Overview
Stock power and torque
B48 stock: 248–322 hp depending on tune and chassis (320i: 180 hp; 330i: 248 hp; M135i/Supra 2.0L: 304–322 hp). B58 stock: 320–382 hp. The B58 has the power headroom; the B48 has the fuel-economy headroom.
Fuel economy
B48 is meaningfully better: EPA combined 28–32 mpg in 320i/330i, vs B58 24–26 mpg in M340i. Real-world difference: ~3-5 mpg on mixed driving. If your commute is mostly city, the B48 wins on fuel.
Common faults compared
B48 issues: timing chain stretch (a known issue on early B48 production — the chain can stretch enough to throw a timing code; replaced under warranty but not on every car), oil filter housing gasket leak, VANOS solenoid clogging (less common than N55, same fix). B58 issues: VANOS solenoid clogging, vacuum pump leak, thermostat housing (early production), no timing chain issues. The B58 has fewer common faults than the B48.
Tuning headroom
Both engines tune well. The B48 is a 2.0L turbo with strong aftermarket (the Supra 2.0L community is particularly active); 350–400 hp is achievable on stock internals with a tune + downpipe + intercooler. The B58 tunes higher: Stage 2 is 420–480 hp reliably.
Cost of ownership
B48 parts are slightly cheaper (smaller engine, simpler service). B58 spark plugs are more expensive (6 vs 4). Oil change: B48 ~5L, B58 ~7L. Real-world difference at 100k miles is a few hundred dollars — not a deal-breaker.
The decision
B48 is the choice for fuel economy, lower upfront cost, and a lighter front end. B58 is the choice for power, smoother six-cylinder sound, and longer-term tuning headroom. Both are good engines; the right one depends on what you want from the car.
FAQ
Which is more reliable, B48 or B58?
B58 has fewer common faults. The B48’s timing-chain stretch on early production is the headline concern; the B58 doesn’t have an equivalent issue. Both are reliable engines.
Which is faster, B48 or B58?
B58, by a meaningful margin. 382 hp stock vs 248 hp stock. The B48 can be tuned to 350–400 hp but the B58 starts higher and has more headroom.
Is the B48 the same engine as the Mini Cooper S?
Yes. The MINI Cooper S F56 uses the B48. Same engine, different tune and packaging.
Is the B58 the same as the Toyota Supra engine?
Yes. The Supra 3.0L uses the B58. BMW designed and built the engine; Toyota integrates it with the chassis.