As mentioned, read the E70 forum and the Diesel forum. I strongly considered an E70 diesel when I decided to get an X5. It seemed like the perfect answer for my occasional towing needs and my disdain for poor fuel mileage. After researching/considering, I ended up buying a gas powered E53 instead. The cost of maintaining the emission systems and the fact that I fairly frequently make short trips, led me to the decision that a diesel just wasn't a great fit for me. YMMV.

AM.

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E70 2010 3.0 M57 AT Titanium Silver with Black Leather
E53 2004 3.0 M54 AT Toledo Blue with Gray Leather
E83 2008 3.0 N52 AT Silver Gray Metallic with Black Vinyl
E46 1999 2.8 M52TU 5MT Black with Tan Leather 250K+ miles (Sold, but not forgotten)