Re: how to clean oily salad dressing off trex deck
A tri-sodium-phosphate solution may help, I've had reasonable success with that, though the stain remained even though the oil was removed.
Steam may also help draw out the oil. I've been testing steam cleaners recently, and while I've not done this particular test, steam does clean and emulsify grease and oils well. Here are the machines that I've personally used and reviewed.
Ladybug XL 2300
SteamFast SF 275
SteamFast SF 246
Vapamore MR 100
I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!