i kinda know how to do seafoam, but i have one question i have a older model blazer i have a 1989 s-10 blazer and i was wondering if i should use seafoam? will it hurt anything or is it a good thing that i do it. ever since my brother got it the truck we havnt put any kind of liquids in it(liquids such as fuel addetives and cleaners) we have had the truck for about 6 years or so.

 

I would go with a normal injector cleaner over seafoam. Also remember if you do add any thing it will help loosen all that build up and might cause issues to show up. I'd say if its running fine then leave it be.