In a four-stroke engine, a series of movements causes fuel to be converted into forward motion. All else being equal, the difference between a 4-cylinder and 6-cylinder engine is that the latter produces more power. This is due to the two extra cylinders that create additional piston thrust.
In a basic engine design, pistons travel down cylinder sleeves or chambers, allowing intake valves to open. Intake valves let fuel and air enter the cylinders, while rising pistons compress these gasses. Spark plugs ignite the compressed gas, causing explosions that drive the pistons back down. The next rise of the pistons coincides with exhaust valves opening to clear the chambers. The timing of the pistons is staggered so that one pair rises while another falls. Pistons are connected to rocker arms, which turn a crankshaft; then the driveshaft turns the wheels, thereby converting fuel into motion.
In a 4-cylinder engine, there are four pistons rising and falling in four chambers. A 6-cylinder engine features six pistons and produces a theoretical 50% more power than the same 4-cylinder engine. While a 4-cylinder engine might hesitate when you press on the gas, a 6-cylinder will tend to be more responsive, with greater get-up-and-go. The 4-cylinder engine is standard in smaller cars, as the relatively light weight of the vehicle makes it an economical choice with plenty of power for average motoring needs. Many models include a 6-cylinder engine upgrade option.
The 6-cylinder engine is standard on passenger cars, vans, small trucks and small to midsize sports utility vehicles (SUVs). Some of these models may also offer alternate engine designs as options. Standard trucks and larger SUVs commonly feature an 8-cylinder engine. These heavier vehicles are used for towing and carrying substantial weight.
Though more cylinders equal more power when comparing the same engine models, there are exceptions when comparing different engines. Improved engine designs over the years have resulted in substantial gains. This has made 4-cylinder engines more powerful than they were a decade ago, and 8-cylinder engines more fuel-efficient than they once were. In short, a 6-cylinder engine from 1993 that’s still running strong might nevertheless have less power than a recently designed 4-cylinder engine. In addition, a new 8-cylinder engine might get better gas mileage than the older 6-cylinder engine.
If deciding between a 4 and 6-cylinder engine on a new vehicle, there are a few considerations. The smaller engine will be less expensive and should get slightly better gas mileage. The disadvantage is a lack of power that might factor in more for commuters and travelers. For hilly or mountainous areas, the 6-cylinder engine would likely be a better choice. If interested in towing substantial weight, such as a powerboat or house trailer, consider an 8-cylinder motor.
Note that not all 4-cylinder engines are created equal. Differing technologies can make one engine feel gutless and another peppy. Differences also exist in larger engines of differing designs. The only way to tell if a particular engine will suit your needs is to give it a fair test drive.