Its a common occurence on many types of engines. You can't say a blanket yes or no to this as it depends on many factors.....(a) air temperature & humidity (b) types of journey (short journeys = more condensation) (c) quality of engine oil (d) correct grade of thermostat (e) correct operation of cooling fan (f) frequency of oil changes
Some engines never really clear the mayo under the cap and an occasional wipe with kitchen towel is required (all part of good maintenance). If the head gasket is suspect there would be an obvious excess of mayo plus other major signs.

 

Cant say about other engines but yes on the clio..on my last car [clio D4F722 engine ] I tackled the dealer about this and was told its due to the fact that renault changed the rocker cover to plastic from a metal one..personally I gave him a funny look with him insisting its a fact..:crazy:

 

When I adjust the tappets on my daughters Clio the underside of the rocker cover was like jelly and so was the oil filler passage. I would , for piece of mind, remove it and give it a clean.

Kenny

 

Plastic rocker covers are less prone to condensation mayo build-up as there is less of a temperatrure difference. Metal covers tend to be cooler due to the metal conducting heat away more rapidly.

On the old Vauxhall engines it helped to put a shield or aluminium foil over their metal rocker boxes.

 

After a lengthy conversation ive heard many ... MANY things about the D4F Engine that i dont know whether to believe or not lol

The main point ive heard that slight sludge builds up under the oil cap.... and this is not linked to the head gasket as there will be no coolant loss but is a common thing with the D4F Engine and is simply moisture ?

anyone else heard this ?

Yes this is called emulsification, i.e. oil and water mixing together to make a white / yellow sludge, it's caused by condensation inside the rocker box / crankcase wherever, and is common with many different makes and types of engines. (Is not unique to the D4F.) Not normally harmful, however it is aggravated by frequent short journeys especially in cold weather, where the engine is not allowed enough time to get properly hot, which will boil out any moisture, and the brief warming and cooling just encourages further condensation to accumulate. (Just one of the reasons why people say short journeys are not good for your motor.) In that case car preferably needs a long drive occasionally, I like to do this in Winter time every couple of weeks or so, if I haven't been on any reasonably long distance trip in the meantime. Also makes sure battery is charged properly.

HTH.