As we all know, honest john repeatedly advises that no engine oil can stay in grade beyod 7500 miles. Hence, many of us routinely change oils frequently and achieve high milages.
However, car manufacturers say that the oil manufacturers now produce oils that meet their requirements for extended intervals such as 18,000 and 30,000 miles etc. The oil manufacturers own websites cofirm that they produce oils that are 'specifically designed' to meet the requirements of car engine manufacturers.
BMW says to me that their experts know far more about oil and engine set-ups than honest john. So does anyone reading this have any evidence or data that scientifically evaluates the performance of a fully synthetic oil in terms of its ability to remain in grade over for example 18,000 miles? Lets assume fairly average driving over 18 months for the sake of argument.
I am hoping that oils have demonstrably improved to the point where motor manufacturers are not deliberately ignoring the damage that could be caused to our cars by too infrequent oil changes!
Cheers.
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Mineral based oils will break down and lose their properties over time. This is due to the effects of heat, pressure and contanination (water, acids, particles etc)
Synthetic oils do not break down in the same way as mineral oils and hence can last a lot longer. But they still have the problem of becoming contaminated. In the US there is a DIY kit available which will enable you to get up to 50K miles (alleged) between an oil change. It involves installing an additional oil filter that will remove the very small carbon particles that build up. The filter needs to be changed every 10K miles (I think) and the cost of the filters probably negates some of the benefits of extended oil changes.
I think that synth oil will remain in grade over 18k miles but the problem is the build up of fine particles that the filter can't trap. If the BMW filters can trap the small particles then with regular filter changes the 30K interval may be ok. If an extra fine filter was used then not changing it on a regular basis could be risky as I guess it could easily become clogged and reduce the oil pressure.
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S'funny but I raised the extended life via additional/enhanced filters on the discussion forum today.
These filters are already used by some heavy commercial vehicles, the issue of it becoming clogged shouldn't arise as there should be a bypass valve.
This could also flag a filter change alert when the bypass is activated.
Still doesn't sort out muppets not checking their oil level!
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Some places that have large fleets use oil analysis to verify change intervals. Some motorcycle enthusiasts in the US send oil samples off to check contamination and viscosity.
Me, for the price of oil and a filter, I'll change it on the car spring and autumn and on the bikes when I change the rear tyres (less wear = gentle use, faster wear = heavier use). It's cheaper than sending a sample away (oooer) and only takes 30 mins.
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I can't answer the question about staying in grade, but there's also the issue of the crus that goes round with the oil, as has been pointed out. I have always assumed that the darkening of the oil is mainly down to very small particles that the filter doesn't trap - mostly harmless carbon maybe but possibly other stuff.
Like many, I change oil between scheduled services - i.e. every 4500 on my CRV and 6000 on the boss's Civic, even though I use Chevron synthetic (about £12 for 4l. from a well known warehouse club.)
I confess I do this because "it can't do any harm", but also because the manufacturers do have an interest in "stretching" intervals on cars that mainly sell to fleets - some are now up to 20,000 or more and this makes them look cost-effective to run to fleet managers. Any penalty in longevity is usually visited on the second owner! I don't know if they still do it but Ford used to legitimise "high mileage" servicing with longer intervals which although rationalised by theoretical lower wear rates was clearly a benefit to fleet managers.
Even models that sell mainly to private owners have to follow suit to some degree - we are all getting conditioned to think that 6000 services are a nuisance and unnecessary.
Aren't the long life filters in large commercials usually centrifuge types? These should remove the smallest particles if they are denser than oil, so its rather than they make the oil long life rather than being long life themselves?
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For the sake of a few quid why not have an intermediate oil and filter change? When you change the oil at 1 year or 12,000 miles it looks black and treacly - how long has it been like that, and would you consider pouring it back into the engine?
You could spend more money discussing this on the internet than it would cost to change the oil/filter!
Sorry, but it seems a no brainer to me.
Pat
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In the light of some good responses to my ealier prose on oil life and intervals, and the discussion going on in the other place (discussion forum) with a piece from HJ asking if BMW would guarantee its engines for 200K on its service regime, I thought I'd try a few oil manufacturers. To date, only Millers will talk openly. There view is that the oils are manufactured to run to long service intervals with the corresponding massive advances in engine technology. Yes, they say the best oils will stay in grade! Clearly common sense prevails according to the type of driving, but engines so designed will have fine micon particulate filters which will do the job!
