2005 GMC Sierra 2500 HD 2WD CNG MPG & Specs — Real Fuel Cost
Quick answer
The 2005 GMC Sierra 2500 HD 2WD CNG gets an EPA-estimated 8/11 MPG (city/highway) and 9 MPG combined, with an estimated $4,950/year fuel cost and 781.111 g/mi CO₂. Engine: 6 L 8-cyl.
The 2005 GMC Sierra 2500 HD 2WD CNG with the 6-liter 8-cylinder natural gas engine returns an EPA-estimated 8 MPG in the city and 11 MPG on the highway, for a combined 9 MPG. This page summarizes the official EPA fuel-economy and emissions data for this configuration.
| Engine | 6 L 8-cyl |
| Transmission | Automatic 4-spd |
| Drive | Rear-Wheel Drive |
| Fuel type | Natural Gas |
| Vehicle class | Standard Pickup Trucks 2WD |
| MPG — city | 8 |
| MPG — highway | 11 |
| MPG — combined | 9 |
| Annual fuel cost* | $4,950 |
| CO₂ tailpipe | 781.111 g/mi |
| EPA GHG score | — |
How efficient is it?
With a combined 9 MPG, the 2005 GMC Sierra 2500 HD 2WD CNG sits in the low range for fuel economy. That is roughly 49% thirstier than the typical Standard Pickup Trucks 2WD of its era (18 MPG class average) — expect higher fuel bills than class-average alternatives.
Fuel economy and running costs
At about $4,950 per year in fuel (EPA estimate, 15,000 mi/yr), fuel is a major part of the cost of owning the 2005 GMC Sierra 2500 HD 2WD CNG. Over five years that is roughly $24,750 at today's prices — before insurance, maintenance, and depreciation.
Emissions
The 2005 GMC Sierra 2500 HD 2WD CNG emits approximately 781.111 grams of CO₂ per mile at the tailpipe. Lower emissions generally track higher fuel economy.
How to read these numbers
EPA figures come from standardized laboratory test cycles and are the same estimates shown on the vehicle's window sticker. Your real-world mileage depends on driving style, conditions, fuel grade, and maintenance. Use combined MPG and annual fuel cost to compare vehicles fairly.