Some background to the question in the title:

Recently after some inspiration from the forum I modified the feedshaft clutch and turned town it's OD so that I could get more travel towards the chuck. Some days later I made a silly mistake and crashed the carriage into the chuck, in the process I stripped a couple of gears in the gearbox and twisted a shaft. This should have not happened had the feed shaft clutch worked, alas it did not! And guess whose fault was it? All mine, when I assembled it after I had it modified I failed to adjust it properly

I have now replaced the broken parts cleaned everything and put everything back. While at it I took the apron apart and cleaned the apron gearbox as well, the oil inside was more like treacle both 8n colour and consistency. I filled both gearboxes with Tellus 68 oil up to the sight glass, however I think this is low. Not sure if the gears touch the oil at all.

Thanks Jason, actually the oil I have is Tellus 27, the oil which came out of it was more like 68. I'll fill it up till the gear touch the oil, I don't think some extra oil is going to do any harm, it will compensate for the oil lost as it leaks just as much as my old series 3 did!

The headstock gearbox unfortunately does not have a drain in the bottom and is practically useless where it is, so the only way to drain it completely is either with a syringe or opening the gearbox (messy job!). The apron was almost empty, below the sight glass for sure. And it leaks badly, mostly from the feedshaft worm pinion shaft and some from the handwheel.

I cleaned and tried to seal the gearboxes as best I could, hopefully that will keep the oil in.

Thanks John, good idea. Filled both gearboxes, and put everything back. Also made sure the clutch is correctly adjusted and functions as intended as a couple of replacement gears cost me 130€