So I just bought a used 09 Lancer GTS, 5sp manual and the battery seems weak on starting, especially if I stall the car. The current battery in there is rated at 550. I've read through some other threads talking about vented batteries...etc. I went to Batteries plus and they have a Duracell Gold for 640 at $124, its a flooded battery, and the other option is a their brand AGM battery rated at 740 for $289.

I'm guessing I should have gone with the AGM? Would that be the better option?

I've seen mixed reviews on the optima red top and battery location.

 

Red top fits fine & works well.


I had to add some washers/spacers to the tie down bolts.

 

I know it's a little late, but I found that any Group 35 battery works perfectly fine/fits perfect w/no modifications needed.

Optima Red Tops are great as they require little to no maintenance and can be mounted in any position as there is no liquid to leak out. But in my experience, once the battery drains, Optima even states "DO NOT JUMPSTART". I found this damages the cells in the batteries and instead they really need to trickle charge fully recover.

I work with Optimas all the time as that's what the military went to to save money, but in the long run, the best batteries are the conventional types as they seem to be the most reliable. Just my $0.02