Which oil?

fastandfurryous · Post by **fastandfurryous** » 12 May 2006, 10:22

The correct filter for this engine is the Peugeot/Citroen branded purflux unit. Others fit, but don't necessarily have the anti-drainback valve in them that the purflux one has. You can get it cheaply as a Motaquip VFL 427. (if memory serves)

One thing I often do to keep the engine internals as clean as I can, is to run the engine with just a couple of litres of oil in it (at idle, no more) for 5 minutes when doing an oil change. This works like a flushing oil, but is significantly cheaper. This rinses out a lot of the oil that doesn't drain when you do an oil change, and the new oil stays a lot cleaner for a lot longer.

mezuk04 · Post by **mezuk04** » 12 May 2006, 10:23

I use the Purflux ones!

LeeDJC · Post by **LeeDJC** » 12 May 2006, 10:26

I know when I used to have a Vauxhall with a 2 litre XE engine, long term use of a filter which didn't have a non-drainback would eventually cause damage to the head due to lack of oil on startup. Would this be the same on the XUD? I guess it would.

AndersDK · Post by **AndersDK** » 12 May 2006, 15:52

LeeDJC wrote:I know when I used to have a Vauxhall with a 2 litre XE engine, long term use of a filter which didn't have a non-drainback would eventually cause damage to the head due to lack of oil on startup. Would this be the same on the XUD? I guess it would.

No - not on XU engines.

Earlier XU's (BX petrols) have a cylindric gauze filter in the main oilway from block to head. This could certainly block if oil & filter changes were ignored.
This filter has been DIS-continued on later XU variants - so please dont worry.

But it still is a rather UN-fortunate engineering decision on the earlier XU variants - to say the least

MikeT · Post by **MikeT** » 02 Apr 2008, 12:43

I've mislaid my handbook and want to know what grade oil to buy. Last time it was a 15W I think but I've since read some interesting articles about engine oil efficiency and it looks like thinner oil is better.

Additionally, it seems the price varies greatly depending on the viscosity of the oil and as I aim to change it every 5K miles price is big issue to me. Any suggestions?

KP · Post by KP » 02 Apr 2008, 13:40

Im pretty sure its 10w40 that goes in mine when its serviced at either citroen or National.

If you could get 5w40 for summer use it would be better for the engine but you wouldnt notice much use and on an older looser engine it could do more harm than good really.

MikeT · Post by **MikeT** » 02 Apr 2008, 15:10

KP wrote:Im pretty sure its 10w40 that goes in mine when its serviced at either citroen or National.

If you could get 5w40 for summer use it would be better for the engine but you wouldnt notice much use and on an older looser engine it could do more harm than good really.

10W is the thickest I want to use, as you say, a 5W is probably better but I'm a little concerned why you think it could do harm? Surely it's the other way round where thicker oil is more harmful?

KP · Post by KP » 02 Apr 2008, 15:22

Any tiny imperfections in a seal that may leave a really tiny gap will soon let out an oil with a lower consistancy, ie turbo seals and the like.

It could be worth a try and if it doesnt use any of the oil then its all well and good

If yuor keeping the interval short as well at 5k then it should suffice as well.

my 5k services occur every 3-3.5 months at the minute so it soons gets flushed out with new stuff..

MikeT · Post by **MikeT** » 02 Apr 2008, 15:40

Oh right, I'm with you on gasket/seal leaks (though they should be repaired in a perfect world), I was worried about engine component wear/failure. Presently, this engine uses no oil whatsoever so a much thinner oil should give a good indication of how the engine has worn.

P.S. Anyone know what the difference is between Diesel and Petrol engine oils?

KP · Post by KP » 02 Apr 2008, 16:07

Diesel ones will pull and hold the soot particles in them IIRC and petrol ones wont do. Different chemical mix's iirc

AndersDK · Post by **AndersDK** » 02 Apr 2008, 16:41

UNLESS stated in owners workshop manual - dont ever use a thinner vicosity grade oil than stated.
I'm in line with KP here, that later synt low viscosity oils at best is waste of money, at worst is harmfull to an engine specified for a thicker viscosity grade oil.
Harmfull as you may see all kinds of oil leaks and thus a sudden unwanted increase in oil consumption - in an elderly engine with high mileage.

Think of the oil as an integrated part of the engine. You dont just replace any part in your engine with any other part NOT specified for your engine type - unless you fancy lottery with your motoring budget.

Instead go for the best/highest API spec on the correct viscosity grade oil for your engine.
The viscosity grade is the 10W40 number f.i. - which has to be pr your owners manual. You may choose mineral, synthetic or semisynt at your choice, but the xxWyy number MUST be as stated.
The API spec is the SF/CJ marking f.i. - which you are free to select after the highest possible alphabetic marking you can find. This is directly a measure for the QUALITY of the oil, i.e. the longevity and strenght of the oil.
You will notice that the pricetag directly follows the API spec.

MikeT · Post by **MikeT** » 02 Apr 2008, 17:33

Thanks for the advice. I'm aware of the specifications and that synthetics are, generally, wasteful but again I have to ask, what could be harmed by using a thinner than specified oil?

jeremy · Post by **jeremy** » 02 Apr 2008, 17:57

In an oil description (eg 15/40) the first figure is the viscosity when cold and the second is the viscosity when hot.

Which means that the cold bit only is relevant when starting and the hot bit is going to be the most important.

One reason for the very long life of the XUD engine is apparently due to its careful control of piston ring temperatures - which is presumably why my 206,000 mile TD BX seems to use slightly less oil than our 95,000 mile ZX 1.9D. Having been brought up on BMC cars I still find the lack of oil consumption amazing!

MikeT · Post by **MikeT** » 02 Apr 2008, 18:09

jeremy wrote:Which means that the cold bit only is relevant when starting and the hot bit is going to be the most important.

I may be wrong but my research suggests that practically any engine oil gives adequate protection when hot. I would have thought, considering most engine wear occurs at cold startup, that the opposite would be true?

Admittedly I have more reading to do but it's an insteresting subject!

As a side note, while working on my car, a neighbour's father was tutoring his (30-something) son on basic car maintenance, having just purchased a used car. When it came to the engine oil, which was low, the father asked son if he had any to which the son returned with a handy tin of 3-in1 asking "Will this do?" It was just too funny to laugh!!!

XantiaMan · Post by **XantiaMan** » 02 Apr 2008, 18:11

You want a 15w 40 oil except when its colder than 10c when i find a 10w 40 is better, if it was really cold you could get away with a 5w 40 but on anything over 100k its a waste of money and could potentially burn more depending on your engines condition.

My car is due a change shortly, its done 6000 miles, driven hard and i've only topped it up once, less than a litre of oil and its running 10w 40, now at 160k.