Originally Posted by JCL

I've been changing oil in my own and customer vehicles for over 35 years, so I spent a lot of years living the 3000 mile/twice annual oil and filter change interval. It was the bible for longer engine life in those days. I don't think it is at all relevant today, unless it is an engine from that era, using older oils.

When I first went to longer oil change intervals on a new early 90's BMW 3 series, I checked and saw how it did on annual changes. It did fine.

With my new 2003 X5, I began to move towards the recommended intervals, but capped it around 18,000 km and 18 months. That was on the oils that were current in 2003, not API SM or SN oils. My last three vehicles have been run closer to BMW recommended intervals, on BMW oil. The X3 last called for 28,000 km but I did it closer to 20,000 due to some shorter trips. That is still 30% more frequent than the CBS system suggested. I left the oil in 2 years, and was comfortable with that. Oil condition was fine. The 535 was fine at 24,000 km, still no CBS call for service. No oil consumption on any of these vehicles to speak of, and the last two hardly took any makeup oil between changes, in the order of 1 litre every 10 or 12 k.

So yes, I do think time matters as well, but I would have no concerns with going 2 years. I wouldn't go much beyond that. A few months wouldn't matter to me, but I think 3 years is too long, as an example. Also, there are other things that are a fixed 2 year interval (ie brake fluid) and since I no longer have a garage to work in, I am using a shop, and I get them to do it all at once.