whats the best fluid for long lasting Lps.

I agree with Rushton that a good cleaning is all that is really needed. (But what constitutes a "good" cleaning is a whole other discussion!) The environment is inherently dirty with dust etc. so using a preservative will just "preserve" in the grime that you didn't remove. I prefer to not have anything between me and the grooves!

I strongly urge the original poster to do a thorough search through the archives.

There are many ideas about what is ideal and the best, shared by a variety of posters.

Record Research Super Wash and Deep Cleaner, for the really dirty ones. A little goes a long way.