The ornamental design for an engine, as shown and described.
FIG. 1 is a perspective view of the engine showing our new design, taken from the top, front and left side thereof;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a left side elevational view thereof;
FIG. 5 is a right side elevational view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The broken lines are for purpose of illustrating portions of the article that form no part of the claim. The surface is lined for contour only, and no claim is made to a particular texture. No claim is made to portions not shown in the drawings.