[TimFromNorway]

Originally Posted by skyship007

The max OCI for older Volvo's is 20K km (12K miles) and 30K km for some new models. I've never known any OEM oil filter to block in under 30K km, even from an engine in bad condition and even if one did, they are fitted with a bypass valve, so it's not the end of the world.

How long the air filter lasts will vary a lot and I don't know what Volvo list for a max interval, BUT it should be inspected every oil change interval (OCI). When you remove an air filter to inspect it, NEVER use an air line to clean it, just tap it gently to get rid of bugs, vacuum out the housing and refit it, IF it looks good.

Unless you are using a UOA (Used Oil Analysis) program the OEM max OCI is too long for an older diesel and most owners use half that figure (10K km or
6K miles), but fail to understand that there is no need to change the oil filter.

Leaving a spin on oil filter on for a second interval is good news not bad in filtration efficiency terms and the extra 10% contamination from old oil does not matter, in fact it's good news for rather complex chemical reasons.

I change my oil every 10K km, BUT only change the oil filter every 20K km and get slightly better results from the second interval. That 2 for 1 game has been standard practice for marine diesels and Honda cars for many years. The only warning is that you should never try and drain a spin on filter, as it can cause a slight leak from an old seal if you fit it again. Also some non OEM standard oil filters use cheap seals, so I would only do a 2 for 1 using Volvo, Bosch or Mann filters (They should be stamped "Made in Germany) purchased from a reputable source.

The reason most OEM's don't recommend 2 for 1, is that owners often buy far Eastern filters that either fall apart or leak when old AND it complicates the service records.

Thank you once again for some really useful information!

Will order some Liqui Moly for my next oil change!