I do services generally according to the maintenance lights, usually slightly earlier. Lights have been calling for service at 28,000 km (up from 25,000 km baseline due to our usage characteristics) but I do it at 20-24k, or 2 years, whichever comes first.

Same service practices for our last five BMW vehicles. This one has 110,000 on it. No oil consumption between services, since I sold the X5 (and it seemed to be related to being a heavier vehicle, since all five vehicles were inline 6 models).

I only use BMW 5w-30 now, but have used Castrol in the past. Only OE filters. Used Mobil 1 once or twice. Full synthetic, not the Syntec Blend. Don't buy the 'Castrol isn't a synthetic' argument. Mobil lost that court case, and it was a nuisance lawsuit anyway.

No sludge. None. Inspected.

We live downtown. Some short trips, but balanced out with highway trips occasionally.

I think that changing the oil every 3-5k is a waste of money, unless the vehicle only sees that mileage every 24 months, in which case getting the acids out of the sump can't hurt.

A waste of money to some is peace of mind to others. Which in the long run can be worth more than the money. :thumbup:

I still maintain 5k - 7500 miles is about perfect in terms of an interval. 10000 is too long for an oil change by my standards. Especially since, as others have mentioned, most of us who live in cities expose our X5's (and other vehicles) to what is considered a fairly harsh driving cycle.

Wow - that's a long interval...and you say 'no sludge'? I suppose this is okay if you only intend to keep the vehicle until it's turned over 100K kms or so then trade it in, but if you plan on keeping it for longer (200K or more), personally I would be inclined to increase the service intervals to half that at a maximum. As has already been mentioned several times, we generally use our vehicles in a harsh driving environment, so a more frequent transfusion of essential blood would/should be of benefit, especially so given the weight of our vehicles and how hard they get 'pushed' to move that mass.

i think it all depends on your driving style.. I live in nyc and I deal with tons of stop and go traffic so I do 5k oil changes. some people live in areas where it's miles between lights, and do about 50mph before they reach a red light so I understand why they see a 5k oil change as excessive

I used to do 8000 mile oc intervals earlier but now doing 10,000 miles or 18 months which ever comes first.

JCL, do you think your mild climate has anything to do with your ability to run oil longer and have no sludge? Any oil analysis to show it's ok?

I don't doubt you (been around here too long that I know better:thumbup:), just wondered if there was something other than visual data to go by.

If it feels good, then it is a good interval for you. I would just point out that there isn't any evidence that it is doing anything to extend the life of your vehicle.

These engines do not have problems with sludge, generally. If they are not warmed up completely, they can have problems with condensate, but not sludge.

It doesn't make sense to me that I can go 100,000 with no oil consumption, and then suddenly something changes after that and the engine wears out prematurely.

I have posted pictures previously of the internals of a BMW engine with 100,000 miles, on factory service intervals, and it looked pretty good.

I do service it more frequently than it calls for, by about 10-20%. That is a reasonable additional safety margin, IMO. Servicing it two or three times in the scheduled interval is a lot. Not many engineering calculations use additional safety factors of 2x to 3x over the design spec.

We have a mild climate here in Vancouver, but all of our BMW vehicles (except the Z4) were regularly driven up into the mountains and to Alberta, down to -30C on occasion.

If by sludge you mean condensate, then I think the secret is making sure the engine gets warmed up completely, on a regular schedule. We live in the city centre, and drive less than a mile to a grocery store. But that gets offset by regular trips where it gets fully up to temperature, and is held there long enough to make sure the moisture is boiled off.

I haven't done oil analysis, but the oil consumption figures (or lack of oil consumption) are a pretty good indication of no excessive cylinder bore wear. No mechanical failures of any type.

Many years ago I did oil changes at 3000 miles/5000 km, on my own vehicles, and promoted that schedule to customers. Vehicles, and lubricants, have changed significantly since then, IMO.

Jeff

If that is his generic recommendation (and it sounds like he would apply it to a wide range of vehicles) then how does he modify it based on sump capacity?

With heavy duty industrial engines, our customers often wanted extended oil change intervals. The way to do that most effectively was to double the sump capacity; that way the manufacturer supported a doubling of the oil change interval. More fluids could hold more contaminants in suspension, and the additives lasted longer. BMW vehicles have oil sumps that are generally twice the size of many other vehicles (8 litres vs 4, for example). That is part of the longer change interval design spec.

What I am not clear on is why the recommendation would be to extend the interval with synthetic fluids. There are too many other variables in play, and it sounds a little like a synthetic oil commercial. One of the variables is filter life; if you get a longer oil change interval without using an appropriate filter you may need to do an extra filter change at half the oil change interval.

When we were extending oil change intervals beyond the manufacturer's spec due to special service requirements (ie engines in remote areas) we would try to establish whether we could go 1.2 or 1.5 or 2 times the scheduled interval. We did a lot of extra oil sampling, typically 5 or ten extra samples on each engine. And don't start at the scheduled interval, you need a baseline sample of new oil, and then throughout the test period, as you want to see where TBN is dropping off, and not just get a figure at the scheduled interval. For most customers, it was more trouble than they wanted, but if you were flying crews in to do services then it could pay. Those engines were running continuously, in either power generation or pumping applications, with scheduled overhauls at 15k, 30k, or 60k hours depending on the engine series, load factors, and fuel source.