I have a very old premix 2 stroke and have been using seafoam for years and it seems to work great for me. I also add in the original sta-bil (red) on occasion if the fuel is not used right away. My question is should I upgrade to the new "Seafoam Pro Marine" & the newer "Sta-bil 360 Marine" (blue) or is it just more money for the newest supposedly better product? Your thoughts, Thanks.

If you are not burning ethanol treated fuel, it may not matter.

If you are, consider switching to Rec Gas. (non-Ethanol)

If Rec gas is not available, I'd switch.

A-Jay

What A-Jay said. The best fuel treatment is non-ethnol gas. I have a 1996 2 cycle and I use non ethanol gas but I still put a little Startron and Sea Foam in. I am not changing, if it ain't broke, don't try to fix it!!

There is a ton of information on here on fuel additives and whether they are needed , or not.  Do a search.  I have used E10 in my Yammie 60hp (I bought in 2000) since it hit the pumps and no fuel additives and never a problem. I keep the 21 gallon tank filled to the brim when not on the water and therefore no condensation.  I have all original fuel lines and bulb...no deterioration.