AutosDownshifting before accelerating: A key to engine longevity and safety

Downshifting before accelerating: A key to engine longevity and safety

Downshifting before accelerating is good for the engine and improves safety.
Downshifting before accelerating is good for the engine and improves safety.
Images source: © Photo by Autokult.pl
Szymon Jasina

22 June 2024 13:31

Good driving techniques can lead not only to fuel savings but also to reduced vehicle wear and tear. However, even experienced drivers can make mistakes due to bad habits. One of these is failing to downshift before accelerating.

An empty road, a car with decent performance, and the need to overtake a slower vehicle. In such situations, drivers do not always decide to downshift before accelerating, assuming they have enough time and space for the manoeuvre and that the car will accelerate sufficiently when the accelerator pedal is pressed to the floor. However, this is a mistake that adversely affects the engine.

Drivers also mistakenly believe that accelerating at lower revs is more beneficial because it generates less noise from the exhaust system. However, it should be remembered that a high load at low revs is not advisable for the engine. In such operating ranges, the engine works less efficiently, which means that more energy from the fuel is used to generate heat rather than acceleration. This results in higher fuel consumption and engine overheating, especially the internal parts of the cylinders.

Overheating leads to uneven combustion of the fuel-air mixture and ignition problems. As a result, forces in the cylinder are distributed unevenly, accelerating engine wear. This is particularly detrimental to turbocharged engines, which are standard in modern cars. It also increases the risk of pre-ignition of the mixture.

Two Japanese companies, Toyota and Denso, a manufacturer of spark plugs, have studied the issues arising from accelerating without downshifting. Research has shown that in such cases, glowing fuel and oil residues may remain in the engine, which at low revs are more likely to cause pre-ignition. This, in turn, leads to faster wear of pistons and spark plugs.

The necessity of downshifting before accelerating is also emphasised during driving courses. Overtaking is a dangerous manoeuvre that requires dynamic and rapid completion. Therefore, downshifting is crucial to maximise the car's acceleration and safely and quickly overtake a slower vehicle.

Related content