Hello, Sorry if this should be in technical section, but I decided it was more of a subject for discussion.
We have two cars - one Audi A4 (petrol), and a just aquired VW sharan (TDi). Both are on the variable servicing plan - the Audi is now 15 months old, but has only covered 8K and is indicating that a service will be due in the next 6K or about 3 months time, so given the low mileage I have no problem with that, but the Sharan is the main family workhorse and will cover anything up to 20K per year. I have searched here before and the main opinion was that you should either return to fixed servicing, or oil change in between.
Given that the long life servicing has been out there some time now does anyone have any real experience of it in terms of how long they get between services, and any reliability issues with big service intervals outside of warranty?
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My A4 2.5 TDI asked for its first service at 13,000 (9 minthas old) and the second at 27,000 (about 18 months old). Sounds about right for a diesel: I should think your Sharan would be about the same.
Touch wood, no reliability issues at all.
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My 105bhp TDi GolfV asked for its first service at 18500 miles. I suspect it hit its maximum programmed mileage limit, as this is 30000 km and my usage (daily 135 mile round trip motorway commute with little thrashing) must be conducive to long intervals.
If the system is measuring the quality of the oil, then I guess changing the oil 'in between', eg at 10k, with longlife oil, whilst leaving the car set to variable intervals, will mean that the max distance between changes limit is more likely to come into play.
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So exactly what component in the engine check oil quality and how?
I suspect its probably just a crude miles v temperature comparison.
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TourVanMan TM < Ex RF >
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As mentioned in a recent thread, VW state that sensors are used to monitor the oil quality.
See www.volkswagen.co.uk/assets/Longlife_servicing.pdf
Where's Sean?
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Yes I know they say that but what or how? Does something shine a light throught it? measure viscosity? its dialectric properties? somehow I doubt it it sounds like carp to me.
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TourVanMan TM < Ex RF >
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Hmm - this extract from Audi's magazine (in 2002?) talks about sensors that
"...assess the parameters that influence the ageing of the oil. This information is fed to the CPU (central processor unit) that then tells the driver the distance or days to the next service. Influencing factors include the number of cold starts ? the toughest time for any engine ? and the loads the engine has been put under as reflected by the car?s fuel consumption."
ref:
www.audi.co.uk/experience/magazine/article.jsp?id=...3
No doubt this would add to your scepticism, TVM, as it's not quite the same as sensors that measure the oil quality...
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Merc's have an infrared oil quality sensor. They're also (allegedly) able to tell how many cold starts, full power accellerations, use of kickdown etc take place. Although there is a school of though that says the car just measures the fuel consumption.
One thing it will do, is if you add oil only when instructed to add 1L, then it knows you've done this (either by the oil level or the oil quality sensor) and it extends the service interval.
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Bill
I've read that BMW used to monitor cold starts, time run below certain water temperatures, time above 4000 rev/min etc to obtain an indication of oil aging and thus affect the miles allowed by the servicing computer. However, I believe they came to the conclusion that total fuel consumption gives an analogue of such parameters, and is much easier to measure. Apparently, this is what's now used.
JS
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Am I allowed to refer people to www.uk-mkivs.net where this has been discussed extensively under their Golf MKV and Jetta sub-forum?
My new Golf has covered just 7k miles in almost exactly 12 months (below average mileage) and is on variable service and so am expecting a service sometime in the middle of next year when "The computer says 'yes'".
People allege all sorts of fancy measurements that are made by a sensor monitoring the sump oil, such as clarity, acidity etc. but as you say I would rather think that it is a simpler computer-related assessment based on distance/Number of cold starts/temperature attained or perhaps something along the lines that BMW cars use?
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Oldgit - bear in mind that on variable servicing, the service call MAY only appear at up to 30,000 miles, but that somewhere in your service Schedule, it will say that you should have a service carried out at 2 years.
Also bear in mind that VAG do not recommend the variable service routine where the car is doing less than 9000 miles per year (check out the pdf link in one of the posts above and look at page 3)
hth
Go on, get out of the car...
www.mikes-walks.co.uk
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In the lab the IR transmission of oil is used to detect impurities (i.e. suspended soot etc.) - however I doubt this would be much use of a vehicle. For a start, some form of calibration would be needed. There are so many oils out there, most of which have not only a complex range of additives, but also dyes added - the appropriate chemical, electrical or optical changes would be almost impossible to nail down. I do not believe there is any sensor involved in the VAG system - as others have said, it is much cruder than that....
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