BMW 8 Series used buyer’s guide (G15): best year, engine and the checks before deposit

A BMW 8 Series used buy is one of the great grand-touring bargains of 2026: a car that cost north of £80,000 new now starts under £25,000, and the right one drives like nothing else at the money. The catch is that the spread between a good car and a money-pit is wide. Our pick is a 2020 onwards 840i M Sport with full BMW history, and our advice is to walk away from any example with a vague service record or a soft-top you cannot hear cycle smoothly.

Why the 8 Series is the used GT bargain of 2026

BMW built this car (G15 coupe, G14 convertible, G16 Gran Coupe) from 2018 to 2024 as a flagship grand tourer to sit above the 6 Series, and it launched at roughly £76,000 to £100,000-plus depending on engine and trim. Depreciation has been brutal, which is exactly why it works as a used buy. A 2021 840i M Sport coupe with around 35,000 miles now sits near £26,250, and a 2018 840d coupe with 70,000 miles around £26,750 on Auto Trader listings checked in June 2026. That is luxury-saloon money for a hand-built-feeling two-door. If you are cross-shopping other premium coupes, the same depreciation logic drives our Porsche 911 used buyer’s guide, though the 911 holds value far harder than the BMW does.

The engine line-up: 840i, 840d, M850i and the M8

Four engines matter here, and they are not the same family. The 840i runs the 3.0-litre B58 turbocharged straight-six (340PS), the sweet spot for most buyers: smooth, strong and cheaper to insure and fuel than the V8s. The 840d uses the 3.0-litre B57 turbo-diesel six with mild-hybrid assistance (also 340PS), a genuine 40-plus mpg cruiser but tied into the EGR recall story below. The M850i xDrive carries the 4.4-litre N63 twin-turbo V8 (530PS), and the full M8 and M8 Competition (separate F92, F91 and F93 model codes) use the harder-edged 4.4-litre S63 V8 at 600PS to 625PS. Our view: the B58 840i is the connoisseur’s value pick, the M850i is the one to covet, and the M8 is a specialist purchase only if you understand its running costs.

Coupe vs Gran Coupe vs convertible: which body suits you

The G15 coupe is the purist’s choice and the cleanest shape, but rear seats are token. The G16 Gran Coupe stretches the wheelbase into a genuine four-door that doubles as a sporting alternative to a 7 Series, and it tends to be the value buy of the three because supply is higher. The G14 convertible adds drama and a fabric roof that becomes a maintenance item (see below). For most UK buyers we would take the Gran Coupe for usability or the coupe for looks, and treat the convertible as a heart-over-head call. If a four-door BMW flagship is really what you want, weigh it against our BMW 7 Series G11 used guide before you commit.

Common faults to check before you buy a BMW 8 Series used

This is the section that saves you money. The headline reliability is genuinely strong, but owners flag a consistent cluster. Electronics top the list: iDrive freezes, sat-nav glitches and the odd dead screen are the single most-reported gripe in our forum sweep, so spend ten minutes cold-booting every system on a test drive. On diesel 840d cars, confirm the EGR cooler recall work has been done (more below). The integral active steering and adaptive suspension are owner-reported worry points, expensive if they fail out of warranty, so listen for clonks over speed bumps and check the steering self-centres cleanly. On the convertible, cycle the soft-top fully up and down twice; a hesitant or noisy mechanism is a deposit-killer. None of this is unique drama for a six-figure-when-new BMW, but the repair bills are firmly premium.

The diesel EGR recall and other safety actions

BMW’s long-running EGR cooler recall, which targets a glycol coolant leak that can pose a fire risk on diesel engines, was extended in November 2022 to cover G1x 7 and 8 Series cars, so any 840d on your shortlist must have the work logged. Use the free gov.uk vehicle recall checker with the registration before you pay a deposit. Wider 8 Series safety actions reported across the range have included starter-motor overheating, airbag and reversing-camera items, so a clean recall record verified against DVSA data is non-negotiable. For petrol 840i and M850i cars the recall exposure is lower, which is another quiet point in the petrol six’s favour.

