Looking for any info. Has any one ever considered using an blue top optima battery in there tdi? I may need one and I was going to get a factory 48group battery when I ran across one at advance auto that had 800cca's and 120 min. reserve (or something to that effect). They have one in deep cycle and one in starting. How about the other colors red/yellow top optima batteries? Any opinions ? I know its not the same group but I think it will fit.