I've had great success with my Yellow top Optima - in my 240z - it's
definately the best battery I've ever owned. - I've even forgotten to
disconnect it through the long Ohio winter storage season - but it still
cranks like new in the spring.....

FYI - the company I work for makes most of the batteries discussed
Optima, Die Hard, Duralast, Interstate - ......Johnson Controls.......