Running costs: tyres, servicing, tax and depreciation

Budget honestly. The V8 cars drink fuel and chew premium tyres; staggered rubber on an M850i or M8 can run into four figures a set. Servicing at a BMW main dealer is not cheap, though a fixed-price service plan or a trusted independent softens it. Every 8 Series fell into the higher first-year and premium-supplement VED brackets when new, so check the current standard rate applies on your chosen car. The good news is depreciation has already done its worst: a car that shed most of its value in its first three years is far more stable now, so a well-bought 2020-2021 840i should hold up better than the original owner’s did. If you are funding the purchase, the trade-offs in our PCP vs HP guide for a premium coupe apply almost directly to a £25,000 to £40,000 8 Series.

Best year and engine: our pick by budget

Under £30,000, target a 2020-2021 840i M Sport coupe or Gran Coupe with full BMW service history; it gives you the strong B58 six, the post-launch software maturity and the lowest running costs of the range. In the £35,000 to £50,000 band, the M850i xDrive is the car to want, with the N63 V8’s effortless pace and all-weather traction, ideally still inside BMW Approved Used cover. The 840d makes sense only as a high-mileage motorway tool, and only with the EGR recall confirmed. We would step past the very earliest 2018-2019 cars where you can, simply because the later examples ironed out early electronic niggles. Across the board, history and a clean recall record matter more than colour or wheel size.

That reliability standing is more than folklore. In the What Car Reliability Survey for the used 8 Series, the car returned 96.9% and placed fourth of 15 in its class, evidence that the cluster of faults owners report tends to be irritating rather than catastrophic.

8 Series vs a used S-Class coupe or Continental GT

The BMW’s natural rivals at this money are the Mercedes S-Class Coupe and a used Bentley Continental GT. The BMW is the keener driver’s car and far the cheapest to run of the three. A Continental GT delivers more presence and a W12 soundtrack but lands you with Bentley servicing and tyre bills that dwarf the BMW’s. The S-Class Coupe is the plush cruiser; if outright luxury is the goal, the related saloon in our Mercedes S-Class W222 used guide shows where that money goes. Our take: the 8 Series wins on driver appeal and cost per mile, the S-Class on ride comfort, and the Bentley only if badge presence trumps your maintenance budget.

Insurance and warranty: protect a premium coupe

Two paperwork jobs make or break ownership. First, cover: an 8 Series sits in high insurance groups, and the V8 cars sit higher again, so quote before you buy, not after. The trade-offs we set out in our BMW M and Audi RS insurance guide apply directly to an M850i or M8. Second, warranty: if the car is still within BMW Approved Used, that 12-month cover is worth real money on a car with pricey electronics. Where it has lapsed, weigh a quality aftermarket policy, and our approved-used warranty comparison shows what manufacturer schemes actually include versus the gaps you fill yourself.

Pre-deposit checklist: what to verify before you pay

Run these before any money changes hands. Check the full MOT history on the gov.uk MOT checker for advisories on tyres, brakes and suspension. Run the registration through the gov.uk recall checker and, on a diesel, confirm the EGR work is logged. Demand full BMW or specialist service history with stamps, not a printout. Cold-start every electronic system and cycle a convertible’s roof twice. Inspect tyres for matched, in-date premium rubber. Finally, get an independent inspection on any M850i or M8; the saving on one avoided V8 or suspension fault pays for it many times over.

Our take

Buying a BMW 8 Series used in 2026 is one of the smartest ways to get genuine grand-touring magic for premium-saloon money, provided you buy with your head. Our clear pick is a 2020 onwards 840i M Sport with complete BMW history: the B58 six is the connoisseur’s engine, running costs are the most sensible in the range, and the worst of the depreciation is already behind it. Step up to an M850i if you want the V8 drama and can stomach the tyre and fuel bills, and treat the M8 as a specialist toy rather than value transport. Walk away from any car with patchy history, an unconfirmed diesel recall, a tired soft-top or live electronic faults. Get the paperwork right and an inspection done, and the 8 Series rewards you every time you drive it. Get it wrong and the repair bills bite hard.