Metalcloak IQ: Fuel Consumption Calculator
Enhanced Fuel Consumption Calculator
Calculate MPG impact from tire size and gearing changes
See how modifications affect your fuel economy - individually or combined
Complete Setup Calculator
Calculate the combined effect of changing both tire size and gear ratio. This gives you the most accurate picture of how your modifications will affect fuel economy.
Final MPG
With all modifications
Total MPG Change
Combined effect
RPM at 65 mph
Final engine speed
Extra Cost/Year
Additional fuel cost
Combined Impact Breakdown
Why Combined Calculations Matter
Gear Compensation: Many people install lower (numerically higher) gears when running larger tires to restore lost performance. This calculator shows how these modifications work together.
Net Effect: The combined impact isn't simply additive - larger tires make the effective gearing taller, while lower gears make it shorter. The net result determines your final RPM and fuel economy.
Sweet Spot: You can find gear ratios that minimize MPG loss while maintaining good performance with larger tires.
New MPG
With larger tires
MPG Change
Gain or loss
Extra Fuel/Year
Additional consumption
Extra Cost/Year
Additional fuel cost
Tire Size Comparison
New MPG
With new gears
MPG Change
Gain or loss
RPM Change
At 65 mph
Extra Cost/Year
Additional fuel cost
Gearing Comparison
Fuel Economy Impact Factors
| Modification | Typical MPG Impact | Primary Cause | Notes |
|---|---|---|---|
| +2" Tire Diameter | -2 to -4 MPG | Increased weight & drag | Varies by tire weight |
| +4" Tire Diameter | -4 to -7 MPG | Weight, drag, gearing | Consider gear change |
| Lower Gear Ratio | -1 to -3 MPG | Higher engine RPM | Better for larger tires |
| Combined Tire + Gear | Variable | Net gearing effect | Use Combined tab! |
| Lift Kit (2-4") | -2 to -4 MPG | Increased wind resistance | Cumulative with tires |
| Heavy Bumpers/Armor | -1 to -3 MPG | Added weight | Affects acceleration |
| Roof Rack/Lights | -1 to -2 MPG | Wind resistance | Speed-dependent |
Understanding Combined Effects
Why Combination Matters:
Tire & Gear Interaction: Larger tires effectively make your gearing taller (like going from 4.10 to 3.73 gears), while lower gear ratios make it shorter. The net effect determines your final performance and economy.
Common Scenarios:
- 35" tires + 4.56 gears: Often restores near-stock RPM with 31" tires and 3.73 gears
- 37" tires + 5.13 gears: Compensates for the larger tire's gearing effect
- Optimizing the balance: Find the sweet spot between performance and economy
Calculation Method:
The combined calculator uses the formula: Net Gear Ratio = (New Gear Ratio / Stock Gear Ratio) × (Stock Tire Diameter / New Tire Diameter)
This gives you the true effective gearing change when both modifications are made together.
Fuel Economy Tips:
- Use the Combined tab: Most accurate for tire + gear modifications
- Tire Pressure: Keep at proper pressure - underinflation kills MPG
- Weight Management: Remove unnecessary gear when not needed
- Driving Style: Gentle acceleration and steady speeds help
- Maintenance: Clean air filter and regular tune-ups
- Balance: Consider if MPG loss is worth capability gains
- Real-World: Your actual results may vary from calculations