IMO avoid at all costs
use the thinnest oil you can get, helps lube up all the parts quicker form cold..
i only say this because it cost £1400 repair my dads engine (3.0l v6 mitsy) after the use of it,
it ruined the hydraulic tappets that were unrepairable so new part had to be bought.
my dad thought the same as you he used slick50 thinking it would protect the engine, an engine that was 100k+ sweet sounding before and after the use of slick50 sounded like it a bag of nails in a biscuit tin,
the theory is if the oils is thick then the parts take longer to get oil because it takes longer to warm up so wear can occur from cold ,
if the oil is thin like synthetic oil then the oil gets to the parts quicker preventing the cold engine wear.. 😃 IMO.