Now and then, you can stumble across a discussion on auto enthusiast forums about whether the number of cylinders can influence engine life. Specifically, there is the suggestion that more cylinders make the engine last longer. It is based on the assumption that the larger number of cylinders leads to each of them firing less often and therefore serving longer. Some people even made it a routine to purchase used cars, calculating the effective working life of the engines in dependence to their cylinders (in the format "so many miles per each cylinder"). Is there any truth to this and how the number of cylinders corresponds with the engine’s durability?
More Cylinders versus Fewer Cylinders
Let’s start from the fact that in the most common 4-stroke engines each working cycle covers 2 turns of the crankshaft (which corresponds to 4 piston strokes) and each cylinder fires every two rotations. This means that provided the RMP of the engine is the same; they will deliver the same number of fires no matter how many cylinders each of the engines have. So, this cannot make your 4, 6 or 8-cylinder engine last longer or vice versa.
It’s another matter that a larger number of cylinders provides smoother torque increase and more power within the same engine displacement. The second can be related to engine life, for example, when speaking of larger and heavier vehicles. A heavy vehicle with small engine displacement (which depends on the total of all its cylinders’ volume) implies a higher load on the engine, which will work at ten tenths to move the vehicle around. Obviously, in this case, you can expect the faster wear and tear.
So, if there is a car presented in two options with different engine volumes and a different number of cylinders, it makes sense to opt for the version with more cylinders. It is especially true for vehicles with automatic transmissions and modern climate control systems since they can steal a decent amount of power.
However, this refers only to those cars whose engine capacity to weight ratio looks doubtful. Fortunately, nowadays they are not very common. Besides, a greater number of cylinders comes with a greater number of parts like spark plugs, valves, pistons and so on. Each of them adds weight to your engine, which in turn adds weight to your car, which in turn needs a more powerful engine to carry this weight. Sounds like going round in circles, doesn’t it?
Moreover, all these parts move back and forth, open and close, rotate and rub – and thus they are subject to wear. The more cylinders your engine has, the higher the risk that some of these parts will break and you will need to replace them. From this perspective, more cylinders don’t seem to prolong your engine life but may be seen as extra aches and pains. In particular, the four-cylinder engine has about one third fewer parts than the six-cylinder motor of the same displacement and capacity. Correspondingly, it requires less time for maintenance and repair, which is why I4 motors are widely used in low-end cars, where mechanical simplicity is more important than power or comfort.
Number of Cylinders versus Their Configuration
So, what do we get? Theoretically, if the engine of a certain volume is divided into 8 cylinders, instead of 4, then we get cylinders of smaller volume, which are easier to fill with air-fuel mixture and which have lighter pistons to pump inside of the cylinders. This leads us to decreased noise and vibrations, as well as better durability and higher RMP. However, in practice, there is such a thing as engine balance, and we know that these vibrations (and engine lifespan) depend on a cylinder configuration rather than exclusively on a number of cylinders.
For example, inline-four engines cannot boast inherent balance, but they are durable due to their simplicity. Flat-four engines are better balanced, yet more complicated. Can we say that both these engine types are equal, just because each of them features four cylinders? Nope. Then, maybe, V8 is better than I6, just because it has two more cylinders? We don’t think so. So, the bottom line is that different multi-cylinder engine designs have many variables including the choice of rings and their interference, cylinder material and lubrication, cooling, and many other factors apart from the number of cylinders and even their configuration.
Do More Cylinders Extend Engine Lifetime?
Let’s put this in a nutshell – all other things being equal, more cylinders are better since:
- Smaller and lighter parts can move faster by providing higher redline.
- More cylinders feature better power overlap and ensure smoother power delivery.
- These engines are less noisy and sound better.
- They tend to vibrate less due to lighter pistons.
- They generate more power for the same engine size.
However, all other things being equal, fewer cylinders are better since:
- Fewer parts mean lower cost.
- These engines have less things to break.
- With a limited number of parts, they boast less mechanical friction and require less oil for bearings, thus being more efficient.
So, it seems that any choice is a kind of compromise, but you really shouldn’t select a car based only on how many cylinders it features. Actually, the lifespan of your engine will depend on manufacture quality, your driving style, maintenance habits and other factors that have nothing to do with the number of cylinders. To this end, it makes sense to refresh good driving habits on Driver-Start.com, where both local driver’s handbooks and online tests can be found. Meanwhile, keep in mind that there is a worldwide tendency to fuel economy and thus to the reduction of engine sizes that comes with the replacement of more cylinder motors with fewer cylinder options while delivering the same amount of power.