BMW M340i (G20) Review: 46/70

The Buyer's Guide

We scored the car as a 2020-on BMW M340i sedan with the B58 3.0-litre turbo six, the eight-speed automatic and rear-wheel drive, and it landed at 46 out of 70, with a verdict of Buy a 2021+, or a recalled 2020.

This car is for someone who wants the Supra 3.0's engine with a back seat and a trunk, and who accepts paying full price for it and losing a steady slice of that price every year.

All money figures use a fixed set of assumptions so they can be compared to other cars we cover: 12,000 miles a year, insurance for a 40-year-old with a clean record on full coverage, and premium fuel at $4.00 a gallon. Prices are Kelley Blue Book private-party in Good condition, on the 2022 model year. We scored the rear-drive car. The xDrive version is about 3,968 lb against the rear-drive car's 3,849 lb, and one of the recalls below reaches only the xDrive. This is not the F30-generation 340i, which used an earlier, lower-output tune of the same engine family.

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The Deal

~ our estimate, not a measured or quoted figure · [S] one credible source, uncorroborated · * there is a caveat, and the note under the table explains it. Why we mark figures

Kelley Blue Book values a 2022 M340i sedan with rear-wheel drive at $36,360 in Good condition private party. KBB does not say what mileage that assumes. Its condition range for the same car runs from about $34,260 to $37,860.

Asking prices are well above that. On September 26, 2026 we pulled every 2020-on M340i listed on Cars.com and kept the rear-drive ones: 13 cars, from $30,501 to $58,287, with a median of $48,587. That is 1.34 times book. It is a live snapshot, so it will have moved by the time you read this.

The same pull turned up something we did not expect. Of the 23 listings, 13 were rear-drive and 10 were xDrive. We had estimated the market at roughly 70-80% xDrive, from general reporting on how BMW's six-cylinder cars sell, and this sample points the other way. It is one sample of 23 cars, not a sales figure, so we are not replacing one estimate with another. What it does tell you is that a rear-drive car is not hard to find.

Two figures decide the Deal score. What you lose: KBB puts a 2022 at about $52,676 in 2023 and $36,900 now, 29% in three years. Compounded, that is about 11.2% a year, or about $4,068 a year on the $36,360 buy-in. What you get: $36,360 buys 10.08 lb per hp, against $17,868 for what that power-to-weight usually costs across our Board, so you are paying 2.03 times the going rate. That is $95.2 per horsepower on book and $127.2 on the asking median. Both halves count against it, and that is why the Deal is a 2.

For a named comparison, the Supra 3.0 is $42,000 on book for the same 382 hp, with two seats.

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The Drive

382 horsepower at 5,800 rpm and 369 lb-ft from 1,850 to 5,000 rpm, in 3,849 lb. That is 10.08 lb per hp. The output has not changed from 2020 through 2025, including the 2022 facelift, which added a 48V mild-hybrid system that BMW describes as helping low-end response rather than raising peak power.

We do not have a 0-60 time for it. The instrumented tests of this car we found all come from outlets outside the sources we use, so they are not here. BMW's own claim for the rear-drive car is 4.4 to 4.5 seconds, and that is a manufacturer figure, not a test.

The gearbox is ZF's eight-speed automatic, and that is the whole list: BMW never offered the M340i with a manual. Power goes to a limited-slip rear differential, an electronically controlled M Sport unit, which is standard.

The engine is the B58, the same family and essentially the same output as the Supra 3.0's 382 hp and 368 lb-ft, and we rate its powertrain character a 5 on both cars. The steering is electrically assisted, and we rate it a 3, precise but numb, the same read as the F30-generation cars before it. The Supra 3.0 carries the same engine in 3,400 lb (8.9 lb per hp) and ran 3.9s to 60, and its Drive is a 9. The M340i is the heavier car with the duller wheel, and lands on 8.

Cornering is not in this score; that is The Limit.

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The Upkeep

About $6,025 a year: $1,846 in fuel, $2,808 in insurance, $571 in tires and about $800 in service.

