"J'ai de l'huile."
Translation:I have oil.
I am confused about this too. Is it a case that whenever "de" is used we have to assume it takes presidance over "l'"?
That would be: J'ai l'huile. The presence of "de" changes the meaning of he sentence to either "I have oil" or "I have some oil"
Du l'huile does not even exist. You have only "du, de la, de l' ". 'Du' is used for masculine nouns, 'de la' for feminine and 'de l' for elided masculine and feminine nouns. You have all this in FOOD Tips & Notes