Best used executive saloon 2026: BMW 5 Series vs Mercedes E-Class vs Audi A6 e-tron

Here is the uncomfortable truth that should shape every used executive saloon purchase in 2026: the Audi A6 e-tron that Autocar rates as the most accomplished electric executive saloon on sale is also the one I’d be most nervous about buying second-hand. It carries a £63,300 starting price when new and a boot that holds just 326 litres. For a private buyer hunting a premium saloon on the used market, those two numbers tell a story the glowing reviews do not.

So let me lay out where I actually stand on the big three German executive saloons, BMW’s 5 Series, the Mercedes E-Class and the Audi A6 e-tron, because the car that reviews the best and the car that makes the smartest used buy are rarely the same thing.

The new prices that set your used benchmark

You cannot judge a used deal without knowing where the car started. New, the 5 Series opens at £52,300, the E-Class at £56,670 and the A6 e-tron at £63,300. That £11,000 spread between the cheapest and dearest is the single most important figure here, because depreciation works on a percentage of the original list price, and the further a car has to fall, the more of someone else’s money you can pocket by buying it a couple of years down the line.

Put rough numbers on it. A car shedding, say, 50% of its list price over three years loses around £26,000 on the 5 Series, near £28,000 on the E-Class and roughly £32,000 on the A6 e-tron, and it is the second and third owners who collect the difference, not the person who bought new. That is the whole logic of buying a premium saloon used: you let someone else absorb the steepest part of the curve, then step in. The catch is that the percentage isn’t fixed. A strong, in-demand model holds its money better, so a desirable 5 Series may actually shed a smaller share than a slow-selling rival, which is precisely why the cheapest-new car can still be the canniest used buy.

It also reframes how you read the reviews. The 5 Series sits below the E-Class on price yet What Car? still rates it as the executive saloon to drive, while the A6 e-tron earns its plaudits in a different, pricier electric league. Already the best-reviewed car and the best buy are pulling apart.

BMW 5 Series: the one I’d actually chase

The 5 Series is where my money goes, and it isn’t close. The lowest new price of the trio at £52,300 and a properly usable 520-litre boot make it the saloon that asks the fewest compromises of a real owner. What I like most is that none of its strengths are exotic, it is simply good at the boring, daily things an executive saloon is bought to do.

The 5 Series isn’t the most expensive or the most electric of these three. It is simply the one that asks the fewest compromises of a real owner, and on the used market that is worth more than any badge of honour.

For a used buyer, the maths is the clincher. A car that lists lower new and holds a strong reputation tends to sit in a sweeter spot on the depreciation curve: you are not subsidising a £63k sticker, and steady demand for a well-regarded 5 Series keeps the cars moving. If you want one premium German saloon to live with and not think about, this is it.

Mercedes E-Class: buy it for the ride, not the badge ego

The E-Class is the comfort specialist of this group: its serene ride quality prioritises calm over corner-carving, and that is exactly what a long-distance executive buyer often wants. It also has the biggest boot of the trio at 540 litres in non-PHEV form, twenty litres up on the BMW.

So who is the E-Class for? The buyer who spends more time on the motorway than the back roads, who values a hushed cabin and luggage space over the last tenth of driving sharpness, and who is willing to pay the £56,670-from-new premium that comfort buys. On the used market its higher new price means it has further to fall, which can make a two or three-year-old example look like genuine value if the ride suits you. Just go in knowing you’re buying the sofa, not the sports kit, and read the full picture in What Car?’s E-Class verdict before you commit.

Audi A6 e-tron: the early-adopter’s gamble

This is the one that splits the room. On its own terms the A6 e-tron is superb, capable of up to 460 miles of electric range, a figure that puts a lot of range anxiety to bed. If your driving is electric-first and you want the most accomplished electric executive saloon on sale, it earns its crown.

But I’d think hard before buying one used in 2026. Two things give me pause. The first is that 326-litre boot, a meaningful step down from the 5 Series’s 520 and the E-Class’s 540, and a real-world dent in the practicality you expect from a car this size. The second is price exposure: £63,300 new is a long way to fall, and used electric values have been the most volatile corner of the market. That volatility cuts both ways, it can hand a brave buyer a lot of car for the money, but it can also leave you holding a fast-depreciating asset in a fast-moving segment.

The A6 e-tron is therefore the connoisseur’s pick: right for the committed EV driver who values range and cabin tech over outright boot space, wrong for the buyer who wants a safe, predictable used purchase.

The saloon I’d sign for

My order of preference is the 5 Series first, the E-Class for comfort-led buyers, and the A6 e-tron for committed EV drivers only. Three things would shift that. If you cover serious motorway mileage and rate calm above all, the E-Class jumps the BMW. If your life is genuinely electric and you can charge at home, the A6’s 460-mile range and tech make it the head choice despite the small boot. And if a used A6 e-tron has fallen far enough on price to absorb its own depreciation risk, the early-adopter gamble starts to look like a bargain hiding behind a scary new sticker.

But for the buyer who wants the closest thing to a sure bet, a premium German saloon that does everything well and costs less to begin with, the 5 Series is the car I’d be putting a deposit on. It might not win every road test. As a used buy, I’d argue it wins the one that counts.