Oil Change Question

[Transporter]

Yes, you‘re correct there, when more pressure is needed for the oil to get through the filtrating element, the bypass valve in the filter will open. When the filter is clean there is a less restriction to flow, the bypass valve may stay closed, but as the filter is getting more clogged up the bypass valve will start to open to allow unfiltered oil to lubricate the moving parts, since the dirty oil is better than no oil.

I don’t know what is the micron rating of the OEM filter on Skoda and VW engines, but I could speculate here a bit; since it is a long life filter (as brad say 30,000km/2years) which is not really big in size and has a back pressure set to 2.5 bar, the micron rating could be around 50 or 60 microns. Which is not good for short trips and oil changes every 15,000km or 1 year or even longer.

Anyhow regardless of the age of the filter and the oil, the bypass valve in the filter also opens at high engine RPM’s to keep up with the lubricating demand of the fast moving rotating parts. With the dirty oil and filter, it opens sooner and for longer.

A bit of reading for those interested Oil Filter Advice good info if you do extended oil changes.

[R36FTW]

Yeah would like to know its micron rating. Most paper element filters are something like 98% at 30 microns and 85% @ 20 microns, and most engine wear is caused by particles 10-30microns, which when you think about the particle size in relation to the bearing/piston to cylinder clearances is quite large.

There is no way I'd run a filter for 15000kms if I could help it. The filter doesn't get more efficient as it approaches 15000kms, the gunk may catch more small particles but the bypass will be open for longer and more often so unfiltered oil will be circulating throughout the engine more often. This is hugely detrimental and will rapidly accelerate engine wear.

[Transporter]

Here it is. Scroll to page 10 in the document for the filters data. http://www.mann-hummel.com/industria...BMAJHSgWGg.pdf

It wasn't that hard to find it.

[R36FTW]

W930/21 - 99% 38um / 50% 14um - Seems about right for paper/cellulose media, nothing special.