ethyl oleate

Pros - Reduces injection soreness, can make gear in higher mg/ml

Cons - Expensive.
I started using it to reduce injection soreness. For me it does NOTHING to reduce soreness. It is nice because it is thin. LL has it fairly cheap.
Everyone's different re: reduced inj site discomfort (big suprise) I haven't met too many who didn't notice at least a little bit of improvement with short ester inj like prop using EO as part or all of the carrier.

Personally, I like the fact that I can make 200mg/ml+ concentrations of acetate, propionate, and phenylpropionate esters with it.
pros - thinner, soreness is gone, higher concentrations
cons - price and low availability in europe