The rear-drive car is rated 26 mpg combined, 23 city and 32 highway, on fueleconomy.gov's own listing for it. BMW specifies 91-octane premium. Running 93 lets the engine use more ignition timing, but it is not a stated requirement, and we costed it on 91.

Insurance is the biggest line, and this time it is a quote for the car rather than the nameplate. MoneyGeek breaks the 3 Series out by trim, and its "M340i Sedan 4d" row comes to $234 a month on full coverage, $2,808 a year. A plain "M340i" row on the same table reads a little lower, at $2,736.

The tires are staggered, 225/40R19 at the front and 255/35R19 at the rear, so the fronts and rears cannot be swapped to even out wear. Tires are on our Board tire rule, the same for every sedan we cover: a Continental ExtremeContact Sport 02 in the factory sizes, priced at SimpleTire, one set every 24,000 miles. That is $281.99 a front and $288.99 a rear, a $1,141.96 set, or $571 a year. Service at about $800 a year is our estimate, at the same level we use for the Supra 3.0's B58. Against the Supra 3.0's $5,346 a year, the M340i costs more to keep, mostly on insurance.

What year one costs, by condition

These are our estimate for a car at 60,000 to 90,000 miles, in parts and independent labour. The maintained end is fluids, brakes and a set of tires. A cracked coolant tank or a failed electric water pump, $300 to $1,500 between them, is what pushes the typical column up. The top of the neglected column is the 2020 oil pump below. A 2021-on car does not carry that line at all, which is why the spread is so wide: on a car this young, one model-year problem decides it rather than years of general wear.

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The Risk

The repair to know about is the oil pump on 2020 model-year cars. Its pressure-relief ring is plastic, and it can fail; owners report it from roughly 30,000 to 60,000 miles, with no fixed point. BMW moved to an all-metal pump for 2021.

What that repair costs is disputed, and we are giving you both figures rather than picking one. One figure puts it at $6,000 to $8,000, because the front subframe has to come off to reach the oil pan. The page we first had for that number turned out to be a general guide to the same engine in BMW's X5, X6 and X7, not the M340i, and we dropped it. A repair-cost estimator we found in passing suggests about $2,100 to $3,000 for a straightforward pump replacement on this car. We could not confirm either against an M340i shop quote. If you are looking at a 2020, get your own quote before you buy.

Recall 21V-598 covers the same cars: 2020 M340i and M340i xDrive, about 10,877 in the US, built from February 2019 to July 2020. Engine software can command the combined oil and vacuum pump in a way that damages it, which can reduce or remove vacuum brake assist; full mechanical braking stays. BMW dealers update the software free and replace the pump free if it is already damaged. Whether that recall and the plastic-ring failure are the same root cause is not confirmed. Owners report that BMW's 2021 change was both the metal pump and a software update. Either way, a 2020 with 21V-598 done is a much safer 2020, and you can check that by VIN. Warning signs owners report are oil pressure past 90 psi under load and an oil level the car will not read, but nothing confirms a pump that has not failed yet.

Two more recalls reach this rear-drive car, both free. 23V584000 updates software that may fail to sound the seat-belt chime on 2019 to 2022 cars. 26V056000 replaces a starter that can overheat and catch fire, across 87,394 3 Series from 2021 to 2024. A third, 23V-211, replaces poorly welded front seat frames, but it covers the M340i xDrive and not the rear-drive car.

The rest of the list is the B58's usual: a plastic coolant expansion tank that cracks with age at $300 to $600, an electric water pump at $800 to $1,500, and valve cover and oil filter housing gaskets that seep, at $350 to $700 and $200 to $500. The timing-chain trouble of BMW's older N54 and N55 sixes does not carry over in the same way; owner consensus has B58 tensioner failure as rare and usually well past 150,000 miles.

NHTSA holds 51 complaints for the 2020 M340i, 11 for the 2021 and 6 for the 2022, and 15 of the 2020's are filed under the engine. Newer cars have had less time to collect complaints, so read the fall loosely.

The Risk is a 6: one named design flaw, confined to one model year, findable on a VIN check and covered by a free recall. The dollar dispute is context for that, not what decides it.

