I have a 2014 with the AMG package and premium and some others. Car has 40k miles and has been very reliable. Debating if I should extend the warranty or not. We are definitely keeping the car for at least another 2 years. Here's what my dealer quoted me:

1yr or a total of 75k miles (would expire 2/14/19 or a total of 75k miles, whichever comes first) $2300
2yrs or a total of 75k miles (would expire 2/14/20 or a total of 75k miles, whichever comes first) $2530
3yrs or a total of 75k miles (would expire 2/14/21 or a total of 75k miles, whichever comes first) $2875

1yr or a total of 100k miles (would expire 2/14/19 or a total of 100k miles, whichever comes first) $2875
2yrs or a total of 100k miles (would expire 2/14/20 or a total of 100k miles, whichever comes first) $3162
3yrs or a total of 100k miles (would expire 2/14/21 or a total of 100k miles, whichever comes first) $4025

Our warranty ends in 2/2018.

 

You can ask yourself if any of these apply to you to determine if you would really benefit from a long warranty.

-Do I have an AMG hand built engine which requires constant maintanence? NO
-Do I have a V8 or V12 engine? NO
-Do I have a Bluetec Diesel engine? NO
-Do I have a complex Air suspension that when fails will cost at least $4000 to replace? NO
-How quickly would I reach 100 000 miles?
-Do I have massaging seats, nightvision, soft close doors, sun-roof, or other equip that is expensive to repair?
-Do I drive the car hard?
-Do I drive in a hostile environment such as salt roads?

I don't think you need to buy the additional warranty. The warranty wouldn't cover things that you need to replace soon anyways; such as brake pads, brake rotors, tires, fluids, and filters. The warranty protects you from a transmission exploding or an air conditioning failure, stuff like that.

 

Unfortunately, or fortunately for those with less mileage, the expensive stuff seems to start happening after 100k miles. Intake manifold $2500 @103000, Brake/stability control unit $1300 113000 miles. Cars seem to be too complex now days to go the long haul of 150000 to 200000 miles. Yes, there are examples of even 300000 miles but I don't seem to be able to get them or win the lottery. 75000 miles is not a lot, so I would suggest saving the cash and when the big thing happens, trade her in. The dealer can fix stuff cheaper than they charge and you will have an extra $3 to 4K to put down on the car. By the way, my dealer gave me an extra 3 years, after the original warranty, and unlimited mileage on a Certified Pre-owned for $2000 and a very good trade in even with a known problem on my 115000 mile 2010 GLK when buying a 3 year old GLK. At the rate I drive, it was the unlimited millage that made the deal.