1. Comparing Specifications: Different Units, Different Outputs

The manufacturer-listed figures for the two G AMT variants highlight a few core differences:

Specification Petrol G AMT E-CNG G AMT Key Difference
Fuel Economy 24.77 km/L 34.47 km/kg (in CNG mode) Uses different fuel units (litres vs. kilograms)
Max Power Output 61 kW 51.3 kW (CNG mode) / 61 kW (Petrol mode) ~16% drop in rated power when running on gas
Transmission 5-speed AMT 5-speed AMT Identical transmission across both versions

(Note: Fuel economy figures are official Toyota claims from printed documentation, not independent road-test results.)

2. Calculating Your Fuel-Only Break-Even Point

Because petrol is sold in litres (₹/L) and CNG in kilograms (₹/kg), you cannot compare mileage claims directly. Instead, calculate your break-even distance using real local prices and on-road quotes:

Step 1: Determine Fuel Cost Per Kilometre

  • Petrol Cost per km: Local Petrol Price (₹/L) ÷ 24.77

  • CNG Cost per km: Local CNG Price (₹/kg) ÷ 34.47

  • Per-Kilometre Saving ($S$): Petrol Cost/km − CNG Cost/km

Step 2: Calculate Break-Even Mileage

  • On-Road Price Delta ($\Delta$): CNG On-Road Quote − Petrol On-Road Quote

  • Break-Even Distance: On-Road Price Delta ($\Delta$) ÷ Per-Kilometre Saving ($S$)

How to Interpret the Result:

  • Expected Mileage > Break-Even Distance: If your planned total driving distance comfortably exceeds this number, the lower fuel costs of CNG will recover the upfront price premium.

  • Expected Mileage < Break-Even Distance: If you drive low annual miles or plan to sell the car early, fuel savings won't offset the higher purchase price. In this scenario, the Petrol G AMT is the more sensible financial choice.

(Note: This calculation provides a baseline fuel-cost model. It does not account for petrol used during cold starts, maintenance cost variations, insurance differences, or resale value.)

3. Practical Trade-Offs to Test Before Buying

A favorable payback calculation is only part of the equation—daily usability matters just as much:

Power Output in Daily Driving

The bi-fuel engine delivers its full 61 kW when running on petrol, dropping to 51.3 kW in CNG mode. During your test drive, switch to gas mode with a normal passenger load to ensure the lower power output meets your expectations for highway passing and city driving.

Refuelling Convenience

Consider your daily routes and the availability of CNG stations. Long queues or out-of-the-way detours to refuel can offset the monetary savings over time.

Boot Space Usability

While official volume figures for the G AMT CNG variant aren't published separately, the CNG tank takes up space in the rear cargo area. Take your usual family luggage or strollers to the dealership to test practical fit before placing an order.

Summary: Which Should You Choose?

  • Choose Petrol G AMT if: You drive lower annual mileage, plan a shorter ownership period, lack convenient CNG refuelling along your routes, or prefer consistent 61 kW power delivery at all times.

  • Choose E-CNG G AMT if: You are a high-mileage driver whose calculated break-even point occurs well within your planned ownership period, have easy access to local CNG stations, and accept the slight power reduction in gas mode.