NGK M157 One Step Colder Spark Plugs
$175.00
Best for: Tuned M157 5.5 biturbo (Stage 1–2), towing/track, hot climates.
Gap guide: 0.024–0.026″ (91–93) • 0.022–0.024″ (higher boost/E blends). Tune/logs decide.
Notes: One heat range colder than typical OE; helps reduce high-load misfire. VIN fitment check recommended.
Description
Why a Step-Colder Plug on M157
- Handles elevated combustion temps from increased boost/timing
- Reduces risk of spark blowout at richer λ and higher airmass
- Improves repeatability for back-to-back pulls or hot-soak conditions
Recommended Gap
- Stage 1 on pump gas: 0.024–0.026″
- Stage 2 / E blends / higher boost: 0.022–0.024″
If you see misfire counters increment in high gear/high load, close the gap by ~0.001–0.002″. If idle is rough on cold mornings, you can open slightly within the ranges above.
Fitment (M157 examples, can also fit M278)
E63/CLS63 (W212/W218), ML/GL/GLE/GLS 63 (W166/X166), S63 (late W221/early W222), and other 5.5L biturbo variants. Send VIN to confirm exact plug and coil supersessions.
Install & Torque
- Torque: follow OE; typical for M14 gasket-seat plugs is ~17 lb-ft.
- Dielectric grease inside coil boots only; keep electrodes dry/clean.
When to Replace
Tuned use: inspect at 10–12k mi, typically replace by 12–15k mi. Track/heavy use may require shorter intervals. Look for eroded center electrode, glazed insulator, or widened gap.
FAQ
Do colder plugs hurt cold starts?
Yes, cold starts are typically a bit rougher. In cold weather if cold idle is fussy, open the gap slightly within the recommended range.
Misfire after install?
Re-check gap, coil connectors, and re-torque to specs of 17 pound-feet. Scan for codes and review logs; if misfire persists, swap coils/plugs cylinder-to-cylinder to isolate.
One-step colder plugs are designed to dissipate heat more efficiently, which will bring down combustion chamber pressures and prevent pre-detonation.
These plugs are highly recommended for modified engines or engines undergoing extra modification soon.
These plugs are not recommended for stock or close-to-stock power vehicles because the cylinder temps do not get hot enough, which can cause carbon buildup on the plugs.
Set of 8
