The Classic Mini fuel tank is mounted beneath the boot floor and secured by a mounting strap bolted to the underside of the car. Two tank capacities were fitted across production: a smaller 5½ gallon tank used on some base trim models from 1976 to 1980, and the standard 7½ gallon tank fitted to all other models throughout the remainder of production. The 7½ gallon tank itself comes in several specifications depending on the fuel system fitted to the car, and ordering the correct tank requires knowing which fuel system your Mini has, carburettor, SPi or MPi.
Tank Variants by Fuel System
Carburettor models use tanks with either an unrestricted or restricted filler neck depending on date and whether the car was originally specified for leaded or unleaded fuel. All models from 1976 to 1980, and all leaded fuel models from 1980 onwards, use an unrestricted neck tank. Unleaded 998cc models and the 1275cc Cooper carburettor (1990 to 1991) use a restricted neck variant, as do non-Cooper 1275cc carburettor models (1992 to 1994). Fuel injection models (both SPi and MPi) require specific tank variants to accommodate the in-tank electric fuel pump and revised fuel feed arrangements, injection tanks are not interchangeable with carburettor tanks.
Some limited edition models, including the Paul Smith edition, used uniquely finished tanks. Japanese export models also have specific tank requirements depending on whether the car is SPi or MPi specification.
Sender Units
The fuel tank sender unit provides the fuel level reading to the dashboard gauge. Carburettor models and fuel injection models use different sender units, this is not a cosmetic difference but a fundamental one. On fuel injection cars, the sender unit assembly also incorporates the in-tank electric fuel pump, making it a more complex and heavier component than the simple float-arm sender used on carburettor models. The sender unit is secured to the tank by a locking ring and sealed with a rubber gasket.
Both the locking ring and seal should be replaced when fitting a new sender unit to ensure a reliable, leak-free seal, reusing an old gasket is a common cause of fuel smell and seepage from the sender area.
Fuel Caps and Filler Seals
Both locking and non-locking fuel caps are available in stainless steel and black finishes. Fuel injection models require a specific locking cap designed for the injection system’s pressurised fuel return arrangement. The filler neck seals, both through the back panel and inside the back panel, should be inspected and replaced if deteriorated, as failed seals allow water ingress into the boot area and fuel fumes into the cabin. The 5½ gallon tank does not use the inner seal.
E10 Compliance
All replacement fuel tanks supplied through the MGOC Spares Classic Mini range are E10 compliant, suitable for use with current UK ethanol-blended petrol. For optimum performance and protection, owners of carburettor Minis should fill with 97+ Premium Unleaded E5 rather than standard 95 E10. For detailed guidance, see our blog Using Ethanol-Blended Petrol in Your Classic Car.
MGOC Spares Range
The MGOC Spares Classic Mini fuel tank range covers replacement tanks for all variants including 5½ and 7½ gallon capacities, carburettor and injection specifications, sender units for carburettor and injection models, locking rings, sender seals, fuel caps in locking and non-locking types, filler neck seals, tank mounting straps, drain plugs, protection plates and all associated fixings.