# How much does car boot/trunk weight increase petrol costs?

• mtallyn
In summary, the conversation discusses the potential cost and impact of leaving golf clubs in a car. It is estimated that the weight of the clubs may result in a 0.2% decrease in gas mileage and contribute to increased kinetic energy and rolling resistance. However, the overall effect on gas mileage may be minimal and other factors such as wind resistance and engine friction may have a larger impact.

#### mtallyn

I often leave my golf clubs in the car rather than bothering to take them out I just wondered how much extra this is costing me. I have an Hyundai i30 ps109, ~1.2-1.3 tonnes and the clubs are about 10kg but more than happy for average car specs/approximations to be used. Can anyone do the maths? I'd be really curious to know.

You'd be lucky to get about 0.2% saving around town, less than half that on the motorway/autoroute/bahn/strada/pista etc. (www.drivealuminum.org/research-resources/.../2008-Ricardo-Study.pdf [Broken]). Note that this is probably less than the weight of a quarter of a tank of fuel, so you would save more by only filling up to half way when refuelling.

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There are (at least) two separate parts to this.

First, every time you accelerate, the extra mass acquires kinetic energy (##mv^2/2##), and unless you car has a regenerative braking system, your brakes convert that energy into heat when you slow down.

Second, unless you adjust the tire pressures, extra weight increases the rolling resistance of the tires.

An extra 10kg weight probably won't make much difference, though.

Thirdly; If you play golf once per week, but drive to work every day over a 1000 foot ridge. Then the mass must be raised 1000 ft, twice each day. PE = m * g * h

There are three factors (maybe more) that affect gas mileage.

The first is wind resistance. This could be the biggest factor but the golf clubs won't affect it.

The second is the friction generated by the engine, air conditioning, bearings etc. The clubs won't appreciably affect this either.

The third is as has been mentioned already, the increased energy expended to accelerate the extra mass and the increased rolling resistance. This factor is probably proportional to the mass of the car, thus the ratio of the mass of the car without the clubs to the mass with the clubs would be the multiplier for this third factor. What is left is to determine what proportion of the total is the third factor.

## 1. How does the weight of my car's boot/trunk affect petrol costs?

The weight of your car's boot/trunk can have a significant impact on the amount of petrol your car uses. The heavier your car is, the more energy is required to move it, resulting in increased petrol consumption.

## 2. Does the weight of items in my car's boot/trunk affect petrol costs?

Yes, the weight of items in your car's boot/trunk can also contribute to increased petrol costs. The more weight your car is carrying, the more energy is needed to move it, thereby using up more petrol.

## 3. How much does the weight of my car's boot/trunk increase petrol costs?

The exact amount may vary depending on factors such as the weight of the car and the distance traveled, but on average, every 100 pounds of extra weight can decrease fuel economy by about 1-2%. This means that a heavier car boot/trunk can increase petrol costs by a few cents per gallon.

## 4. Can removing unnecessary items from my car's boot/trunk save on petrol costs?

Yes, removing unnecessary items from your car's boot/trunk can help save on petrol costs. By reducing the weight of your car, you can improve its fuel efficiency and save money on petrol.

## 5. Are there any other factors besides weight that can affect petrol costs?

Yes, there are several other factors that can affect petrol costs, such as driving habits, road conditions, and vehicle maintenance. For example, aggressive driving and frequent stops and starts can decrease fuel efficiency, resulting in higher petrol costs. Keeping your car well-maintained, with properly inflated tires and regular oil changes, can also help improve fuel efficiency and save on petrol costs.