The inline six (or straight six) engine has been a perennial staple of Japanese tuner culture since the 1980s, particularly with Toyota. The megacorporation’s flagship sports car, the Supra, practically had its identity built around its infamous powertrains since day one, and that’s no accident. Toyota’s original design criteria called for the Celica Supra to have an elongated front end suitable for a straight six; every single generation of Supra that came after received straight six engines.

Of course, many other Toyotas have used straight sixes before and since, and that includes the venerable 2JZ; but the company has slowly and silently phased them out one by one until there was one remaining: the Supra. And now that its production is over, so too has Toyota’s straight six legacy — at least for now, or so we hope. But that statement’s only half-true; while the Supra may have boasted the famous Toyota badge and nameplate, it was actually developed as part of a joint venture with BMW, meaning the final Toyota straight six wasn’t even powered by a Toyota engine. It was instead powered by a BMW engine, or at least a partly BMW-branded one, specifically a B58 — the same engine as the M340i.

That partnership resulted in an engine that punched above its weight, and despite the trolls saying, “No no, it’s a BMW,” the truth is that the engine itself, as well as the car as a whole, was co-developed by both firms. It was a venerable, muscular powertrain that unfortunately sunsetted for Toyota in 2025 with the end of the partnership. Let’s discuss the engine itself and what happened that caused its demise.

First up, let’s get the specs out of the way. The vehicle we’re discussing is the 2026 Toyota Supra Final Edition, which comes in multiple trim levels depending on region. The U.S. market example has no differentiation with the regular production Supra in terms of power figures, with the engine producing 382 hp and 368 lb-ft torque. For domestic Japanese and the European markets, however, Toyota launched what it calls a “partially upgraded model” which boosts power to 429 horsepower and torque to 420 lb-ft.

The original configuration of the engine bears the model number B58M30O1 found under the hood of six cylinder-equipped A90s. Various BMWs use what’s effectively the same B58, though different engines have their own individual parts and configurations, even within BMW’s lineup. The Supra’s iteration isn’t even the most powerful, with BMW squeezing out over 500 horsepower with the M-spec S58 variants.

That said, the Supra’s engine remains quite stout. Toyota’s upgrades center around optimized air flow, providing the Supra with an optimized intake air path and a low back-pressure catalyst within the exhaust. This minimizes airflow being blocked up by the catalytic converter like a dam and shooting back into the combustion chamber, a particularly important factor when you’re at high RPMs and the air needs to flow quickly. Toyota then tuned the engine for these newer parameters, finalizing the engine with its peak horsepower occurring at a healthy 6,000 RPM according to the dyno sheet. We absolutely loved this engine in the Supra, particularly when paired with a manual transmission.

Because the engine was employed as part of a partnership agreement that’s now ended, we’re not likely to see the B58 in anything else other than a BMW. Granted, that doesn’t mean that we’ll never see another Toyota straight six; stranger things have happened, like Mazda resurrecting the Wankel rotary to power concept cars and as a hybrid power generator, of all things.

Plus, we must consider that the Supra wasn’t the only car Toyota powered with a straight six; the engine is exceptionally smooth and simple, lending it well to luxury-oriented vehicles and forced-induction applications, as we’ve seen on the B58 itself. That said, straight sixes, including the B58 in the Supra, also come with various downsides. The first and most obvious is that they’re far longer than V6 engines, meaning they don’t pack as nicely into an engine bay and may face rigidity issues. 

Ultimately, with the Supra retired, that leaves Toyota without a horse in the mid-market sports car race; the new GR GT boasts numbers on-par with modern supercars, and will likely be priced accordingly. Where does that leave us? Put simply, Toyota would have to engineer a car from scratch to accept a straight six, which is certainly possible, though not particularly likely unless the company commits to building multiple models across a broader spectrum — think the 1990s and 2JZ in various Toyota and Lexus models. While we can certainly dream of such a renaissance, we won’t hold our breath.