Can/should synthetic oils be used in older Landys?

[DiscoMick]

Reading Pat Callinan's latest issue with a good article about the advantages of synthetic oils left an unanswered question - can/should synthetic oils be used in older 4WDs originally specified for mineral oils?
This must have been discussed before, but I did a quick search here and couldn't find an answer - apologies if I missed it and this is a repost. If this is in the wrong section please feel free to move it.
For example, instead of using a mineral-based 15W40 in my 300Tdi, would there be any advantages in using a similar synthetic oil? If so, which one would be correct? Are there any disadvantages?
Obviously, I'm quite happy using the mineral oil, and I would err on the side of caution and staying with what the manufacturer originally specified, but is there any reason to go synthetic? For example, would a synthetic give better performance while delaying the need for oil changes and reducing soot buildup?
I don't know much about the intricacies of this topic, so I'd be interested in hearing some words of wisdom, if you wouldn't mind.

[redrovertdi]

i use penrite hpr semi synthetic in my 300tdi and change every 5-6000ks, that engine is just over 50,000ks old, in the past i put mobil 1 in my 3.5 range rover and that engine got so rattly with in a week[synthetic cleans to well in an old engine] that it had to be rebuilt. In my view i would use a full sythetic oil on a new engine after running in but not on an older engine.

[DiscoMick]

That's interesting. Is it the age of the engine or the design that's important?

[d2dave]

Not an expert here but me personally I think it is a waste of money. I did a fair bit of research on oil when I purchased my Td5 and I have settled on a semi synthetic. This was after much discussion with "Rick 130" who is a bit of an oil guru.

It will be interesting on his take of you question, if he responds here.

[Hoges]

I am a fan of synthetic oils for modern engines with roller rockers etc and built to close tolerances. I am not a fan of synthetic oils for larger tolerance flat tappet engines where it has been shown that synthetic oils do not, as a rule, promote the rotation of lifters and pushrods as effectively as do good quality mineral oils for the simple reason that synthetics are a tad too slippery!

I know there are others with passionate views to the contrary who claim significant success with top brand named synthetics in their flat tappet engines... good luck to them.

The worst case I saw was the effect of a high cost synthetic in a Lycoming 6 cyl in a C-182 with less than 800 hrs of engine time since the previous rebuild and which required major work. A $$$ partial rebuild later and another 1000 hrs this time on a good quality mineral oil and the wear was minimal. In both cases the oil was changed regularly.

The Magnatec 15W-40W oil for diesel engines is probably as good as any.