Why Does Engine Size Affect Car Insurance Costs? When you are searching for a car insurance quote one of the single biggest factors in determining the cost is the size of the engine of the car. But why does this make such a huge impact on the cost? A lot of people ask questions such as: does car insurance cost more by engine size? Well read on to find out why engine size affects insurance. What Is Engine Size? The size of a car engine is worked out by multiplying the volume of one cylinder of the car engine by the amount of cylinders it contains. For example if we take a typical 2.0 litre engine it might consist of: 500cc per cylinder x 4 cylinders = 2.0L. In general terms a larger engine will consume more fuel than a smaller engine over the same distance traveled. A diesel engine will produce less power than its petrol equivalent therefor using less fuel. The Theory The theory behind engine size and insurance cost comes down to a simple concept that the insurance companies believe that the people who will be buying vehicles with a larger engine size will be looking to drive their cars faster and more dangerously and therefor resulting in more accidents and claims. They believe that the larger engine size will appeal to the "boy racer" stereotype who are more likely to make claims.