I've noticed that the guys here tend to be "conservative" and tend to have low opinions of most of the products out there that claim to have benefits for our cars. What about MoS2 (Molybdenum Disulphide) as a friction reducer? That does not sound like snake oil to me. Old school proven technology. Lubro-Moly sells a MoS2 treatment that is added to the oil. I'm assuming you guys think Teflon oil treatments and the like are snake oil. I'm not sure (leaning towards "they don't work" these days). Slick 50 used to claim their Teflon would penetrate and stick to the metal in the engine. I'm quite doubtful of that today. I have used Slick 50 once or twice in the past with no ill effects (Mazda RX-7 and Toyota 4Runner). But in the Beemer... not so much. BTW, my 2000 528i has 147k on the clock.
I'm not a fan. I use the BMW synthetic in my E39 540. That or something equal or better and chenge it every 5 - 7.5k along with a filter, depending on your driving,
Nor am I, I have never believed in "mechanic in a can". I use Mobil 1 oils and change it every 3 - 7k depending on use. I do use Redline Si-1 Fuel Injector Cleaner occasionally.
A good modern oil negates the need for any additives unless the engine is in a vintage car and the new oil formulation no longer has the proper soft metals (ZDDP) for lubrication. In this instance, Torco's ZEP or equivalent should be added for upper valvetrain lubrication. For your car, sticking with a BMW recommended oil should serve you fine. I have a personal preference for a full PAO synthetic. I usually use Mobil 1, but will be trying German Castrol to see if a light valve ticking will go away as some have claimed. This stuff is not the same as Catrol Syntec made in the US though. For fuel injector cleaners, Chevron's Techron (used to and may still be used under license for Shell V Power) and Seafoam have been highly effective. Regular use of Shell V Power will clean out any engine as it has the highest concentration of detergents in any US gasoline. I don't make a dime off any of these endorsements nor do I work for any related companies as a disclaimer.
That's because we're smart enough to figure out that most of them don't have any benefits for our cars. If you feel you must spend money to feel better about your oil's friction, this one is as good as any. IOW, I don't think it will hurt. I'm a lot more certain it won't help, either. When it comes to E28s, that's called a "cream puff". I've never owned one with less than 165K and I've had three over 200K (two over 250K). Almost all saw autocross and/or track use. I use oil and I change it kinda' regularly.
Oil additives will not provide be any tangible reduction in friction over a quality synthetic oil. Several companies use a small quantity of moly as an anti-wear oil additive. Too much moly plugs small oil passages and oil filters. There is no need or advantage what so ever to using oil additives with current BMW approved synthetic oil. In fact oil additives can compromise the oil formulation so I'd definitely not use them.
I know he has an E39. The E28 528i was not imported here, although there are a handful of them here brought in as 'grey market' cars. I just changed the subject, that's all ...