Dear Ian,

I had a similar drop in FE after my first oil change, but in hindsight I think the FE drop was caused by something else - outside temperature.

I took delivery of my TCH in early September. I decided to have the dealership change out the oil at around 1500 mi (I'm used to the "old school" approach to break-in). I specified 0W-20, as the manual suggests. After some wrangling with the dealer (described in a post in another thread), they put in the 0W-20 (at least I think they did). At that point, I had driven about three tanks in the car, my average FE was around 41 mpg and my highest tank average was 42.3 mpg.

Anticipating similar or higher FE on the next tank, I was disappointed and a little upset to see my tank average begin to erode (I am now at 40.3 mpg with 75 miles to go on the tank). I drive mostly locally, as part of my law practice. Most of my trips follow the same dozen or so routes, so I kind of know where I should be on trip FE at any given point of these routes. I found I was coming in lower consistently at these "checkpoints".

As I now analyze the situation, I can only conclude that the average ambient temperature must be the key factor. My first three tanks were used in weather I would estimate to have been in the high 60s-low 70s. My current tank has been used in weather with highs in the low 50s.

Bill
2007 Magnetic Gray TCH/Nav/Ash Leather
2002 Blue BMW K1200RS
2000 Champagne BMW K1200LT