Plastic insert, urea tank and plastic oil tank

The utility model discloses a plastic insert, a urea tank and a plastic oil tank. The plastic insert comprises an insert main body, an insert convex rib, an insert concave rib and an insert rubber coating structure used for rubber coating assembly. The first side and the second side of the insert main body are oppositely arranged, the first side of the insert main body protrudes outwards to form the insert convex rib, the insert convex rib is arranged on the first side of the insert main body in an extending mode, the second side of the insert main body sinks inwards to form the insert concave rib, and the insert concave rib is arranged on the second side of the insert main body in an extending mode. The insert concave rib is arranged on the second side of the insert main body in an extending manner, so that the plastic insert disclosed by the embodiment of the utility model is higher in structural strength; the side, away from the insert main body, of the insert convex rib is larger than the side, close to t