The inspection checklist

1. Confirm the model year: 2020, or 2021 and on. It decides whether the oil pump is a question at all
2. Cold start, and listen for oil pump whine
3. Scan for stored oil pressure fault codes
4. Look over the coolant tank for hairline cracks and coolant staining
5. Watch the temperature gauge through a full warm-up
6. Run the VIN for 21V-598, 23V584000 and 26V056000, and get proof 21V-598 was done on a 2020

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The Daily

Five seats, four doors and a 17 cu ft trunk. It answers the category's real question, whether it could be the only car you own, with a yes.

For the screens, the 2020 to 2022 cars use iDrive 7 on a 10.25-inch touchscreen with wireless CarPlay, and the 2023 facelift moved to iDrive 8 and a curved display. We have not sourced that line ourselves, so check it on the car you are looking at.

Against the Supra 3.0, this is the trade: the Supra seats two and carries 10.2 cu ft. Against the Golf R's 22.8 cu ft hatch, which earns a 9, a sedan trunk sits a rung lower on our rubric.

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The Limit

F Street, on the 2026 SCCA Solo rules. SCCA's own rules bulletin names the “3 Series (G20/21 chassis; 330i including xDrive, and M340i)” in Appendix A, and regional clubs class the car in F Street, but we could not load the rulebook itself to quote the class letter from it. It shares F Street with the G37 and the Charger R/T.

The hardware is what lifts it. The limited-slip differential is standard on both drivetrains, per BMW's own 2020 release, and the F30-generation 340i and 335i before it did without one. On our rubric the class line puts it at 6, competent and understeering first, and the differential adds one, for a 7. It runs staggered 225/40R19 front and 255/35R19 rear tires under 3,849 lb. We have no grip figure for it: the one we found comes from an outlet outside the sources we use. The Supra 3.0 has 1.02 g measured and an 8.

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The Mods

The first step is the same as on the Supra 3.0: an ECU flash tune, usually paired with a catless downpipe for the full gain. We price it at about $1,000 to $1,500 per +100 whp, and that is an estimate. It is carried across from the shared engine, where the Supra 3.0's figure is about $1,000 for a tune and downpipe taking it from about 337 to 420 whp. We found no independent dyno result for an M340i, and we left tuner marketing out.

Nothing we found ties tuning to the 2020 oil pump or the plastic coolant parts; those fail on stock cars too. That is a search that came up empty, not proof that tuning is harmless. The aftermarket is the Supra 3.0's: tunes, downpipes, intercoolers and intake parts built for the B58 largely fit both. Four figures for a transformation, on a bottom end that takes it, is a 9, the same score the Supra 3.0 holds on the same engine and the same first step.

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The Verdict

Buy a 2021 or later, or a 2020 with recall 21V-598 done by VIN, and price in about $4,068 a year going back to depreciation. It scores 46 out of 70: a 9 for the Mods, an 8 for the Drive and an 8 as a real four-door, held down by a Deal of 2, where you pay 2.03 times the going rate for its power and lose about 11.2% of the value a year.

Check the model year before anything else. Then run every recall by VIN, listen to a cold start, and look at the coolant tank.

This car is for you if you want the Supra 3.0's engine and its tuning headroom with five seats and a 17 cu ft trunk, and the depreciation is a cost you have planned for. It is not for you if you want six cylinders for less money: the G37 is $6,945 on book for 328 hp in the same F Street class, with a Mods score of 6 to this car's 9.

The Long Read: Should You Buy a Used BMW M340i (G20)?

We scored the M340i as a 2020-on G20 sedan with the B58 3.0-litre turbo six, the eight-speed automatic and rear-wheel drive, and it landed at 46 out of 70, with a verdict of Buy a 2021+, or a recalled 2020.

So you want a fast sedan you can put a family in. A used M340i gives you the Supra 3.0's 382 hp engine, a limited-slip differential and five seats for $36,360 on book. The repair to know about is confined to 2020 cars and covered by a free recall. What counts against it is the price, and how steadily that price keeps falling.

We scored the rear-drive car, priced on the 2022. BMW also sold it as the xDrive, which is about 119 lb heavier, and when we pulled the listings, rear-drive cars were the larger share of what was for sale.

