Best way to clean an engine, or parts really, I've found:

1. Buy Black Magic Engine Shine (2 or 3 cans if doing engine for first time)
2. Drive up onto ramps at home
3. Drop plastic spash pan (and metal reinf. plate if you desire)
4. Spray the hell out of everything, best on hot/warm engine, with the Black Black Magic (it's a foam and sticks fairly well)
5. Agitate extremely dirty areas with a painting brush, the more bristles the better
6. Let sit for 10 minutes
7. Hit everything with a hose on low pressure and finger in hose, or low pressure sprayer
8. Start engine to heat soak/dry everything up
9. Put reinf. plate back on and splash pan and you are good to go

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2005 X5 4.4i Build 04/05 Maintenance/Build Log
Nav, Pano, Sport (Purchased 06/14 w/ 109,000 miles) (Sold 8/15 w/121,000 miles)

2006 X5 4.8is Build 11/05 Maintenance/Build Log
Nav, DSP, Pano, Running Boards, OEM Tow Hitch, Cold Weather Pckg (Purchased 08/15 w/ 90,500 miles)

2010 X5 35d Build 02/10
Nav, HiFi, 6 DVD, Sports Pckg, Cold Weather Pckg, HUD, CAS, Running Boards, Leather Dash, PDC, Pano (Purchased 03/17 w/ 136,120 miles)