Engine and its systems
When visits to gas stations start rising without clear reason, one might wonder what changed. The weather and routes stay the same, yet fuel use climbs. A trip to the service may reveal that the staff chalks up the expense to everyday costs. Instead, a preliminary self check can simplify the later service visit and make conversations with the technician more productive.
The engine has two main trouble spots that boost fuel consumption: low cylinder compression and misaligned valve timing.
Low compression causes inefficient fuel burning, so more fuel is required. Compression should be measured, which is a straightforward check.
Valve timing is a touch more involved. Its correctness is judged by markings that vary with engine type. On modern engines, knocked-out marks typically trigger the Check Engine light.
The fuel delivery system can also push consumption higher, usually due to dirty fuel or air filters. Assess their condition and replace them if needed.
Another common culprit is low fuel pressure from the pump. Pressure should be read with a gauge, and decisions made based on the result. For modern port fuel injection vehicles, typical pressure is around 3.5 bar; for older models, about 3 bar.
To save money on spark plugs, service intervals still matter, and some savings occur when maintenance is performed at the station or by a qualified professional.
Dirty fuel injectors can also cause an improper spray pattern. A fuel system cleaner added during refueling might help, but a proper flush at a specialist service is preferred.
The engine management system often acts as a collecting point for malfunctions that raise fuel use. A sensor issue can push the engine toward higher consumption, and the Check Engine light often helps identify the problem early.
Tools like the ELM327 diagnostic adapter paired with a smartphone app can shed light on what happened. It is essential to replace spark plugs on schedule and always use parts approved by the manufacturer or trusted equivalents.
Low fuel pressure can prevent proper atomization of the injectors, further complicating efficiency.
An exhaust system with mechanical damage can also raise consumption, as it hinders the removal of exhaust gases.
The exhaust system increases consumption mainly by restricting exhaust flow. This can happen with dented pipes, loose baffles, or catalytic converter issues. A pressure gauge mounted in place of the first lambda sensor helps diagnose the issue. The back pressure should stay under about 0.3 bar, even at high engine speeds.
Cooling system problems that push operating temperatures away from the ideal range will affect fuel use. A simple thermometer may not be enough for reliable checks on all vehicles. Using an OBD adapter like the ELM327 can provide quick insight into cooling performance.
Transfer
The wear of a gearbox shaft bearing cannot be directly diagnosed by fuel use, though it adds friction and can raise consumption. Slippage in friction pairs also drives higher fuel use. This affects manual gearboxes, continuously variable transmissions, and hydromechanical clutches. In any case, continuing to drive with such defects risks more fuel costs and potential towing if the problem worsens.
Clutch wear, a failing torque converter, or a transmission slipping state can push both fuel use and transmission temperature higher. Thickened transmission oil can also contribute, as can a stiff front axle with a heavy drive setup.
Chassis and steering
Wheel misalignment clearly raises rolling resistance and fuel use. The remedy is straightforward: align the wheels properly and correct any issues.
Tire pressure matters. Underinflated tires waste fuel and reduce efficiency. Many manufacturers even recommend a touch higher pressure for highway driving.
Brake system
Parking and service brakes can nearly double fuel consumption if parts stay engaged or not fully released. It is important to check and adjust brake components when needed. Ongoing low tire pressure also hastens tire wear and worsens economy.
Overload and aerodynamics
Carrying excessive weight clearly raises fuel use because more energy is required to accelerate and to overcome rolling resistance. Aerodynamic drag plays a role too; racks, deflectors, and certain body modifications increase drag roughly with the square of speed.
Overloading a vehicle and poor aerodynamics together have a noticeable impact on fuel economy.
What else?
- A sporty driving style can push fuel consumption higher. Aggressive starts, heavy throttle use, and frequent hard overtakes leave little room for economy. Diagnosing the root cause may be more important than chasing low numbers.
- A cold engine or gearbox tends to burn more fuel, especially on short trips. The control system works hard to warm up, which can waste fuel during a city crawl. The best plan is to drive smoothly and allow the system to reach operating temperature quickly.
- Low-quality fuel can cause a gradual rise in consumption. If unusual engine behavior appears after a cheap fill, try refueling at a known, reputable station and use quality fuel. If the change persists, a diagnostic check is warranted.
FIREWOOD INSTEAD OF PETROLIn the early 1940s, a GAZ-42 truck powered by a gas generator journeyed from Moscow to Blagoveshchensk, covering 8400 km in 55 days using birch, oak, spruce, pine, larch, and reclaimed wood sleepers as fuel blocks. |
- Detailed instructions for reducing fuel consumption can be found here.
- Beyond the wheel offers insights on fuel efficiency in Telegram.