How the overall GPA is weighted

The headline GPA on every card is not an average of the ten subjects. It is a weighted blend of seven of them, and three are graded on their own and left out. The weights are published in the framework and reproduced here, with the reasoning — because a weighting is the most opinionated thing in any scoring system, and it should be the easiest thing to find.

The formula

Safety and Reliability carry the most, a fifth each. Performance and Space & Comfort carry 15% each. Technology, Driving Experience and Value round it out at a tenth apiece. The last column is the practical reading: because the GPA is linear in the score (see How the GPA scale works), a one-point improvement in a subject scoring moves the overall GPA by that subject’s weight times 0.0698. Ten points of Safety is worth 0.14 of GPA; ten points of Technology, 0.07.

Why Safety and Reliability lead

They are the two subjects that decide whether a car is a good decision rather than a pleasant one. A vehicle that is agreeable to drive and well equipped but unreliable is a vehicle you regret; one that is dull but safe and dependable is one you keep. The weighting encodes that, and it is why a car with a strong Reliability grade can carry a respectable GPA on a mediocre showing elsewhere — and why the reverse is hard. The subject medians make the point: on the latest scorecards, Reliability sits at 66.9 points (C+) and Safety at 72.9 (B-), against 72.5 for Technology and 69.3 for Driving Experience. The two heaviest subjects are also two of the harder ones to score well in.

The three that are left out

Efficiency & Range, Cost of Ownership, Use-Case Fit do not feed the overall GPA. Each is graded and ranked in full — it has a subject grade on every card, a plaque on the honor roll, a column on the compare page — but it is not blended into the headline. The reasons differ.

Efficiency & Range

Efficiency is graded within powertrain class, because MPG and MPGe are not the same measurement; a gas car’s 70 and an EV’s 70 each mean “good for its class” and blending them into one number would compare band placements rather than cars. It is also the subject where the framework’s bands are known to sit hard — the median car currently scores 49.5 points, a D — and folding that into every GPA would drag the whole fleet down for a reason that has nothing to do with how good the vehicles are. So it stands alone, labelled with its class wherever it is printed. Efficiency is graded within powertrain class is the full account.

Cost of Ownership

Ownership cost is dominated by price and depreciation, and price is the one thing a buyer has already decided before reading a review. Blending it into the GPA would make every expensive car look worse at being a car, which is a different claim from being worse value. It also has the same calibration problem as efficiency in a more acute form: the median vehicle scores 42.9 points, a F, and the reason is the framework rather than the fleet. Until that is retuned, keeping it out of the headline is the honest choice.

Use-Case Fit

Use-case fit is four separate scores — family, commuter, work, adventure — and a vehicle is supposed to be good at some and not others. A minivan that scores poorly on work and towing is not a worse minivan. Averaging the four would reward vehicles for being unspecialized, so the four are kept apart and drive the decider and the fit card on each car page instead.

What a weighting cannot do

Any single number loses information, and this one loses it in a known direction: toward the middle. A car with an A in Safety and a D in Reliability blends to a C+; so does a car with a C+ in both. The headline says they are equally good decisions, which is defensible, but it hides the fact that they are very different cars. That is why MotorGPA never shows the GPA without the subject grades beside it, and why the report-card metaphor was chosen in the first place: a transcript is more useful than an average.