Originally Posted by m6pwr
3000 mile oil changes went out with ducktail haircuts and penny loafers. Where have you been for the last half century?
Read the owner's manual and follow the oil change interval prescribed by the CBS (condition based service) computer shown in the dash. Earlier oil changes are wasteful and unecessary.
I've been told by a very experienced euro-based lubricants engineer (Doug Hillary) that BMW does very extensive field testing on each of its models to establish effective and safe maintenance and lubrication schedules. Doug currently works for Mobil, but has worked also for Castrol and in collaboration with BMW specifically on the development of the TWS oil for M cars. According to Doug, BMW uses two independent field testing outfits and he knows personally some of the engineers there. These guys know what the hell they're doing - - more so than anyone on this or any of the other BMW forums (and that includes me, for sure) when it comes to lubrication.
Shortening the factory specified oil change intervals achieves nothing with regard to the longevity/durability of the engine, other than conveying that elusive "peace of mind", and this includes the practice of dumping the factory fill at 1500 mi to wash out all those nasty wear metals (even if BMW says itís not necessary on your car - - after all what does BMW know Ė they only make the engines). The practice of gearheads dumping the factory fill at 1500 mi on a new car is a holdover from the days of push rods, carburetors, and bias ply tires.
There is even some recent data/testing (done by Ford and Conoco Philips) that indicates too frequent oil changes may actually be counterproductive. They did tests (published in an SAE paper) that showed that what they called aged oil, or oil thats been in use for awhile, sets up and actually does a better job of lubricating, particularly in antiwear, (up to its condemnation point) than green, fresh oil. So more frequent oil changes may actually increase wear. Heresy! There was a similar study done (I wished now I had bookmarked it) specifically with regard to the antiwear add zddp, that showed fresh oil would dissolve and remove the tribological antiwear layer laid down by the old oil before it would form its own layer. Hard to believe. With respect to the direct injected turbo motors (like the N54/N55) Hillary has even said that he has seen what he calls very reliable data that indicates shortening the oil change interval "negatively affects" the formation of deposits - - the fresh oil just feeds more deposits before it stabilizes.
There was a recent rant (maybe on this forum - - canít remember) about the lack of a dipstick on some of the latest BMW engines. Actually, you should be happy. That is an indication that the motor is equipped with a neat device designed by Bosch called an oil condition monitor. It constantly measures oil level and the dielectric properties of the oil. As the oil (very, very slowly) ages, picks up wear metals, acids, fuel dilution, and oxidizes, the conductivity or dielectric properties of the oil changes. Thatís where all that field testing comes in. BMW can correlate the electrical values measured at any one time to the general condition of the oil and adjust the oil change interval if the oil is in danger of becoming unserviceable. Boschís latest oil condition monitor even has a little transducer that bounces sound waves off the oil to measure changes in viscosity. What more do you want?
In spite of all this, we doubt BMW. We love the engineering that goes into the car but somewhere in our reptilian brain some atavism, some primordial fear, tells us the engineers canít be trusted, that if we want the car to last we must halve the oil change interval to 7500 mi or 5000 mi or whatever.
Iíd like to challenge anyone to post a link to a contemporary, scientific study by a reputable source that shows shortening the mfrs recommended oil change interval will increase the longevity and durability of the engine. And I donít mean Mike Millerís Old School Maintenance Schedule. I mean a study reported by the Society of Automotive Engineers, or the American Society of Mechanical Engineers, or the Society of Tribologists and Lubricants Engineers - - or similar.
And if you want to impress future buyers when you sell the car, show them UOA (used oil analysis) reports from a reputable ISO certified lab like Polaris (not Blackstone - - they don't do a good job on fuel dilution) showing that the oil you changed according to BMW's schedule was rockin good, and with the BMW it so well engineered that you don't have to spend $$$ doing oil changes at 5k, 7k or whatever.