engine oil

[kermit the frog]

i change the oil in my bx regularly every 3000 miles and until recently i had a rather large oil leak which i managed to trace to the cam seal at the hp pump end.
i was about to do the oil change and a friend of mine said why dont you try some quantum oil from the volkswagen dealer he worked in.
(sorry about the mention of VW)

anyway i did try the quantum oil and believe it or not the oil leaks have reduced to a drip now and then rather than the usual puddle

i dont know what this oil has got in it but it must have something that revitalises the oil seals

i used to add half to three quarters of a litre a week now i add maybe that every two months its great and its not very much more expensive than CASTROL GTX

try it

[AndersDK]

Whats the viscosity index of the oil you used to pour in ?

- and the viscosity index of the famous Quantum oil ?

[AlanS]

I'd be having sleepless nights if this were me.

The only oils I know of which contain "seal swellers" are automatic transmission fluids, power steering fluids, (usually one and the same thing) and hydraulic fluids used in the telescopic forks on some modern motor bikes.
How they would go in a reciprocating engine is a mystery; might be OK but I wouldn't have been in it.


Alan S

[m_2975]

I would be having sleepless nights too!

The oil is most likely quite thick, whereas the original oil must have been very thin.


Stops petrol BX's burning oil to an extent too.

I use 15W50 Valvoline Dura Blend (Semi Synthetic). Works a treat on all BX engines and AFAIK they use less oil with it too. Probably the same with any thicker oil.


Michael

[wannab-x]

How does this oil business work, anyway? I've been told I've got slight valve oil seal problems, but that there are things to use which might slow the problem down & stop it from developing (1990 1.9 petrol engine). I've been putting in 20W50 recently - is this the most sensible oil to use?

Thanks.

[jeremy]

You'll probably have noticed that when certain chemicals come into contact with rubber - it swells. This is the theory of additive sealers - they simply make the seals swell up - whereupon they do their job again.

Try chucking some rubber components in cellulose thinners! I did it many years ago when I was overhauling someone's trailer brakes for them. Chucked them in a bath of the stuff - and next morning various covers which would have been very difficult to replace were about half as big again! - fortunately they returned to normal over the next couple of days!

[m_2975]

How does this oil business work, anyway? I've been told I've got slight valve oil seal problems, but that there are things to use which might slow the problem down & stop it from developing (1990 1.9 petrol engine). I've been putting in 20W50 recently - is this the most sensible oil to use?

Thanks.

The 20 stands for how much it has been refined. The lower the number the more refined the oil.

The 50 stands for the thickness. The lower the number the thinner the oil.

If a petrol BX is using oil it's usually from the valve stem seals. This means that it uses oil but doesn't smoke under harsh acceleration or heavy load. Commonly they don't smoke at startup either as the oil has usually subsided back to the sump beofre it seaps through the seals.

It's very uncommon (unless it's been over revved, never serviced or cooked) that the piston rings have worn or broken. This would make the engine smoke under harsh acceleration or heavy load.


I normally use a 15 grade oil because it's the recommended grade by Citroen. I used to use a 40 thickness oil in the BX but found that the 50 thickness resulted in less consumption due to it not seeping as easily past the stem seals.

For the BX engine i'd recommend AGAINST fully synthetic oil as the rings have been designed for pure mineral based oil. For a happy medium I use a synthetic blend as it gives you the prefection of synthetic and the body of the mineral.

Citroen in Australia have always recommended Valvoline engine oil. I'm not sure if it's available, otherwaise Pennzoil is second best for the BX IMHO.
Our cars have been running faultlessly on Valvoline from their first oil change and we've never needed to do the bottom end of any of them and the others have either done 120,000miles on the valve stem seals or never been changed (like in my GTI)!

Hope this clears things up.


Michael

[DavidRutherford]

The 20 stands for how much it has been refined. The lower the number the more refined the oil.

The 50 stands for the thickness. The lower the number the thinner the oil.

Are you sure about that...

My understanding is that the two figures relate to the fact that it's a multigrade oil, rather than a monograde oil.

SAE30 for instance is a monograde. There's a graph of it's viscosity relating to temperature.

SAE20w-50 however, is multigrade, IE it performs like an SAE20 oil in "winter conditions" (hence the w) and like an SAE50 oil when it's at running temperature. Thus, the graph of it's temperature-versus-viscosity looks like SAE20 at the cold end, and SAE50 at the hot end.

