[Dr Dave]

Originally Posted by rovers_andy

Bad idea, the sample won't give a true representation of Oil quality.

Ah, yes.......very good point.

[MrPogle]

Originally Posted by Dr Dave

Ah, yes.......very good point.

I am not sure why this is the case but am not disputing it.

If I took half the sample from the clean side of the filter and half from the dirty side, would that compensate for the issue?

[Dr Dave]

You won't get the choice when you remove the filter.

A small drop out of the sump plug would be best imo.

[doughboy]

Interesting about the UV, asked by brother who is a Race mechanic, and he's never heard of that, but they change the oil every few hundred miles tops!

I have to admit my only 'test' in 25 years of changing petrol engine oil is looking at and sniffing it.

By frequent changing I hope to get it still partially clear and not smelling to much of fuel or burnt oil.

Regular 6k is noticeably more like that than the rancid stinky black stuff you get out after 18k.

But yes, mainly for personal satisfaction....

[doughboy]

Originally Posted by Dr Dave

You won't get the choice when you remove the filter.

A small drop out of the sump plug would be best imo.

I would let a cup full out via the loose sump plug, then another clean cup full for sampling, that way you'll be into the main sump oil, not just getting bits from the sump plug thread! Wipe the sump plug first too.

That's how we take power transformer oil samples at work, we always use two containers, one to flush through the sample petcock, and a second one to catch the clean sample for analysis.

You can always put he excess back in the top!

[Dr Dave]

Originally Posted by MrPogle

My mate changes his oil in almost total darkness because he believes that even very brief exposure to UV light damages synthetic oil. This is why it is manufactured in UV-free facilities and packed in containers which block UV light. He is a forensic chemist so maybe he is right or maybe he is mental.

I might start my own tyre-religion instead.....

BMW only recommend changing your tyres at 2mm to keep costs down for fleet operators. 2mm is nowhere near enough tread for high-performance, enthusiastic motoring so I change my tyres at 5mm.

Interesting thing about UV.......

Can I buy your old tyres at 5mm please?

[Robin330i]

17000 miles is ok with modern good quality oils.

The reason why I know is because I deal with oil samples for our durability cars at work (I'm an engine development engineer at a luxury car brand in Crewe.......) - the oil sample results I get back for similar mileages show that oil viscosity is still acceptable and lubrication properties are still high enough for component protection.

[MrPogle]

Originally Posted by Dr Dave

Interesting thing about UV.......

Can I buy your old tyres at 5mm please?

It's interesting that my 50% worn tyres are marketable but Doughboy's 35% worn oil isn't

[MrPogle]

Originally Posted by Robin330i

17000 miles is ok with modern good quality oils.

The reason why I know is because I deal with oil samples for our durability cars at work (I'm an engine development engineer at a luxury car brand in Crewe.......) - the oil sample results I get back for similar mileages show that oil viscosity is still acceptable and lubrication properties are still high enough for component protection.

That's not going to be a popular opinion. Not least because it's more than just an opinion

My "research" so far does seem to suggest that expensive synthetic oils are superior not in the amount of protection they offer but in how long they can do it for. So if you are running frequent changes you may as well save the money and use cheaper oil (warranty issues aside). Basically, if you are going to drink 4 cans of beer and throw away the rest, the 6-pack is a better buy than the 12-pack.

[A_P]

Yea but no offence but hasnt this been extensively done already I remember reading about someone who who a two page write up after sending samples away. His point was changing oil in between services is pointless. The oil still works as it should for 15k for example.

It concluded with yes it was unnecessary on a modern car. Yet someone people would still do out of habit. I do it because my car is over 100bhp per ton NA engine. Therefore being less refined and more highly strung it gives me piece of mind.

Your whole basis for an argument is. Regardless of whether you can afford to fly first class for regular business trips. You should always fly economy.

Regards.

[rovers_andy]

Originally Posted by MrPogle

I am not sure why this is the case but am not disputing it.

If I took half the sample from the clean side of the filter and half from the dirty side, would that compensate for the issue?

