Been using and dealing with Optima for many years. Actually I brought this battery to the retail market back in the day. Our Company has sold more than anyone.
Here is my experience from our customers an some with the GT an other personal cars.
1. They have an above average life on daily driven cars. Seen 9 years an still going in my son's WS6.
2. When drained completely they are much more difficult to revive. May not be able to jump start, either.
A. For some reason when very low, they do not do as well with a jump pack device either.
3. If they have some charge left they will come back when using a trickle charger.
4. High amp chargers and an Optima are bad news. There is not enough mositure in them for this and it drys the spiral cells very quickly. Steve A mentioned this with his dealership experience. Very common occurance.
5. Charge at 10 amp max when in a jamb. 2 Amp is what they like best.
6. GT electronics act up when you don't have a fully charged battery. The gauges will do funny things. Because it starts, it does not mean the GT has a fully charge battery. Once it becomes fully charged the electronics seam to get back to normal in almost all cases.
A.
Don't assume it's your battery if there is zero power, either. There is a
ground that goes to the X frame near the battery. This 10mm bolt has been the culprit in the past. A 1/4 turn of this bolt can bring things back to life. If you have voltage an no int lights, brake lights or headlights. Look here first.
7. The factory charger cig lighter charger will not revive a very low battery in my experience. A minor dis -charge it works fine. No lights or state of charge reading is No Bueno for me.
8.:thumbsup Kendall aka Cooltech sells a charger system for the GT that makes it easy to keep the battery tended to automatically. Highly recommended for the enjoyment of the car at anytime.
This should be at the top of any mod list IMO. I was a little lazy and let mine drain too far one time, my first call was to Kendall. Some of us don't get to drive the cars enough with travel schedules, winter storage, etc. He has done a good job customizing this well known and reliable device for the GT. Brought this charger to the retail market as well. Very reliable unit.
Check it out here he has some very detailed information.
http://www.cooltechllc.com/ford/gt_chargeport_gt_float_charger_kit.htm