What Makes a Car Fuel-Efficient?

An Interactive Data Story Using R and Plotly

The Question

Can horsepower help explain a car’s fuel efficiency?

• Fuel efficiency is measured in miles per gallon (MPG).
• Horsepower measures engine power.
• Vehicle weight may also influence fuel consumption.

Our goal is to explore the relationship between engine power, vehicle weight, and fuel efficiency using an interactive visualization.

Created: October 24, 2026

Meet the Dataset

The mtcars dataset contains measurements for 32 car models from a 1974 Motor Trend magazine dataset.

Variables used

• mpg: Miles per gallon
• hp: Gross horsepower
• wt: Weight in 1,000 pounds
• cyl: Number of cylinders

This dataset allows us to explore patterns between vehicle characteristics and fuel efficiency.

Explore the Relationship

Hover over the points to explore individual cars. Zoom in, pan across the graph, and compare the different efficiency groups.

Bubble size represents vehicle weight. Colours distinguish cars above and below the dataset’s median MPG.

What Do the Numbers Tell Us?

• Horsepower and MPG correlation: -0.78

• Weight and MPG correlation: -0.87

• Median fuel efficiency: 19.2 MPG

How to interpret these results

• A negative correlation indicates that higher values of one variable tend to be associated with lower values of the other.
• Correlation does not establish cause and effect.
• The results describe this dataset, not every car on the road.

Why Use an Interactive Plot?

An interactive visualization helps readers investigate the data themselves.

• Hover: View individual car measurements.
• Zoom: Examine clusters of data points.
• Pan: Navigate across the graph.
• Legend: Compare higher- and lower-MPG groups.
• Bubble size: Observe differences in vehicle weight.

These features make the visualization more informative than a static image.

Key Findings

1. Horsepower and fuel efficiency

The correlation indicates the direction and strength of the relationship between horsepower and MPG in this dataset.

2. Vehicle weight matters too

The weight–MPG correlation helps us examine whether heavier vehicles tend to have lower fuel efficiency.

3. Relationships are not explanations

Engine design, transmission, cylinders, and other characteristics may also contribute to differences in fuel consumption.

Conclusion

This interactive exploration demonstrates how R and Plotly can be used to investigate relationships in a real dataset.

The analysis allows us to:

• Examine horsepower and fuel efficiency.
• Compare vehicle weights and MPG.
• Inspect individual car measurements.
• Calculate and interpret correlations.

Main takeaway: Data visualization helps identify patterns, but further analysis is needed before drawing causal conclusions.

Methodology and References

Methodology

• Dataset: mtcars, included with R.
• Software: R and RStudio.
• Visualization: Plotly for R.
• Analysis: Descriptive statistics and Pearson correlation.
• Limitation: Small, historical dataset that may not represent modern vehicles.

References

1. R Core Team. R: A Language and Environment for Statistical Computing.
   https://www.r-project.org/

2. R Documentation. Motor Trend Car Road Tests (mtcars).
   https://stat.ethz.ch/R-manual/R-devel/library/datasets/html/mtcars.html

3. Plotly. Plotly for R Documentation.
   https://plotly.com/r/

Thank You!

Questions?

An interactive data story created using R Markdown and Plotly.

October 24, 2026