The spark plug gap for the 2012 Dodge Ram 1500 with a 5.7-liter Hemi is typically 0.040 inches (1.0 mm).
Factory specification and what it means
In most factory service documents and common replacement plug guides, the recommended gap for the 5.7 Hemi is 0.040 inches. This applies to factory-correct copper, platinum, and iridium plugs used in the 2012 Ram 1500. Maintaining this gap helps ensure proper ignition timing, efficient combustion, and optimal engine performance.
Common gap values you might encounter when replacing spark plugs on this engine are listed below.
- 0.040 inches (1.0 mm) — standard and most widely recommended gap for factory and aftermarket plugs.
- 0.043 inches (1.09 mm) — acceptable only if the plug manufacturer specifies it for the particular plug type you are using.
Sticking to the 0.040-inch gap is advised unless your chosen spark plug manufacturer explicitly specifies a different gap for their product.
Choosing the right spark plugs for a 5.7 Hemi
Most replacement plugs for the 5.7 Hemi are gapped to 0.040 inches out of the box. If you’re choosing aftermarket plugs, always confirm the recommended gap from the plug manufacturer, and adjust only if they specify a different size.
- Copper plugs — commonly gapped to 0.040 inches.
- Platinum or iridium plugs — typically pre-gapped to 0.040 inches; verify with the manufacturer.
- High-performance or specialty plugs — may list 0.043 inches as acceptable; follow the manufacturer’s guidance.
When in doubt, rely on the plug manufacturer’s instructions and the vehicle’s service manual to ensure compatibility with your engine and its ignition system.
How to check and set the gap
If you are replacing spark plugs, it’s important to verify the gap before installation. Follow these steps to ensure accuracy.
- Remove the new spark plug from its packaging and inspect for any damage.
- Use an appropriate spark plug gap tool (wire-style or disk-style) to measure the gap across the ground electrode.
- If the gap is not exactly 0.040 inches (1.0 mm), carefully adjust the gap to the specified size using the tool.
- Re-check the gap, then install the plug and torque to the manufacturer’s specification. If the plugs were pre-gapped by the manufacturer, do not re-gap unless the tool indicates a deviation from the specified size.
Accurate gap ensures reliable starting, smooth idle, and optimal combustion, contributing to mpg and emissions performance.
Summary
For a 2012 Dodge Ram 1500 equipped with a 5.7 Hemi, the standard spark plug gap is 0.040 inches (1.0 mm). Use this as the default when installing factory or aftermarket plugs, but always follow the specific guidance of the plug manufacturer and the vehicle’s service manual. Verify the gap with a proper gauge before installation to avoid misfires and reduced performance.