will that be sufficient (given that theoretically some diluted green from the heater matrix may still be floating around)? I'm assuming here there's some advantage to using the pink stuff since all 'modern' cars seem to run it?