For coolant, I’ve been sticking with Zerex G-05. It’s suited me very well on both my European and Asian vehicles. I typically dilute full-strength coolant into a 33% mix with distilled water. I’ll also add a surfactant to my mixture to improve heat transfer; I prefer to use RedLine’s Water Wetter.

Motor oil is a giant topic. I’m a big fan of Bob’s the Oil Guy forums (BITOG).  The volume of information on this site is astounding…overwhelming…confusing. I spend a good bit of time looking into what fluids might work best for the BMWs that pass through my life. The older motors tend to prefer heavier base oils. My preferred lube for the M30 is Mobil1 15w50 (full synthetic). I know it’s not a ‘real’ Group IV synthetic, but it’s a very competent motor oil. My proof was provided by a testing lab that specializes in this sort of thing: Blackstone Labs. I recommend them highly and without reservation. Contact them for free sample containers. For only $25, you’ll get a superb report on your motor’s actual condition. Another $10 and they’ll let you know how well your oil is lasting. Tracking these reports for a few years will give you an excellent idea of how effectively your lubricants are performing. I’ve done a good bit of testing on both my M42B18 and my Mazda MPV’s (Ford) Duratec 3.0L. The Ford motor performed well with thin 5w20 as spec’ed, but that same motor oil was a poor choice for my BMWs. While I was getting spectacular fuel mileage with thin 5w20 synthetic, engine wear was very high. When I switched back to thicker 15w50, wear dropped dramatically. I now run 10w40 year-round as a good compromise. As for that big lump of an M30, I’ve been using a thick 15w50 conventional to break it back in gently. I’ll be thinning that out with a strong dose of Marvel Mystery Oil and some aerosol SeaFoam. With any luck those two will work together to break up a decade of carbon jamming up the compression rings.