It probably wasn't surprising. Given the BMW X6's performance and distinct lack of practicality, it was ripe as a target from environmental groups, even in Hybrid form. Recently, automotive engineers at the Union of Concerned Scientists have declared, in an update to their Hybrid Scorecard, that in a comparison against the the Mercedes-Benz S400 Hybrid, the BMW ActiveHybrid X6 "squanders its hybrid drivetrain in favor of boosting power, while the Mercedes-Benz S400 hybrid achieves some success in lowering costs by combining its relatively weak hybrid drivetrain with a downsized conventional gasoline engine."
The X6 is BMW's first hybrid on the market, using electric power to supplement the twin-turbo charged 4.4-liter V8 engine, delivering stellar performance, but according to the UCS a relatively poor score of 4.4 out of 10, not helped by a $10,000 sticker premium over the standard X6. By contrast, the Mercedes S400 Hybrid, which uses a six cylinder engine, but is still a mild hybrid (meaning it cannot run on electric power alone) is priced below the conventional S550, garnering greater UCS approval. The Union also dubbed the BMW's price premium as "forced content" stating that such a marketing strategy unnecessarily drives up the cost of hybrid cars across vehicles classes. And we thought it was technology.
More: "Concerned" Scientists Give BMW X6 Hybrid a Failing Grade on AutoGuide.com