2018 GMC Terrain: what breaks, and at what mileage

The failures owners actually file about

Owners have reported 47 named failure modes on the 2018 GMC Terrain, and the three most-reported carry 36% of everything filed.

Other brake problem leads with 48 reports, about 0.5 per 1,000 vehicles and with the middle half of reports between 17k to 70,000 miles.

Other engine problem follows with 37 reports, usually reported between 6k to 65,000 miles.

Other powertrain problem follows with 32 reports, usually reported between 3k to 20,000 miles.

By system, the reports fall mostly into brakes (76), engine (48) and transmission (38).

How bad it is when it goes

Across the named modes, 19 mention a crash, 2 a fire and 9 an injury. Those are the words owners used in their own complaints, and NHTSA does not verify them, but they are the closest thing in this data to a measure of what a failure actually did.

The average severity weight across every report on this year is 4.20, where a stalled engine or a failed airbag weighs many times more than a rattling trim panel, and a figure this high means the reports are dominated by failures with safety consequences rather than annoyances. The weighting is set out in full on the methodology page.

What the top failures cost to put right, as editorial estimates for an independent US shop rather than figures from NHTSA: other brake problem at $300–$1,800, other engine problem at $300–$4,000, other powertrain problem at $400–$4,500 and other electrical problem at $250–$2,000. Dealer labour, a seized bolt or a part that is no longer made can push any of these past the top of its range.

27% of the reports on this year sit in the engine, transmission, drivetrain or cooling systems — the four where a repair bill is usually four figures.

How often, against how many were built

Scaled by an estimate of how many of these cars exist, the 2018 GMC Terrain draws about 3.7 per 1,000 vehicles, which puts it in the 82nd percentile of complaint rates among 2018 vehicles we can rate.

That denominator is the weakest number on the page and it is fair to say so plainly. Rate per 1,000 uses a fleet-size estimate derived from recall paperwork for this exact model year. It is a lower bound.

The working figure is 88,503 vehicles. If the true number is twice that, every rate on this page is half what it says; the ranking against other 2018 vehicles, which is what the risk score uses, is far more robust than the rate itself.

Recalls on the 2018 model year

NHTSA has issued 5 recall campaigns covering the 2018 GMC Terrain, affecting an estimated 101,530 vehicles. A recall is a different kind of evidence from a complaint: it is the regulator and the manufacturer agreeing that something has to be fixed, and the fix is free for as long as the car exists.

The campaigns cover power train:automatic transmission, service brakes, hydraulic:foundation components:disc:caliper, fuel system, gasoline:delivery:fuel pump and air bags: air bag/restraint control module. Whether the work was actually done on the car in front of you is a question only the VIN can answer, and the manufacturer or NHTSA will answer it free.

One caution about reading these together: a recall usually raises the complaint count for the same part, because owners who read about it go and file. The mileages stay informative; the counts get noisy.

Where 2018 sits in the model line

Severe risk for a 2018 — 122nd riskiest of the 251 2018 vehicles we can rate. Because the ranking is against the same model year only, age cancels out of it.

Across the 17 model years of this car that carry enough reports to score, 2021 comes out best at 62 and 2019 worst at 80, with 2018 itself at 75.

If the model year is negotiable, 2021, 2016, 2015, 2022, 2014, 2025, 2017, 2026, 2023, 2013, 2012, 2010 and 2020 score lower than 2018 by a margin worth acting on. Same body, same engines, different luck — usually a supplier change or a mid-cycle fix, which the complaint data can show but never explain.

Within the 2018–2020 generation specifically, 2020 is the strongest year at 72 and 2019 the weakest at 80.

What the numbers say to check

The mileages below are where the first quarter of reports for each mode had already been filed, which makes them the point at which a fault is worth looking for rather than the point at which it happens: other electrical problem from about 2k, other powertrain problem from about 3k, other engine problem from about 6k and other brake problem from about 17k.

On a 2018 GMC Terrain with more miles than that on it, the useful question to put to a seller or a mechanic is whether other electrical problem has been dealt with, and if so with what parts and at whose expense. A car that has already had the repair is in a different position from one that has not.

Treat it as where to point the inspection, not as a prediction. A well-maintained example can sail past every mileage on this page, and a neglected one can fail well before the first of them.

What this page cannot tell you

328 owner reports; fleet size estimated from this year's own recall paperwork. Every count on this page is therefore a floor: it is the number of owners who went to the trouble of filing with a federal agency, which is a small and self-selected fraction of the owners who had the fault.

Of those 328 reports, 133 carried an odometer reading, so the mileages here describe 41% of the sample rather than all of it. Owners also round: readings pile up on multiples of ten thousand, which is why this site publishes "about 90,000 miles" and not "91,438".

The failure modes are assigned by software reading the owner's own words, which is accurate in bulk and wrong in individual cases. A mode with a handful of reports may contain a misfiled one.

And nothing here predicts what one car will do. These are other people's complaints, filed years apart, on cars maintained by strangers. Read the page as a map of where this model year has previously gone wrong, then have the specific car in front of you inspected.