Model Reports 4 min read Updated 18 Oct 2026

Hyundai i800 2018: reliability & common MOT faults

In 2025, 65 in every 100 first MOTs on a 2018 Hyundai i800 were passes. Most common reason for a fail: Individual sidelight or tail light (front).

Summary

The 2018 Hyundai i800 follows the pattern of the model years either side.

At a glance

How 1,087 first tests went in 2025.

Passed first time
65 in every 100
Did not pass first time
35 in every 100384 failed first-attempt tests
The typical car
7 yearsabout 74,512 miles
First tests counted
1,087

What failed most often

  1. Individual sidelight or tail light (front)29 in every 100 failed tests
  2. Headlight aim17 in every 100 failed tests

How we count this. Data: UK MOT open data, 2025. Only Class 4 cars on their first MOT of the year are counted. A car that fails and is fixed at the test station still counts as a fail in the first-attempt rate. These are raw results, not adjusted for age, mileage, or peer mix. The MOT does not test engine or gearbox internals.

Note:

These are patterns across 2018 Hyundai i800 vehicles in 2025, not a prediction that any one car will have them. Faults are grouped by part of the car. A wear pattern follows age and use more than the way the car was built. They come from MOT defect codes, not manufacturer bulletins, recalls or a diagnosis of any one car.

Lamps and electrical

Three faults and one wear pattern. The strongest is the individual sidelight or tail light (front): 10 times as often as on similar cars.

Figures below are measured across the 384 failed first attempts in 2025 that had a mileage recorded, which allows a like-for-like comparison.

We only list faults with at least 20 failures and a rate of about 2.0 times that of similar cars, which keeps one-off results out of the list.

Individual sidelight or tail light (front)

Failed on 110 first tests10 times as often as similar carsStrong evidence

What it means

A position lamp showing red light to the front or white light to the rear is Major. Rear lamps must show a steady red light, and front ones can show white, predominantly white with a blue tinge, or yellow if combined in a yellow headlamp. With a multiple light source, up to half not working is Minor and more than half is Major.

Number plate lights

Failed on 47 first tests4.9 times as often as similar carsLikely evidence

What it means

Registration plate lamps must light up the rear registration plate and operate at the same time as the position lamps. A missing or inoperative lamp is Major when the plate has only one lamp or all its lamps are not working, and Minor when the plate has several lamps or light sources and not all have failed. A lamp throwing direct white light to the rear is also Minor.

Headlight (front)

Failed on 45 first tests3.5 times as often as similar carsLikely evidence

What it means

On vehicles first used on or after a set date, a halogen headlamp unit converted to take HID or LED bulbs fails for light source and lamp not compatible, which is Major. A complete unit built with those light sources is not failed for that. The precise position of the lamps is not part of the inspection beyond a visual look to see that they sit at about the same height and distance from each side.

Headlight aim (front)

Failed on 65 first tests3.2 times as often as similar carsWear pattern

What it means

Beam aim too high, too low or off to either side is Major. Where a driver's beam aim control is fitted, the aim is tested without altering the setting, and rechecked at the highest setting only if it would fail for being too low. Masks or converter kits on right hand dip headlamps are acceptable.

Data: UK MOT open data, 2025. Compared with cars of the same age and mileage.

Noise, emissions and leaks

One fault: diesel engine warning light, 2.6 times as often as on similar cars.

Diesel engine warning light

Failed on 41 first tests2.6 times as often as similar carsPossible evidence

What it means

An engine malfunction indicator lamp that is illuminated to show a malfunction is graded Major on a diesel, but only on the diesels the test covers, which depends on the vehicle type and when it was first used. DVSA lists it under exhaust emissions for compression ignition engines, and the detail line for the row also names an inoperative lamp.

Data: UK MOT open data, 2025. Compared with cars of the same age and mileage.

Advisories

Other things testers noted as worn or close to failing, more often than on similar cars.

An advisory is a note from the tester about something that has not failed yet. It is an early warning, not a fail.

Non-component advisories

Noted on 25 first tests2.5 times as often as similar carsElevated evidence

Data: UK MOT open data, 2025. Counts cover advisories recorded on failed first tests only, compared with cars of the same age and mileage.

MOT pass rates

How first tests ended, and how the pass rates are counted.