As proven by the comparison of 10w-40 standard oil and 10w-60 racing oil. Both are the same viscosity when "cold" (room temperature) but the 10w-60 stays more viscous at higher temperatures. (and hence is more tolerant of the very high temperatures seen in a racing engine)

Handily, Wikipedia agrees with me. As noted about halfway down this page

[AndersDK]

Modern sealing additives have nothing to do with rubber swellers ...
Its a lot more elaborated process that slowly seals up an engine from inside all over where the engine oil flows around.

Besides - how many rubber seals do you have inside an engine that would cause smoky exhaust because of leaks ?
Most seals are provided to avoid external leaks, i.e. dripping etc.
Valve stem seals are no more simple rubber seals. Its a couple of engine generations - including the BX engine range - ago rubber was abandoned here.

Ever heard about heat hardening plasticide ceramics ? Thats basically a rough explanation to how it works.

I've been using this modern additive stuff in my 19tri engine, which was a notorious blue smoker when it entered my BX herd. It really works like a small miracle now after some 1k km.
The exhaust smoke has gone - completely.

...

[DavidRutherford]

Valve stem seals are no more simple rubber seals. Its a couple of engine generations - including the BX engine range - ago rubber was abandoned here.

Are you saying that BX (XU/TU) engines don't have rubber stem seals? Certainly every single XU/TU engine I've ever stripped has rubber seals. In fact, ever single engine I've ever worked on ever has rubber valve stem seals. Granted, they're a modern form of hard rubber, but they are rubber none the less, with a small garter spring to hold the sealing surface as it wears.

Thus:


Also, This list of manufacturers of stem seals shows them all using elastomer (IE Rubber), or some blend of rubber/ptfe etc.

AFAIK all engine "stop smoke" additives are essentially seal sweller, and if used a lot will soften the seals so badly that they fail to work at all. If an oil seal leaks, there's only one thing to do. (well two I suppose; you could just ignore it.)

[AndersDK]

Right - I eat my own words again

I know I should not have brought up this issue

[DavidRutherford]

Right - I eat my own words again

Not at all... I'm only going from my own experience. If there IS an alternative to rubber valve stem seals then I'd be very interested to know about it, as I've never heard of anything but rubber, and can't find any other reference to anything but rubber.

... as it has to be said that rubber in a valve stem seal doesn't tend to last too well in the environment it's being asked to work in. The ones on the classic race engines we build at work go nice and crispy in no time at all.

[Baldbazza]

I put Quantum SL 15w40 in the GT a few weeks ago as GSF had run out of Total. The only difference I've noticed so far is that the engine's a bit quieter, but then you'd rather expect that from fresh oil...

[m_2975]

Allright, well i'll eat my words here too. My understanding was a little out.

I was on the right track though. The second number is the thickness when hot.

The first one just happens to be the thickness when cold.

The lower the cold thickness, the better at starting and lubricating when cold. Too low though and it will pass through the worn valve stem seals.

When it's hot something like a 50 doesn't pass through the seals as much.

[AlanS]

Have another feed of words then.

I would suggest that a few here would remember the lady with the BX which had done 565,000 miles that was originally a test car for a company developing long life oils over in the UK. The car was original right through and the whenever it was serviced, oils had to be sent back to the parent company for ongoing testing.
It began to use oil and the cause was put down as leaking valve stem seals. She approached the chemists/engineers at the company concerned who told her to go lighter grade.......lighter grade?
The theory was that if a lighter grade was used immediately upon finding that it was using oil, that this allowed the oil to drain off the valve stems and not slowly all drain down into the cylinders as heavier would tend to do. She reckoned it cured it.
I can't see it myself, but she had no reason to lie and was pretty switched on as regards cars.
As far as 1.9 petrol engines using oil is concerned; if it's the DFZ engine then better than even chance it could be stem seals but a DKZ, can quite easily be incorrectly fitted rings which aren't all that expensive to replace.
I spoke about it here:

http://www.bxclub.co.uk/forum/viewtopic ... 81&start=0


and since then there's been a few others who have come across the same phenomena. The engine spoken about is now running 10W40 semi synthetic oil and hasn't used a drop in over 4,000 klms. but I wouldn't recommend that thin a mix on an unknown high mileage engine.


Alan S