Turning Repair History Into a Reliability Score

Reliability is usually discussed as a brand-level abstraction, but the vehicle sitting in your driveway has its own history, and that history predicts its future far better than any badge does. This calculator scores six dimensions on a 0-100 scale and combines them by weight: repair frequency at 30%, repair cost at 20%, failure severity at 20%, availability at 12%, maintenance compliance at 10%, and open recalls or warning lights at 8%. Frequency dominates because a pattern of unscheduled repairs is the strongest single predictor of more repairs to come.

Why Severity Is Scored Separately From Cost

Two vehicles can spend identical amounts in a year and be in completely different condition. One replaced four inexpensive sensors; the other rebuilt a transmission. The dollar totals match but the outlooks do not, because major powertrain failures correlate strongly with further major failures while small electrical faults largely do not. That is why a single engine or transmission event drops the severity dimension to 15 out of 100 regardless of the invoice, while a string of minor wear items leaves it near 78.

Measuring Cost Against Value, Not in Dollars

Absolute repair spend is nearly useless for comparison, because $800 is trivial on a $45,000 vehicle and alarming on a $6,000 one. Expressing repairs as a percentage of current value converts the figure into a decision. Below roughly 15% the vehicle remains clearly economical to keep. Between 15% and 30%, each major failure deserves individual reassessment. Above 30% per year, replacement is usually cheaper once you account for downtime and the risk of the next failure, even allowing for the depreciation a newer vehicle brings.

Using the Score to Decide What Comes Next

The score's practical value shows up in three decisions. First, whether to keep the vehicle: Professional Mode projects repair costs forward at a 12% annual escalation and states an explicit keep-or-replace verdict. Second, whether an extended warranty makes sense: above a score of 85 the premium is unlikely to be recovered and a self-funded repair reserve serves better, while below 70 a warranty can genuinely pay for itself. Third, what to fix first: the dimension chart shows exactly which factor is dragging the total down, and maintenance compliance and open recalls are usually the cheapest points to recover, since recall work is performed free of charge at any franchised dealer.