Its not so simple, when you remove the filter and pour the oil out it will mix.

You could try and use a syringe to remove some of the "clean" oil but its not reccommended practise.

It doesn't help the O.P but at work the engines have sample points after they have been through the engine but before they pass through the L.O Cooler

[Robin330i]

Manufacturers spend millions and millions on engine durability dyno testing alone and the test we go through can never be simulated in a car - even on a race track all day long you will not replicate what we do on the testbed. The tests will include oil changes at the same frequency as what is reccomended in the hand book - if a problem is found on engine components due to the oil quality then it will be rectified with either a new grade of oil or shorter service intervals which will then be listed in the handbook.

There is no harm in having more regular oil changes however I can confirm it isn't required unless you suspect that you have a leaking injector ( fuel in the oil will heavily influence the oil viscosity) or if you do a large number of cold starts (-10'c) as fuel dilution in the oil will be greater.

[MrPogle]

Originally Posted by A_P

Your whole basis for an argument is. Regardless of whether you can afford to fly first class for regular business trips. You should always fly economy.

Regards.

No, it's more like if you want to fly business-class to New York, you may as well buy a business-class ticket to New York. Buying a business-class ticket to Los Angeles (via New York) and getting off in New York doesn't actually get you anything.

[A_P]

That is a pretty dire. Lol I don't agree with that.

But what I am interested in is exactly what your theory is? I was under the impression that changing oil too frequently is detrimental in the sense of the oil doesn't have long enough to break in and bind to compenents to provide protection. The point the guy made was, by the time the oil actually starts working properly then you change it out and then its pointless. It was over on the u.s side of the forum. He ran tests and had conclusive evidence that the oil changes in between were pointless.

But then again its difficult to put into a template for everyone. I may triple your miles. You may do triple mine. So in 6k someone could have lasted only 2 months or a whole year.

I had the 330i e90 for 4 years. And change oil in between services and change plugs even at oil service. But my was driven hard and used a performance car as u put it rather than a town cruiser. It ran like smooth as butter.

Would it have ran as smooth if I stuck to manufacturer schedule? Probably. But bmw messed up with run flats and cracking alloys. Hydro bushes and one thefts. So why should I trust anything they say?

The point is they have schedules for everyone. That's the guy who tracks the car and they guy who got a car from work as a repmobile. My car is not driven like his. Nor should I service it like him.

Your comment about using cheaper oil for frequently is also ridiculous. In which case then do not buy premium tyres just budgets. And enjoy.

I think I will continue to in between oil changes and premium tyres mate.

[MrPogle]

Originally Posted by A_P

Your comment about using cheaper oil for frequently is also ridiculous. In which case then do not buy premium tyres just budgets. And enjoy.

I think I will continue to in between oil changes and premium tyres mate.

You misunderstood my point.

Premium tyres are not long-lasting versions of budget tyres. They are better in all kinds of other ways. There is some evidence that expensive long-life oils are only "better" than standard-life oils in that they last longer. If this is actually true, then they are only worth buying if you make use of the extra life.

The issue about hard/gentle use is supposed to be addressed by the CBS system but I accept that this can only be so smart.

TBH I expect I will spend the extra and do inter-service oil changes because I do the equivalent in many other aspects of my life.

[A_P]

Yea but mate. You wouldn't need to swap out the oil in between services. You would be totally fine going on cbs. I see what your saying you want to know wether its totally worth it or for the extra cost.

Lets say its not. ... Your friend will still change very frequently. Especially when its free. I am not sure about the whole changing oil in the dark thing, but then again I have no knowledge of uv exposure.

So did you manage to get the oil out for a sample?

[MrPogle]

Originally Posted by A_P

So did you manage to get the oil out for a sample?

Ironically, I have decided to change the oil and take a sample from the drained oil .

Getting a sample is too hard as the oil cap doesn't provide enough access and the general consensus is that oil from the filter-housing will be unrepresentative.

Thanks to everyone for their suggestions and contributions.