Re-stain advice requested

I am planning to re-stain a dried out 20 year old deck that was last successfully sanded and stained with 2 coats of Cabot's Australian Timber Oil  5 years ago.  I have read on your site that the Cabots product has changed, so I do not want to use it again.   The deck sits lakeside in mostly full sun for half the day in the mountains of Massachusetts.  During the winter, it is completely covered with several feet of snow.
I do not know if it was constructed of cedar or pressure-treated wood. If this is critical to deciding the stain, can can you advise me on how I can figure this out? 

What would you recommend for each type of wood ( cedar or pressure-treated wood) ? I can try to have my contractor identify the wood type for me. 
Thanks.