MAHLE S42140.040 Premium Plasma-Moly Piston Ring Set +.040" Bore Single Cylinder

The MAHLE S42140.040 is a premium plasma-moly piston ring set engineered to OE specifications for a 4.253-inch (+.040" overbore) cylinder. Designed as part of MAHLE's Original line, these rings are built to deliver factory-level performance and exceptional durability, making them a trusted choice for professional engine builders and serious rebuilders alike. This listing is for a single cylinder set; order quantity 6 for a complete engine rebuild.

Ring Specifications:

• Bore Size: 4.253 in. (108.026mm) — +.040" overbore
• Top (Compression) Ring: 2.87mm thickness | Ductile iron | Plasma-moly facing
• Second (Intermediate) Ring: 2.5mm thickness | Cast iron | Chrome facing
• Oil Control Ring: 3.45mm thickness | Iron | Standard tension
• File Fit: No | Gapless: No | Gas Ported: No
• Sold as: Single cylinder set (qty 6 required for full 6-cylinder engine)

Key Features:

• Pre-lapped design seats immediately upon installation, virtually eliminating break-in time
• Plasma-moly top ring facing provides superior wear resistance and reduced friction
• Barrel-faced compression ring contact area delivers more efficient compression and CNC-controlled gap chamfer reduces blow-by
• Reverse twist intermediate ring design enhances groove side sealing with taper-race machining for improved cylinder wall contact
• CP-20 oil ring assembly features an exclusive 20-degree ear angle for optimal side sealing against the cylinder wall, plus a special chemical polish on the expander for enhanced oil drain-back
• Ring materials, coatings, and tension levels are all application-optimized for reduced friction and extended service life

MAHLE is one of the world's largest OE piston ring manufacturers, and the S42140.040 reflects that expertise — delivering a drop-in replacement that meets or exceeds original factory tolerances. Whether you're rebuilding a worn engine or freshening up a high-mileage diesel, these rings provide a reliable, installer-friendly solution with no special fitment procedures required.