Oil for a 2.5TD

I bought some oil online for an oil change on my 1989 90. The oil is 10w40 part synthetic.

However, I read somewhere that it should be 15w40 mineral oil.

The stuff I bought is here:

Engine Oil 10w40 - 5 Liters DELPHI - H5885 for your car lowest prices - Filtering / Oil / Oil change - Oils/Lubricants - Engine Oil - Engine Oil 10w40 - 5 Liters - H5885

Will this be ok? The Haynes manual states:

Multigrade engine oil, viscosity SAE 5W/30 to 25W/50, to RES.22.OL.PD-2, or CCMC PD-2, or better!

Also, I bought some Slick 50, as I always used to add this to my cars many years ago. Is Slick 50 ever used by Land Rover owners, as I didn't find anyone 'swearing by it'!

Yes, you really ought to use Mineral.

There's also a thread on Slick 50 on here somewhere. Mixed results IIRC. Have a search for it and you'll find.

10w 40 is ideal. Part or fully synthetic, it's what my local Major land rover garage use for 12j 19j 200tdi. 300's should be 15w 40 I believe..

If it's specified for turbo Diesel engines then it'll be fine. Won't make much difference between 10w40 and 15w40 on an old engine. Mine always got 10w40 heavy duty engine oil I had lying round the farm

Cheers guys. It doesn't sound as though it is too much to worry about then, so I will give it a go.