Carrying five people in a vehicle can have a noticeable impact on fuel consumption, but the exact effect depends on several factors including the vehicle's size, engine type, and driving conditions.
On average, every additional 100 pounds (about 45 kg) of weight can reduce fuel efficiency by around 1%–2%. So, if five adults add a total of 300–400 kg (660–880 lbs), the fuel consumption could increase by approximately 5%–10%.
Smaller cars with less powerful engines are more affected by added weight than larger vehicles. Additionally, frequent stop-and-go driving or climbing hills will exaggerate the impact on fuel consumption.
In summary, a full car can noticeably increase fuel usage, especially over long distances or in city traffic, but the increase is generally manageable and depends on the vehicle's design and load capacity.
