"The cook has oil in the plate."
Translation:Il cuoco ha l'olio nel piatto.
Nello is a compound of in+lo, and nel of in+il, so apply the rules you use to decide between il and lo :)
Hi Formica, to me is still a bit confused when to use "il" and when to use "lo", can you clear this doubt, please?!?
As an article, lo is used before some combinations of letters (no matter what word they belong to), the most notable ones being z+vowel, s+consonant, i+vowel, gn, pn and ps.