Auto Parts: size of battery, jetta tdi, heat absorption

Question
I am need of a battery for a 2002 Jetta TDI. Most places want to sell me a 765cca, but they offer a 700cca at a much better price. What size came in my car. Husband thinks maybe a 650cca. Thank you for your help.

Answer
    That's going to depend on where you live.  If you live in Florida, South Texas, Tucson,. or San Diego you can probably get away with a lower rating.  But it is always best to get the most powerful battery available for any diesel-powered car.  They are harder to crank in the cold because they have thicker oil and higher compression.  And, they crank longer due the heat absorption by the cylinder walls.  If it has glow plugs, which it undoubtedly does, they constitute an additional drag on the battery.  Add that to the decreased current delivery in cold weather (it can reduce the power of the battery to half of its normal rating) and you have a real job for a battery.  Don't buy a "universal replacement" battery for a car like this.  The correct battery for your car is a group 94 (there is a group number assigned to every battery configuration; Ford trucks, for instance, use a group 65).  A group 91 (which was used in older diesel-powered VWs) can be made to fit, but not exactly.  Find a group 94, pay whatever it costs, and be happy that it won't give you any problems.