Learn the best time to shift gears in a diesel car for optimal performance and fuel efficiency. Discover tips on when to shift gears and maximize your driving experience.
There is no doubt that the manual gearbox is living its last years among us. The vast majority of new vehicles coming onto the market come with automatic transmissions. And it is not that these gearboxes are better or worse. Simply, because they are more efficient, they have fewer approved emissions. Manufacturers are simply adapting to the agenda.
Those of us who like to drive tend to be a bit indifferent to the type of gearbox a car has. Although, if possible, we will almost always choose a manual transmission. And when it comes to manually operating the transmission, the least we can do is do it well. In this article we will explain step by step how to change gears perfectly in a car with a diesel engine .
Is there a rule for shifting gears?
There are hundreds of TikTok videos, as well as blog posts, explaining rules for shifting gears . One of the most well-known is the “20 km/h rule,” which says that we can shift up a gear after exceeding a multiple of 20. According to this rule, we could go up to 20 km/h in first gear, up to 40 km/h in second, 60 km/h in third… and so on.
However, that rule is nowhere near correct . While it works in the city, when you hit the open road and face a tricky overtake or a hill climb, you’re going to run out of power, other drivers are going to honk at you, and you’re going to have a pretty bad time behind the wheel.
What you need to understand before we get into the subject is that there is no one way to change gear . It all depends on the driving you are doing. You cannot drive the same way on a motorway as you do on a two-way national road. Nor should you hold the same gear at 90 km/h on a dual carriageway as you do on a country road with a very steep climb. And this applies to both diesel cars and those that run on petrol.
Understanding a Diesel Car Tachometer
A while ago we wrote a rather interesting article about what car engine torque is and how it is calculated. Almost everything we are going to explain in this section has a lot to do with what we learned in those lines.
Every diesel car is different. There are cars that can pull like beasts at 1,500 RPM, and others that can be completely dead at 2,000 RPM. You’ll push the pedal to the metal, and the car won’t react at all.
Diesel vehicles are characterized by delivering their maximum torque in a low range on the tachometer . This makes them somewhat easier to drive in difficult situations. For example, a 2014 Audi A4 2.0 TDI 150 hp delivers its maximum torque between 1,750 and 2,500 rpm. As we mentioned in the article we linked earlier, the maximum torque is that zone in which the cylinders are perfectly filled and perfect combustion occurs. The most efficient driving will always be in that range of revolutions.
The other issue is the maximum power . Diesel engines, working with a higher compression, cannot turn as much as gasoline engines, a design issue. That is why the maximum power is also produced much earlier. Continuing with the same Audi, this German sedan that we have chosen as an example gives its maximum power when the needle touches 4,200 RPM. The engine can even turn more if we take the needle to the red zone, but we will be burning fuel in vain, since we will not gain more power.
When should I change gears with my diesel car?
As we have been saying, each diesel engine has its own particularities, so we cannot give you a single figure as an answer. What you can do is understand the specification sheet of your car and adapt the gear shifting based on the engine design and the type of driving you are doing.
We explain it to you in four different situations , which are the following:
City driving
In the city, we are always interested in saving fuel . Combustion cars consume much more fuel in urban cycles. This seems counterintuitive, but what happens is that the engine is not efficient when making constant starts and stops .
In the city, it is therefore best to drive in the highest gear that each situation allows. In the specific case of a diesel vehicle, it is not even necessary to reach the maximum torque zone of the engine . You can shift up a gear when you reach around 1,500 revolutions per minute. However, if you notice that your car jerks or tries to stall when shifting up a gear, try shifting a little higher in the rev range.
Standard driving on highways and motorways
Diesel cars are great for long road trips, especially at high speeds. The gearboxes typically fitted to cars with a mid-size engine – such as the 2.0 TDI in the Audi example above – are designed to allow the car to cruise at 100-120 km/h on the flat at a speed where the rev counter is in the maximum torque range (2,200 RPM in our example). After all, we want the car to respond well to the accelerator, but with efficient fuel consumption .
If you’re joining a motorway, it’s best not to shift gears as quickly as you would in the city. You can shift gears much longer, optimising the maximum torque zone more . This way, you can benefit from more progressive acceleration and you’ll be able to make quicker manoeuvres. If you’re not sure what speed range your car delivers maximum torque at, look for a fact sheet on the Internet. It’s fairly easy information to find.
Driving on roads with slopes and curves
Now let’s move on to a less relaxed scenario. A country road with changes in elevation, curves and cars driving in the opposite direction. You can change gears early and save a lot of fuel, yes. But you won’t have complete control of the vehicle .
On a road like this, we don’t want to be driving in high gears . We want to play with the gearbox to keep our engine in a wider range of revs. When approaching a curve, we must brake, downshift and approach the curve in such a way that we can accelerate correctly after having passed it. The same thing happens when approaching a slope. For this reason, it is not unreasonable to drive in a lower gear, and in the highest part of the maximum torque zone .
Also, at critical moments, such as when overtaking, we do not want to change to a higher gear. The ideal is to push the revs as far as possible to the maximum power zone , so that we can make the manoeuvre quickly and safely.
Sporty driving
Finally, we have sporty driving . It may sound like an oxymoron to practice this type of driving in a diesel car. However, it can be done.
When we talk about sporty driving, we are referring to a type of driving that demands a lot from the machine . It can be practiced on normal roads as long as the highway code is respected. However, the ideal is always to practice it on circuits or private sessions.
In this scenario, it is best to always point the tachometer needle towards the power line . This is when we will shift into the next gear. By doing this, we will achieve the acceleration figure approved by the manufacturer – 0 to 100, that is.
When it comes to downshifting, the same thing happens. We are not interested in tackling a curve or a slope in a gear that is too high, because the engine revolutions will fall to a point where the accelerator pedal will not respond as we want . That is why it is so important to downshift and even practice some other rev-matching techniques such as heel-toe or double clutching.