Did you guys know there is a dye in most engine oils? I did not know that. They put it in there so if some one tries to claim engine damage from their oil they can put a light on it and see if it was their oil.
So if you take apart your engine, and it is red, or blue or vermillion in the top end, you can be it is oil.
It explains why when I drained my Castrol GTX it is reddish tinge. The heat activates the dye.
Bob, Lifetime bike: '71 T120R, bought in '71 at Ken Heanes, England.
This is the first time I read about dye in engine oils. That does not mean it is not true. I know dyes were sometimes used in compressor oils in the reefer industry. The maintenance engineer could add some, so when oil circulates through the complete system with the refrigerant (and it allways does), it will tell where there is a leak. It is not used very frequently though as there are better leak detection systems.
A britbike does not need a leak detection system. It creates it's own dye (black as my soles) and is in itself, by design, one complete leak detector.
I put a couple of drops of UV aircon dye in my gearox oil, you DO only need a couple of drops, leaks show up easily under a UV tube. I can't imagine a couple of mL in the engine oil will cause any harm, especially if you are going to change it after you have done the work to cure the leak