There is a lot of things that can be done to reduce fuel consumption of a car. Decreasing the rolling resistance coefficient, choosing the right oil, lightened materials, aerodynamic drag coefficient can be modified for reducing fuel consumption.
1) Decrease the rolling resistance coefficient for fuel savings
First, the rolling resistance coefficient (Cr) can be reduced by:
- Increasing the tires’ inflation pressure up to 3 bars (43 psi). The trade off is a harsher ride.
- Choosing tires with the lowest rolling resistance, such as Goodyear EfficientGrip Performance, Dunlop BluResponse, Hankook Kinergy Eco or Michelin EnergySaver+.
- Using worn tires: rolling resistance decreases along the tires’ wear. The trade off is a reduced grip on wet roads.
2) Choose right engine oil to reduce fuel consumption
Next, an oil with a broader viscosity index will reduce engine friction. If the current oil is 10W40 (or worse, 15W40) do an oil change with 5W30, 0W40 or 5W40, depending on what is allowed by the car manufacturer.
3) Using light materials can save considerable fuel
A car can be lightened by throwing out everything that’s not needed, such as passenger seats, carpets, etc! Every 100 kg of load increases fuel consumption by an average of 0.2 – 0.3 l/100 km, depending on driving conditions.
Those are easy and cheap mods. If you are willing to spend a lot of money, you can swap the transmission for one with numerically lower overall ratios, so that the engine will rev slower at a given vehicle speed. If it’s a rear wheels drive, the axle ratio may be changed while keeping the same gearbox.
4) Modify aerodynamics to reduce fuel consumption
The aerodynamic drag coefficient (Cd) can be improved by accessories such as spoilers. If you drive in cold temperatures, the cooling air intake area in the front grill can be reduced. Lowering the suspension will also reduce the Cd, but the trade off is a reduced ground clearance, specially when loaded.
Next, you can modify or swap the engine for a more efficient and less powerful one… but these are major modifications to reduce fuel consumption.