A truck, comprising: - a first fuel tank, comprising a first orifice for housing a fuel level sensor for measuring a fuel level in a fuel supply system of the truck; - a second fuel tank, arranged in fluid communication with the first fuel tank, and comprising a second orifice formed identically to the first orifice; and - an injection mouldable sealer cap, mountable to the second fuel tank for sealing the second orifice, wherein the injection mouldable sealer cap comprises: ∘ a cover plate, arranged for covering the second orifice; characterized by ∘ a tubular insert, coaxially extending from the cover plate and arranged for extending into the second orifice, wherein the tubular insert comprises an outer wall provided with a locking arrangement that is engageable with an inner wall structure of the second fuel tank to clamp the cover plate, by applying a sealing force between the second fuel tank and the injection mouldable sealer cap; wherein the locking arrangement is lockable by a rotation of the injection mouldable sealer cap in a sealing direction; wherein the cover plate comprises a top surface provided with a plurality of circular groove segments; wherein each groove segment of the plurality of groove segments provides a contact surface, substantially normal to the sealing direction, wherein the contact surface is accessible by a mounting tool for rotating the injection mouldable sealer cap in the sealing direction to apply the sealing force; and wherein each groove segment of the plurality of groove segments provides a bottom surface that extends against the sealing direction from the contact surface towards the top surface, wherein the bottom surface comprises an inclining wall section that inclines from a lower level inside the groove segment towards the top surface, for dislocating the mounting tool from the injection mouldable sealer cap when rotated against the sealing direction. - a first fuel tank, comprising a first orifice for housing a fuel level sensor for measuring a fuel level in a fuel supply system of the truck; - a second fuel tank, arranged in fluid communication with the first fuel tank, and comprising a second orifice formed identically to the first orifice; and - an injection mouldable sealer cap, mountable to the second fuel tank for sealing the second orifice, wherein the injection mouldable sealer cap comprises: ∘ a cover plate, arranged for covering the second orifice; characterized by ∘ a tubular insert, coaxially extending from the cover plate and arranged for extending into the second orifice, wherein the tubular insert comprises an outer wall provided with a locking arrangement that is engageable with an inner wall structure of the second fuel tank to clamp the cover plate, by applying a sealing force between the second fuel tank and the injection mouldable sealer cap; ∘ a cover plate, arranged for covering the second orifice; characterized by ∘ a tubular insert, coaxially extending from the cover plate and arranged for extending into the second orifice, wherein the tubular insert comprises an outer wall provided with a locking arrangement that is engageable with an inner wall structure of the second fuel tank to clamp the cover plate, by applying a sealing force between the second fuel tank and the injection mouldable sealer cap; wherein the locking arrangement is lockable by a rotation of the injection mouldable sealer cap in a sealing direction; wherein the cover plate comprises a top surface provided with a plurality of circular groove segments; wherein each groove segment of the plurality of groove segments provides a contact surface, substantially normal to the sealing direction, wherein the contact surface is accessible by a mounting tool for rotating the injection mouldable sealer cap in the sealing direction to apply the sealing force; and wherein each groove segment of the plurality of groove segments provides a bottom surface that extends against the sealing direction from the contact surface towards the top surface, wherein the bottom surface comprises an inclining wall section that inclines from a lower level inside the groove segment towards the top surface, for dislocating the mounting tool from the injection mouldable sealer cap when rotated against the sealing direction.