Across 392 vehicles, average fuel efficiency is 24.4 MPG with a range of 29.8 MPG, reflecting dramatic variation driven primarily by engine configuration. Weight and MPG are correlated at r = -0.95, confirming weight as the dominant single predictor. Together weight, horsepower, displacement, and cylinders explain 92% of MPG variance (R² = 0.92); weight carries the largest standardized regression coefficient.

The average vehicle achieves 24.4 MPG (SD = 7.0) with a mean weight of 2789 lbs and 124 horsepower. The wide standard deviation in MPG indicates substantial fleet heterogeneity, driven by the mix of 4-, 6-, and 8-cylinder vehicles spanning over a decade of model years.

Weight correlates with MPG at r = -0.95 — the strongest single-attribute relationship in the dataset. Displacement and horsepower are nearly as strongly correlated with MPG (and with each other), suggesting significant multicollinearity: knowing weight already tells you much of what displacement and horsepower would add.

Each point in the scatter represents one vehicle (392 total). The strong downward trend (r = -0.95) confirms that heavier cars consistently achieve lower MPG. Clear clusters appear by cylinder count (5 groups), with 8-cylinder vehicles occupying the high-weight / low-MPG corner and 4-cylinder cars clustering in the light-weight / high-MPG region.

4-cylinder engines average 29.4 MPG versus 16.4 MPG for 8-cylinder engines — a gap of 13.0 MPG. The box plots reveal not only different medians but also different spread: 8-cylinder vehicles cluster tightly in the low-efficiency range, while 4-cylinder cars show more variation, reflecting the broad range of compact and economy models.

Average fleet MPG rose from 24.2 (model year 70) to 24.7 (model year 82), a gain of 0.5 MPG over the period. The most efficient model year was 79. The steepest improvements coincide with regulatory pressure and oil-price shocks in the mid-to-late 1970s, when automakers accelerated the shift to lighter, more fuel-efficient designs.

Standardized regression coefficients show weight as the single largest contributor to MPG prediction (beta = 0.800), meaning a one-SD shift in weight is associated with a 0.800-SD change in MPG, holding other variables constant. The four-predictor model explains 92% of MPG variance (R² = 0.920).

The top 20 most fuel-efficient vehicles average 36.2 MPG at a mean weight of 1700 lbs. 80% are 4-cylinder models, confirming that cylinder count is the primary structural differentiator of high-efficiency vehicles. The most efficient car in the dataset is the oldsmobile rabbit at 38.8 MPG.