Passed first time
65in every 100
Passed on the first test.
Fixed at the station
12in every 100
Failed, then fixed at the test station the same day.
Failed
23in every 100
Did not pass, and were not fixed at the test station.

First-attempt pass 64.7% of 1,087 first tests (2025): only cars that passed first time count. Official-style pass 77.2%: cars fixed at the test station also count as a pass. The 12 fixed and the 23 not fixed make the 35 in every 100 that did not pass first time.

Same model, other years

Passed first time in every 100, all tested in 2025.

YearPassed first timeFirst tests
201657 in every 100943
201763 in every 1001,222
2018 This car65 in every 1001,087
201971 in every 1001,658

Newer cars are younger, so look for a jump rather than the climb. A year earlier (2024), when these cars were a year younger, 62 in every 100 passed first time.

FAQs

Short answers about how to read this model-year guide.

The 2018 Hyundai i800 follows the pattern of the model years either side. Its main cause of failure was Individual sidelight or tail light (front), about 29 in every 100 failed tests. In 2025, 64.7% of 1,087 first MOTs on the 2018 Hyundai i800 passed first time (PRS: items fixed at the station the same day, counted as a fail). The official-style rate including PRS is 77.2%. Among 384 failed first-attempt MOT tests (test year 2025), Individual sidelight or tail light (front) appears more often than on similar cars (28.6% of those tests; 110 observed failures; about 10× more often than similar cars). There is no single reliability score here; this is a pre-purchase checklist built from DVSA open data, not a guarantee for any individual car.
Ranked by how often they were actually recorded, the items that most often failed a 2018 Hyundai i800 at the first attempt were Individual sidelight or tail light (front) (28.6%) and Headlight aim (16.9%), each as a share of the year's failed first attempts. That is what goes wrong most often on the car. The common faults table shows a different measure: faults that are unusual compared with similar cars.
Among failed first-attempt tests we highlight patterns that appear more often than on similar cars. Top example: Individual sidelight or tail light (front) (28.6% of those tests; 110 observed failures; about 10× more often than similar cars). These are statistical signals, not a diagnosis of any individual car.
Individual sidelight or tail light (front) shows up more often than on similar cars (28.6% of those tests; 110 observed failures; about 10× more often than similar cars). That does not prove a design fault. Age, mileage, and how the car was used still matter. Treat it as a pre-purchase checkpoint, not a manufacturer service bulletin.
Common MOT problem areas for the 2018 Hyundai i800 include Individual sidelight or tail light (front), Number plate lights, Headlight (front). These are the faults that stand out compared with similar cars, not a complete list of what can go wrong on any individual car.
Advisories flag issues noted at the test and are not a fail rate. We show advisory patterns that appear more often than on similar cars among failed first-attempt tests, separate from common failure rows. Use them as early-warning checks, not as a pass/fail score.
This page highlights MOT failure patterns for the 2018 Hyundai i800 (registration year) using UK DVSA open data for the selected test year. Patterns are compared with cars of a similar age and mileage. It is a buyer checklist from MOT defect statistics, not a full service history or manufacturer service-bulletin list.
No. MOT tests do not cover engine internals, gearboxes, or many electronic modules. Patterns here come from MOT defect statistics only and should not be read as engine or gearbox reliability scores.

About this data

How this page is built and what it can (and can't) say.

These figures come from UK MOT open data for this model year. We surface common failure patterns against similar cars, not a full reliability score, and not a pass/fail verdict on any individual vehicle.

2024 2025

What we include

UK Class 4 cars only. Normal MOT tests (not retests); first test per vehicle per calendar year; results pass, PRS, or fail.

Same-day repairs

PRS means the car failed items that were fixed at the test station and then passed the same day. We count PRS as a first-attempt fail in headline rates so same-day repairs do not hide problems.

How we compare

We compare this model year with other Class 4 cars of similar age and mileage in the same test year. This model family is left out of the peer group so the car is not measured against itself.

What this does not cover

  • MOTs do not cover engine internals, gearboxes, or many electronics; this is not a full reliability score.
  • Common faults come from MOT defect stats, not manufacturer TSBs or recalls.
  • Age and mileage matching reduces, but does not remove, differences in how cars were used and maintained.
  • If the data for a car is too thin to say anything useful, we say so rather than guess.

Contains public sector information licensed under the Open Government Licence v3.0.

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