Because Ford won't honor the original battery with the same warranty as the replacement battery.
Last month the battery in The Old Lady's car died and I wrote a
blog post about it. When we checked on what was covered by warranties, including the extended warranty, the battery wasn't covered except under the original 3 year/ 36,000 mile warranty for the car.
A couple weeks later I was perusing the owner's manual to see when I needed to change the sparkplugs. It had over 50k, so I figured if it had standard plugs they were past due to be changed. That's when I saw something that got my hopes up.
This is a scan of a page from the owner's manual scheduled maintenance. It hypes how good their Motocraft batteries are and what great warranty they have. BULLSHIT!! When I saw that I called the local Ford dealer, in fact I called two of them when the first one wouldn't honor the warranty as stated in the owner's manual. Both dealers parts persons gave the same story. The battery is only covered for 3 years/ 36,000 miles when you buy the car. They did say the replacement battery was warranted as stated above. All that happened was they managed to piss me off by not honoring the same warranty on the original battery as they would on the replacement battery.
Then The Old Lady called the 800 number for Ford in the owner's manual. After talking to someone there and explaining what was in the owner's manual, that person checked and came back and said it should apply and that the dealer would get back to us in 4 business days. After a week, The Old Lady called again and got told the same thing. Then we kinda forgot about it and two weeks went by and The Old Lady called again and this time she got the same story I got when I first called the dealer. When asked what was the difference between the original battery and the replacement, the reply was they are the same. Couldn't get an answer why there would be a different warranty on the original battery if it was the same as the replacement.
The Old Lady wished her "Happy Holidays" and said she looked forward to buying a Toyota!!
UPDATE:
This is very true in this case, if they won't honor the warranty on the battery, what would make me think they'd honor the warranty if something major broke.