I've read many of the oil threads previously and decided to put 20w/50 Comma Classic oil in my 2.25 diesel.

Now I hadn't thought nuch more adout it since but I went to see my landy man who had a strong opinion that I should remove the 20w/50 and use 15w/40 - reason being that the 20w/50 is for petrol engines only and does not contain detergents, where as a dedicated 15/40 diesel oil would.

I'm a bit sat on the fence with this and the way I see it is that I am lead to believe the tollerances in all 2.25 engines (petrol or diesel) are better suited to thicker 20w/50 oil and potentially help compression BUT a 15w/40 diesel oil would prevent sludging but not necessarily be 'quite' as good at protecting as 20w/50.

I do approx 2000 miles a year at the most and would change the oil at least annually so it would get regular oil changes.

Not sure what to do really, any thoughts / opinions?

Sorry, but your landy man is incorrect. That is a good oil for your engine and ideal for your mileage. change it every 2-3000 miles and your engine will be fine with it.

That's a little reassuring to hear. I've had concerns that the breather may block etc in time.
Did they / do they make dedicated diesel engine oils in 20w/50 though? Having looked at the Castrol and Comma website, they only make reference to 20w/50 being appropriate for petrol engines.
I just wondered that whilst my manuals suggest 20w/50, which was the best in it's hay day, if there are better diesel oils with appropriate detergents now and it's worth the sacrifice of correct grade over anti-sludging formulas?

I always ran 2286 diesels on Super Tractor oil universal 20/40 , which was pretty much standard practice by farmers , (cheaper than duckhams 20/50 as well) , its a diesel detergent oil . JMHO

I use 20w/50 in mine,(S3 diesel) it's a multigrade I think, but it runs lovely, no smoke, happy as a pig.