I just did a half oil change by sucking out a couple of litres and replenishing with fresh oil. :-\

I'm reasonably sure my choice of oil will go the full distance (15,000Km here is Oz) when conditions are ideal but I reckon it's cheap insurance to do an intermediate change anyway, which up till now I've been doing a complete refresh at 7,500Km. This time though I decided to do something that some might find controversial and stretched the oil to 9,000Km and then, as I said, just replaced some of it.

The partially changed oil will do another 6,000Km before the lot gets dumped at the next scheduled service. So instead of using 5.3 litres a year for normal OCI or 10.6 litres a year when using intermediate changes, I use approximately 7.3 litres a year and waste less.

I'm sure it's a sound strategy partially based on reading reports that severe oil burners could almost get away with no oil changes at all because the oil is effectively getting changed by just replacing that which is lost.

Whatever strategy you use remember you must replace the filter at normal scheduled intervals.

Of course, to do as I have done requires that you suck the oil out because it will be impossible to do a half oil change via the drain plug.

[eye30]

Isn't doing this false economy as you didn't change the filter where if there are any particles which will harm the engine collect.

By doing a 50/50 aren't you asking for trouble as the lighter oil may dislodge the particles and cause engine problems.

For the extra £/$ I would have done a full change including filter.

[beerman]

Run it to 15k, and put some of the money saved to better oil.

The recomended service schedule is for the worst kind of driving anyway.

If your concerned do an oil test and see what they say.

I have never done anything more than the recomended services on any of my cars and have had no difficulty.

[simon@mgr]

Are you covering the 15k in more than 12 months, if so the oil has to be changed to remove the contaminates which accumulateduring this period. Even if you only did 10k you still would need to do an oil and filter change.
If the 15k is done in less than 12 months, you could try changing the filter only and just top up the oil lost.

[asathorny]

I too believe that changing oil without changing the filter is no better than not changing the oil at all.  Using a suction device to remove the old oil used to be quite common, s'pecially on certain boats, as the alterative would be to lift out the engine.

I also think that the advice from one of our techie members in which he states that most of us ordinary members probably change the oil far more than we need too, but have to comply with the warranty.

Being a person who never allows is lack of knowledge prevent him from have strong opinions on almost any subject you care to mention, I always speak my mind 

[beerman]

Are you covering the 15k in more than 12 months, if so the oil has to be changed to remove the contaminates which accumulateduring this period. Even if you only did 10k you still would need to do an oil and filter change.
If the 15k is done in less than 12 months, you could try changing the filter only and just top up the oil lost.

Well I do 15k in 6 months, so thats one reason, but even in the wife's car, I change the oil at the recommended time, no more. She still does the recommended number of k's in 12 months. The important thing is to make sure it gets a good run on the highway occasionally to burn off the stuff that has built up in the oil from short trips (again not a problem in my car, which wouldn't know a short trip).

[StarSeeker]

On my old car I used to do an oil and filter change once a year and halfway during that year, I would completely drain the sump and fill with fresh oil, leaving the filter.  I would only do about 10,000 miles a year and felt that changing the filter only once during that time was enough

[Dazzler]

On my old car I used to do an oil and filter change once a year and halfway during that year, I would completely drain the sump and fill with fresh oil, leaving the filter.  I would only do about 10,000 miles a year and felt that changing the filter only once during that time was enough

That seems a fair call to me..