filler cap
From Longman Dictionary of Contemporary EnglishRelated topics: Motor vehiclesfiller capˈfiller cap noun [countable] British English TTCthe lid that fits over the hole in a car that you pour a liquid into, especially oil or petrolExamples from the Corpusfiller cap• All models have laminated windscreen, rear screen wash-wipe, clock, locking filler cap, cigar lighter and side mouldings.