[AXMonster]

With regard to the oil bypass filtration system suggested by the OP I can say its a good cost saver in the long run for larger engines running on expensive synthetics. My LPg powered 3.2 litre Jaguar XJ6 used to have an TF Purefiner 1 micron filtration system that I fitted and it would run on Amsoil synthetic oil for approx 30k miles before a change was required.

The issue with running the oil for the life of the vehicle is that the contaminants in the oil are not just particles of metals and dirt etc, they are also acids that will corrode away bearings and even water, soot and other chemicals that can cause demege if allowed to build up.

The biggest indicator is the oil's Total Base Number (TBN). Its best to change the oil when the TBN reaches 50% of its original value (new, unused oil). This requires oil samples to be monitored at regular intervals and of course involves some cost.... but as it also reports on the condition of the engine (much like a blood test for us) its valuable in spotting problems before they become serious :-)

So, on my Jag the cost of oil was £50 per fill, and with an oil change being specified at 10k mile intervals it would have cost £150 for those 30k miles. Instead it cost me the £50 plus 2 oil sample tests @ £13 each, so £76 instead of £150. Half the cost!

The kit cost £215 tho so you can work out how many miles before payback :-o