I have yet to have a useful response from BMW giving their views on such long service intervals or guaranteeing their engines for 200K. I suspect I already know what they will say, eventually.
In the meantime, I will be changing my oil long before the 18,000 miler comes round.
Excellent Millers web site with free 0800 technical enquiry support. II already feel I want to trade with Millers!
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I don't believe engine life is fundamentally down to either engine technology or oil technology. I think it is quality of manufacture coupled with frequent oil changes.
All Volvo models back to the P1800 and probably earlier have been good for an easy 200K if serviced properly. This probably applies to lots of other quality cars.
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<< I don't believe engine life is fundamentally down to either engine technology or oil technology. <<
Sorry, Cliff, I disagree. Engine life is very much down to engine and oil technology, witness the typical 25,000 mile engine life of some post-war Fords which was almost certainly due to things like having no air filter, using cheapo materials for crankshafts, etc. and running on the straight mineral oils of the day.
I agree, of course, that engine life can be extended with due care. We both run Triumph sixes which are known to have a fair engine life when serviced to the book, this being down to the technology. I serviced mine every 3000 miles instead of the scheduled 5000 miles and it was still running OK at 180,000 miles, albeit with some piston slap due to the long stroke (i.e. due to the technology). It would have gone on a lot longer with new pistons but I had a spare engine to hand so I overhauled and fitted that.
I don't know how many miles my second Triumph engine had covered but it was in very good condition even though it came from a scrap car that had ten previous owners listed in the log book! It had standard crankshaft journal and bore diameters so I don't think it had been overhauled - and I bet that not all ten previous owners serviced it between schedules!
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I think you are right Dizzy, it's my sloppy use of the word technology. What I meant was, the sound manufacturing and engineering principles of making an engine that can do 200K have been known for at least 50 years. Royce knew them in 1908 even!
And plenty of cars going back in time have demonstrated that they work - as I said, look at the Volvo Amazons to name just one.
I meant that I was unconvinced that there was any significant NEW technology that gave modern engines a magic new lease of life, except perhaps that it is now more cost effective to apply them to mass-production cars, not just quality ones.
In the past people looked after cars incredibly badly - look at all that old advice about leaving them to warm up before pulling off, blipping the throttle when turning off to put some petrol in the cylinders for next time, using the choke as a sort of boost to help getting up steep hills, etc.
Starting with one of the good designs (not the ones without oil filters!), driving properly, and changing an ordinary oil and filter frequently, I'd bet a good many older cars would have lasted the 200K too.
My next classic's an Amazon, so I'll try it!
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Cliff,
I go along with much of what you have said but I still say that there have been lots of improvements in technology that extend engine life. Whether or not you would classify these as "significant" is difficult for me to say.
I have in mind such things as tufftriding and nitriding to massively improve crankshaft strength and life. Or the deep fillet radiusing that Perkins applied to the Prima crankshaft to improve the fatigue strength by at least 50%, this massive benefit appearing to be unknown before the mid-80s.
We also now have precision cylinder bore honing that gives a special diamond pattern to hold minute but specific amounts of oil during engine running-in, to the benefit of bore life. Couldn't be done without modern high-tech honing machinery.
We also now have oil seals made of nitrile rubber at the least, with higher performance ones made of silicon or fluorocarbon. Not so long ago, seals were either leather (seepy), natural rubber (short lived with oil) or labyrinth (air gap seal, prone to wear and dirt ingress).
Castings are now much stronger because, for instance, phosphorous and sulphur inclusions can now be much better controlled. Also computerised systems like process controls are fairly modern technologies that benefit engine life by making sure they are built to a set standard.
Those are just a few things that come immediately to mind on the engine side. There are lots more relating to improvements in oil, like the replacement of straight mineral oils with multigrade oils and, more recently, the widespread use of long-life synthetic oils. All since 1908 I'm sure!
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BMW may have reduced their standards of engine life with their recommended service intervals, but I very much doubt it.
My brother's K-plate (newer shape, sorry I don't know the E number) 325i is on about 175k miles and going very strongly on only the services indicated by the in-car lights. Serviced by a main dealer to 100k and specialist thereafter. Having driven the car recently I would be VERY surprised if the engine would not run to 300k, but I think the bodywork will be a mess by then.
Personally I do oil changes more often though!
Andy
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This is an interesting addition to the thread - rather than our suspicions about manufacturers being a little optimistic about oil change intervals, how many of you have high milers that have been serviced in accordance with manufacturers specs only and aren't spitting the dipstick out yet?
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