Guys, thank you for all the speedy replies. I do not want to open yet another can of worms, but was it not the general consensus, synthetic makes these youngtimers weep at the seals? Ordinary 10W40 could be the answer to my ailment, but I am not sure, why the workshop recommendation is for such a high viscosity oil, might it be higher initial pressure requirements?
Johnny - although I am sure the Advantec oil is a fine one, but isn't it a synthetic one? I would much rather change a good quality mineral oil on a more frequent basis, than buy something really spiffy and have leaks as a result...
Mlytle, Laitch - I did check, and 20W50 seemed to be the one, that has got the best characteristic all across the spectrum. It might not be after all, as winter commute is hard on the engine, and I am sure, 20W oil is thick as molasses in sub-zero temps
Chaos - You own a Ural? Blimey, I did not know, it was exported outside the iron curtain, let alone to the US :)
Other thing - would it be OK to drain the oil now, store it, and use it again once the weather warms up? I have driven probably 2-300 miles with this oil, and I would hate to get rid of it. Obviously if you say it goes acidic, or whatever whilst stored I'd chuck it away...