I'm not aware of any engine issues with the SL55 engines, the M113K is probably one of the most reliable engine MBZ has built. The 2009 SL63 (M156) had the headbolt issues breaking for the pre 2011 or so model. The benefit of the 63 would be a much much faster gearbox, and the updated looks interior goodies. I was about to get a 63 because i like the updated look, after reading about it, and finding out you can't really squeeze any power out of it like you can with a supercharged or turbo'ed engine, i went with an SL600.

 

I would avoid the SL63. In addition to head bolt issues, the M156 engine also had problems with the lifters. None of this was fixed until around MY2011, and the R230 ended production before that was fixed (even though it's last year was a MY2012). I also prefer the MY2009+ facelift. There should be plenty of MY2009+ SL550s to choose from. Facelift SL600s are very rare. I think there is only one for sale in all of the USA right now.

 

Thank you guys for responding. I have decided to keep it simple and take it easier on my wallet and go for the SL550 09+
UNLESS I can find a good deal on a SL55 preface lift... the 2008 I am considering is about $30,000 CAD or $24,000 USD.
I feel like that's a bit much given the higher mileage but I suppose they hold their values since not too many were made