another car question...

[meriad]

My car is displaying error code 82. I called the garage and apparently it means that the quality of the engine oil is at it's end and needs to be changed... nothing to do with quantity of oil apparently; its only the quality of the oil.

They recommend that once the level goes below 3% the car should go in for its service. Now it's already booked in for just over 4 weeks time; is there really such a thing as engine oil losing it's quality that badly that it can ruin an engine or should it be safe enough for me to continue driving until date of service (currently sitting at 4%?). I could bring that forward but would rather not. Any ideas?

thanks as always to all you clever people out there x

[Workingman]

Ria there are many ways for oils to lose quality, but in a car engine the two main ones are 1. loss of viscosity and 2. the oil gets dirty - particulate matter.

1. happens due to the oil being worked. It is constantly being stretched and compressed and becomes *tired*, just like us. With modern synthetic oils it should not be much of a problem if it is changed when regular servicing is carried out.

2. is inevitable due to normal wear and tear and the piston rings working properly - it is why they have oil filters. Again, it should not be a problem under normal servicing.

That, then, brings us on to servicing. There are roughly three servicing schedules - time based, usage based, or a combination. For example in older times machinery was serviced on a calendar basis, which is why we had an annual service of our cars. Your car could be on a combo schedule, so you might have some leeway. The countdown to your cars next service has 4% left - be that usage based or on a timer.

The figures show that you have roughly two weeks left. 4% of 52 weeks is two weeks whereas 4% of a 10,000 mile service interval is 400 miles or 192 miles per week.

If it was my car, which is out of guarantee, I would stretch things out till the service already booked in because I do not feel that the oil is going to *fail* in that time. However, if the car was under guarantee I would bring the servicing forward by a fortnight just to keep that in place.

[Suff]

Ria,

But for the changes I've seen in oil technology over the last decade and a conversation with my son in law two weeks ago, I would have replied as WM did.

For 7 years understanding this was my daily working life, however time goes on and things change.

Most of us understand a bit about oil and how it works with cars, many of us have experience that oil will last well beyond the stated lifetime given by the manufacturer.

Sadly, with technology changes that has changed and in order to make the correct decision I need to talk a little (just a little), about that.

Oil has a SAE rating. Essentially what that rating tells you is how thick the oil is at each temperature. SAE 10:40 means that an oil is of a viscosity 10 at cold temperatures and 40 at high working temperatures in an engine. This is vital because if you used a 40:40 oil in a car you were operating in, say, Alaska, the oil would be too thick to pump around the engine at startup in very cold temps and it would destroy the engine. Equally if you used a 10:10 oil in the Sahara, the oil would not offer any protection at any temperature and the oil would be too thin to protect the engine.

A 10:40 oil is a compromise where the oil itself has additives which thicken the oil as it heats up so that it will provide the protection needed at each operating temperature.

As computer engineering has advanced, the tolerances within the engine have become smaller, requiring thinner oil for it to work and be protected. Most very modern cars have 0:30 oil. 30 years ago nobody would have put an oil with a top SAE of 30 in a vehicle, it wouldn't have lasted 30,000 miles without destroying it.

The conversation I had with my son in law, two weeks ago, was around what happened when his son put the latest 10:20 fully synthetic oil in an old VW beetle.... Totally destroyed the bearings in the engine.

So, after this long explanation for a simple statement (I wanted anyone who knows a bit about oils and tolerances to understand this), in short, if your car is monitoring the quality of the oil, it is because the oil itself doesn't have much tolerance and that you must be using oil which has not degraded over time.

If a car is monitoring the quality of the oil and it says change it, that is because the engine will sustain damage if you go below the tolerance level; because the manufacturing of the engine requires an oil which is so thin that it can only protect the engine if it is virtually pristine. Naturally if it gets thinner (quality drops), then it is too thin and surfaces will start to wear and that is a very short slope to disaster.

I would reschedule the service and get the oil changed.

[meriad]

thanks so much - knew you'd be able to help

Well, interesting - just spoke to the garage to bring the service forward and they said that it's absolutely fine to wait until the date I have it booked in anyway. so I've left it for now and will call again tomorrow and if I get through to someone else, see what they say

To be honest, keeping the date will make my life easier for various reasons, so I'm not too unhappy

[Suff]

Dealers....

When Peugeot/Citroen changed their service interval to 10,000 miles, some of the models were running dangerously low on Oil. Dealers just did what the manufacturer said and ignored it. Then refused to provide warranty repair on low oil because that is an owner/driver responsibility.

I doubt it will make much of a difference. Just be aware what dealers are like..