How does a car's loads affect it's fuel consumption?

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Discussion Overview

The discussion centers around how various electrical loads in a car, such as LED lights, MP3 players, and air conditioning systems, affect fuel consumption. Participants explore the relationship between electrical power consumption and fuel usage, considering both theoretical and practical implications.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants inquire about the specific electrical loads in a car and their impact on fuel consumption over extended periods.
  • One participant questions the relationship between the air conditioning system's power consumption and fuel efficiency, suggesting that running the AC might improve gas mileage under certain conditions.
  • Another participant argues that running the AC does not improve gas mileage and claims that driving with windows open is more fuel-efficient.
  • A participant describes an experiment demonstrating how turning on lights affects engine RPM and fuel consumption, suggesting that electrical loads create mechanical resistance that impacts fuel usage.
  • Another participant shares an anecdote about driving an older car with a dynamo, noting that turning on electrical accessories significantly reduces the car's speed, implying a direct relationship between electrical load and fuel consumption.
  • One participant humorously suggests that fuel consumption may depend on external factors, such as terrain and passenger weight.

Areas of Agreement / Disagreement

Participants express differing views on the impact of air conditioning on fuel efficiency, with some suggesting it may improve mileage while others contest this claim. The discussion remains unresolved regarding the overall effects of various electrical loads on fuel consumption.

Contextual Notes

Participants do not provide a clear consensus on the definitions of terms like "LED system" or the specific mechanisms by which electrical loads affect fuel consumption. There are also varying assumptions about the conditions under which these effects may be observed.

Aicy
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Hi, so I was wondering about how the car's LED, MP3/IPOD, AC systems consumes up electrical power and then to fuel?

Let's say that the loads are running for 5-7 hours. Thanks for the replies/ideas!
 
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Aicy said:
Hi, so I was wondering about how the car's LED, MP3/IPOD, AC systems consumes up electrical power and then to fuel?

Let's say that the loads are running for 5-7 hours. Thanks for the replies/ideas!

Welcome to the PF.

What is a car's LED system?

And a car's air conditioning system (AC) power consumption is very different from any MP3/radio power consumption. Why may running the AC actually improve gas mileage?

Do you know the conversion between horsepower and watts? :smile:
 
Also, what is the context of your question? Are you wanting to have some ammunition to make your kids turn off their MP3 players on long trips? :biggrin:
 
Running the cars AC system doesn't improve gas mileage. Failing to drive with the windows open improves gas mileage.
 
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Likes   Reactions: Jeff Rosenbury and berkeman
Aicy said:
Hi, so I was wondering about how the car's LED, MP3/IPOD, AC systems consumes up electrical power and then to fuel?

Let's say that the loads are running for 5-7 hours. Thanks for the replies/ideas!
Had a friend that did not believe that lights influence consumption. A simple demo.
Engine on. Lights off. Car in neutral. Look at the rpm meter. Turn on lights.
The rpm will fall slightly from the drop in electrical resistance which puts more mechanical resistance on the "alternator" and as it is connected to the engine rpms get affected. And they rise back from more fuel given to the engine by the "regulator" (no idea of the terminology in EN).
 
Any energy taken from the fuel that is not used to drive the wheels will increase fuel consumption.
Anybody ever driven an old car that has an dynamo rather than alternator? Every time you switch on something, the car gets slower...try it in the winter with the lights, heater, wipers on, any attempt to put on the radio and the car almost stops!
 
when I first read this question I thought "It depends on the terrain and how many fat ladies".
 

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