I was thinking about options for improving the performance and/or economy of my diesel. I see that something called the Synergy gets mentioned a few times, and seems worth looking into.
But what about the insurance? I'm worried that an obvious black box like that will result in an instant invalidation of the insurance should I be involved in an accident. Obviously the thing to do is declare it. But have any of you done that? And how much extra did the insurance company want?