noise when oil level drops

My disco 300tdi made a horrible metallic grating/spinning noise when accelerating (usually worse in 4th) however I changed the oil a few weeks ago and was pleasantly surprised that the noise disappeared! Unfortunately however after a couple of days the noise came back, I checked the oil level and topped it up to Max on the dipstick and hey presto the noise disappeared again.

Now being a Land Rover the disco leaks a little oil here and there, so when the level drops the noise comes back, I top it up and all is quiet again. I can understand this if the level was dropping to 'Min' and would expect some friction type noise but we are talking a very slight drop from 'Max' ?

Can anyone shed any light on this as I can't be topping the oil up by a few spoonfuls every other day which is what it seems to need!

Cheers.

Assuming oil level is dropping only a little as you sau, I'm guessing that every time you add even a small amount of oil you are lubricating the top of the engine that perhaps isn't getting enough lubrication in normal running.?
What oil are you using? straight oil, or have you added any additives.?
Servicing....how bad was the old oil? has it had regular servicing?

Yeah that's exactly what it's like, as if you are oiling the top part until it wears off. I'm using 15w 40 mineral oil, no additives. When I got the disco it had been serviced but didn't have any service history so I can't say if it had been serviced regularly or not. Since I bought it I've changed all service items plus quite a bit more.

I was thinking about changing the oil again but this time using a flushing additive first?