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

Click For Summary
SUMMARY

The discussion centers on the impact of carrying extra weight, specifically golf clubs weighing approximately 10kg, in a Hyundai i30 (1.2-1.3 tonnes) on petrol costs. It concludes that the weight contributes negligibly to fuel consumption, with an estimated savings of only 0.2% in urban driving conditions and even less on highways. The primary factors affecting fuel efficiency include kinetic energy from acceleration, rolling resistance due to tire pressure, and wind resistance, with the latter two being largely unaffected by the additional weight of the clubs. Overall, the extra weight's effect on fuel costs is minimal compared to other factors such as driving habits and vehicle maintenance.

PREREQUISITES
  • Understanding of basic physics concepts such as kinetic energy and potential energy
  • Knowledge of vehicle dynamics including rolling resistance and wind resistance
  • Familiarity with fuel efficiency metrics and how they are calculated
  • Awareness of the impact of vehicle weight on performance and fuel consumption
NEXT STEPS
  • Research the effects of vehicle weight on fuel efficiency in various driving conditions
  • Learn about the principles of kinetic energy and how it relates to vehicle acceleration
  • Explore methods to optimize tire pressure for improved fuel economy
  • Investigate the role of regenerative braking systems in energy conservation
USEFUL FOR

This discussion is beneficial for automotive engineers, fuel economy analysts, and drivers interested in understanding the relationship between vehicle weight and fuel consumption.

mtallyn
Messages
1
Reaction score
0
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.
 
Engineering news on Phys.org
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 ). 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.
 
Last edited by a moderator:
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.
 

Similar threads

Undergrad Does Increasing Downforce Help a Car Stuck in a Hole More Than Pushing It?
  • · Replies 7 ·
Replies
7
Views
5K
Creating a timing correction factor for weight differences in karting
  • · Replies 4 ·
Replies
4
Views
11K
Car Power to Weight: How Much Extra HP Does Car A Need?
  • · Replies 6 ·
Replies
6
Views
3K
How Will My College Affect My Graduate School Acceptance?
  • · Replies 5 ·
Replies
5
Views
6K