Fuel Efficiency and Engine Size in Classic Cars

Isi
abril 27, 2026

Why this topic?

The mtcars dataset is used to create the interactive Plotly chart.
Fuel efficiency matters for both drivers and manufacturers.
Engine size and horsepower often trade off against miles per gallon.
An interactive chart makes those tradeoffs easy to explore.

What the data includes

This presentation uses 32 car models from the built-in mtcars dataset.

mpg: miles per gallon
disp: engine displacement
hp: horsepower
wt: vehicle weight
am: transmission type
cyl: number of cylinders

Interactive plot

This slide contains the Plotly code followed by the interactive chart. Hover over each point to inspect a car model, drag to zoom, or use the Plotly toolbar.

plot_ly(
  data = cars,
  x = ~disp,
  y = ~mpg,
  color = ~transmission,
  colors = c("#1b6ca8", "#d95f02"),
  size = ~hp,
  sizes = c(12, 36),
  text = ~paste(
    "<b>", model, "</b><br>",
    "Horsepower: ", hp, "<br>",
    "Weight: ", wt, " (1000 lbs)<br>",
    "Cylinders: ", cylinders
  ),
  hoverinfo = "text",
  type = "scatter",
  mode = "markers",
  width = 900,
  height = 430
) %>%
  layout(
    title = "Fuel efficiency falls as engine displacement grows",
    xaxis = list(title = "Displacement"),
    yaxis = list(title = "Miles per gallon"),
    legend = list(title = list(text = "Transmission"))
  ) %>%
  config(
    displayModeBar = TRUE,
    displaylogo = TRUE,
    modeBarButtonsToRemove = c(
      "toImage",
      "zoom2d",
      "pan2d",
      "select2d",
      "lasso2d",
      "zoomIn2d",
      "zoomOut2d",
      "autoScale2d",
      "resetScale2d",
      "hoverClosestCartesian",
      "toggleSpikelines"
    )
  )

Main takeaway

Smaller engines tend to deliver better fuel economy.
Manual cars often appear among the more efficient models.
High-horsepower cars are concentrated in the low-MPG region.