any recommendations for such as molyslip, slick 50 ect.......... for use in a diesel engine, what about gearbox ones too ? any good ?

Not a good idea while engine oil additives are mostly pretty harmless except for the ones that turn the oil into thick goo but I would advise steering clear of additives except for adding a flush agent immediately before an oil change.

There are a couple of exceptions to deal with specific problems additives to free sticking hydraulic tappets and also stop leak type additives the latter however only really work well on older classic cars which use a higher percentage natural rubber in the oil seals.


Molyslip type additives are particulate and most of the additive gets caught in the oil filter. Also Molyslip type additives should never be used in gear boxes they reduce the efficiency of the synchromesh and can cause problems for roller and needle roller bearings.



[Edited on 17/3/06 by britishtrident]

[Edited on 17/3/06 by britishtrident]

Jon

Have a read of this

http://www.fordscorpio.co.uk/snakeoil.htm

Cheers

Mark

Some manufacturers even advise against using flushing agents in diesels. I think if you think the oil's a problem just change it. If you get it good and hot there won't be much of the old stuff left.

Thing about flushing agents is to use them from the first oil change onwards, don't stick them in a 100,000 mile engine and not expect not to losen excessive ammounts of sludge.

thanks guys, I have no concerns about the engine just pondering if i would see any benefit from using anything in there, what about the gearbox, worth it in there ?

TBH you are probably better off just buying good quality oils in the first place rather than relying on any aftermarket additives. The oil companies know what they are doing (in theory at least).

The thing with diesels is you must keep up with their oil changes because the oil gets full of crap very quickly. As long as the oils changed at the correct interval and replaced with a quality oil then it will be fine.

David