How much does a used M340i cost?

Kelley Blue Book values a 2022 rear-drive M340i at $36,360 in Good condition private party, with its condition range running from about $34,260 to $37,860. Asking prices run well above that: the 13 rear-drive 2020-on cars on Cars.com when we looked asked a median of $48,587, from $30,501 to $58,287, or 1.34 times book.

Of the 23 listings in that pull, 13 were rear-drive and 10 xDrive. We had estimated the market at roughly 70-80% xDrive, and this sample points the other way. It is one snapshot, not a sales figure, but you will not struggle to find a rear-drive car.

How fast does the M340i depreciate?

Steadily. KBB puts a 2022 at about $52,676 in 2023 and $36,900 now, 29% in three years, which compounds to about 11.2% a year, or about $4,068 a year on the $36,360 buy-in. And the buy-in is already 2.03 times what 10.08 lb per hp usually costs across our Board, about $17,868. You pay above the going rate for the power and then keep losing it, which is why the Deal scores a 2.

What goes wrong with the M340i?

One thing worth knowing, on one model year. On 2020 cars the oil pump's pressure-relief ring is plastic and can fail, reported from roughly 30,000 to 60,000 miles. BMW moved to an all-metal pump for 2021.

What it costs is disputed, so here are both figures. One puts it at $6,000 to $8,000, with the front subframe coming off to reach the oil pan. Another estimate puts a straightforward pump replacement at about $2,100 to $3,000. We could not confirm either against an M340i shop quote.

Recall 21V-598 covers the 2020 cars, about 10,877 of them in the US. Software can damage the combined oil and vacuum pump and reduce brake assist, and dealers update the software and replace a damaged pump free. A 2020 with that recall done is a much safer buy, and a VIN check tells you. Two more free recalls reach the rear-drive car: a seat-belt chime software fix, 23V584000, and a starter that can overheat, 26V056000. Beyond that, expect the B58's usual coolant tank, water pump and gasket work.

Is the M340i expensive to run?

About $6,025 a year. Fuel is $1,846 at 26 mpg on 91-octane premium. Insurance is $2,808, on MoneyGeek's own row for the M340i sedan rather than a 3 Series average. Tires are $571 a year on our Board tire rule, on a staggered set of 19s that cannot be rotated front to back, and service is about $800, our estimate.

How does the M340i drive?

Quickly: 382 hp and 369 lb-ft in 3,849 lb is 10.08 lb per hp, through an eight-speed automatic and a limited-slip rear differential. We have no independent 0-60 time; BMW claims 4.4 to 4.5 seconds.

The engine is the reason to buy it, and we rate it as we rate the Supra 3.0's, a 5. The steering is electrically assisted, precise but numb, and we rate it a 3. The Supra 3.0 carries the same engine in 3,400 lb, which is why it scores a 9 for the Drive and the M340i an 8.

Can an M340i be your only car?

Yes. Five seats, four doors and a 17 cu ft trunk. The Supra 3.0 with the same engine seats two and carries 10.2 cu ft.

Is the M340i any good at autocross?

It runs in SCCA's F Street, alongside the G37 and the Charger R/T. What lifts it on our rubric is the limited-slip differential, standard on both drivetrains, which the F30-generation 340i and 335i went without. That makes its Limit a 7. We have no grip figure from a source we use.

Should you tune an M340i?

It is built for it. The first step is the Supra 3.0's: an ECU tune, usually with a catless downpipe, which is an emissions problem in some states. We estimate about $1,000 to $1,500 per +100 whp, carried across from the shared engine rather than measured on this car. The tuning parts are the Supra's too, and that is why its Mods score is a 9.

M340i buy or skip: the verdict

Buy a 2021 or later, or a 2020 with recall 21V-598 done by VIN, and price in about $4,068 a year going back to depreciation. Check the model year first, run every recall by VIN, listen to a cold start, and look at the coolant tank.

The M340i finished at 46 out of 70 on our Board. It loses points to a price at 2.03 times the going rate and resale falling about 11.2% a year. It wins them back with a 9 for the Mods, an 8 for the Drive, and five seats and a trunk you can live with every day.