Purchased the second tier from the dealer at the same time that we purchased car. We had to replace the water pump after two month (Which Diamond told me later that they made a mistake by accepting that claim).
Head gasket went out on car a couple weeks after that and Diamond would not cover the replacement even though it was part of the warranty that we purchased. They stated that we drove the car hot too long so it was our fault. We had the car of six month and it's been in the shop about 3 of those months in total between the two claims waiting on a decision from Diamond. They gave us a big run around and then finally denied the head gasket claim.
Don't waste your money. Could have saved myself the 425 dollars for the six month plan!
Review about: Diamond Warranty Warranty.
Monetary Loss: $1900.