Here is the deal on MBI:
As far as I know, only Geico offers it.
For obvious reasons it has to purchased when the vehicle is very new... IIRC 6-10 months is the cutoff.
It will pay for mechanical problems that the factory warranty for some reason will not. There is a small $50.00 ? deductible.
As I suspected when I signed up back in 2010, the rate goes up over time.
At first I was paying $16.00 for 6 months. It slowly crept up a dollar or two every 6 months. My 3/36 warranty expired in August. My December renewal reflects Geico's increased risk of a claim, as the premium jumped to 32.00 for 6 months.
Still a very good deal. I am sure that when the 100K powertrain warranty is up, that it will jump substantially.
What is interesting is that the GMs consistently have lower rates than the Fords for this coverage. My 3 1/2 year old GM is less than a brand new Ford!
Insurance companies are VERY good at putting a dollar figure on their exposure to risk. It is what they do for a living.
We amateurs should pay attention to what the professionals do in this area.