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MG MGF Technical - The dreaded mayonnaise on the dip stick

Hi Guys,

I noticed a beige coloured substance mixed in with the oil on the dipstick when I checked the oil level at the weekend.

I remember reading before this is where the oil and engine coolant have started to mix, and an early sign of a HGF.

Am I in danger of having a HGF soon? I haven't noticed any of the usual signs mentioned on this BBS yet. My car is due for its second service soon, so I'm going to ask them to check it out, just to be sure.

Hopefully I'm just being paranoid. Any comments are welcome.


Daniel Ginger

I have exactly the same situation: that bright coloured emulsion right above the current oil level of the dipstick. I have it since *months* now, no severe other problems (ok: loss of oil due to leaking camshaft oil seal). The color of the oil itself (and the coolant fluid in the expansion) seems ok for me. I'm a bit unnerved because of this emulsion, too. But haven't planned certain actions until it get's worse.


Hi Markus,

Thanks, you've settled my mind a little. I'm going to see what the dealer says at the next service anyway, just to cover my backside. The car is still under extended warranty. The coolant level is still okay, which is a good sign.



Daniel Ginger

The 'mayonnaise' emulsion in the sump is just an indication of excessive moisture. If you regularly do short trips then the oil doesn't warm up properly, and the moisture level will be increasing over time. Once this happens, I would change the oil and filter; then run it for a couple of weeks, warming the car fully after each start and see what happens.


Thanks Steve,

I think you may have hit the nail on the head. I travel less than two miles to work each day. That will be quite a build up in moisture since last march when the last service was done! It is my own fault for being lazy and not biking to work.


Daniel Ginger

Noticed this months ago and its now gone - no HGF. Does fully synthetic oil emulsify as I'm due an oil change and it might be worth the extra money to avoid this.
Nathan Carnie


I've noticed the same kind of deposits with my F with the same kind of daily use - once side of Hemel to other (to-from work). Initially this concerned me, but I felt less so when I opened up the engine bay and removed the 'proper' oil cap - no traces in there, clean as it should be.
Paul Lathwell

A switch to a Fully Synthetic oil or more Frequent Oil
and Filter Changes would be wise if your MG is used
for mainly Short Journeys.

I've noticed the same problem on my car today and I also do mostly short trips. The problem I have is, I don't want to change the oil, as this was done only a month ago.

Localised emuslification around the dipstick tube is to be expoected as you have a steel tube that has a lrge surface area to dissipate heat. Even with a warm engine bay you get the temp of the internal crankcase gasses, which contains water vapour, much hotter than the air temp in the engine bay.

The result is that water condenses on the inner walls of this steel tube and then mixes with oil particles to creat the characteristic emulsification. As this is not a serious problem there has not been the need to lag this with insulation as is the case on many FWD applications.

Short journeys simply aggravates the problem since it allows the creation and build up of this. If the car was used for more longer runs periodically then the much higher temps reached would naturally purge this emulsification.

Remember too that the water content of the atmosphere is somewhat like the ground at the moment - sodden. This too adds to the problem.

Semi and full synthetic oils are mre resistant to emuslification and this may well assist the owner whose journeys are short. It is also a fact that a car used only for short journeys will benefit significantly from an intermediate oil and filterchange at the halfway interval between the sheduled annual services.

Roger Parker

This thread was discussed between 05/02/2001 and 11/02/2001

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