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F30 Common Problems by Engine
How reliable each F30 really is — the N20's timing chain, the turbo N55, the modular B48 and B58, and the diesels, plus the issues they share and which engine to buy.
Read the guide →N20 Timing Chain Explained
The signature N20 issue, demystified — the timing chain, the separate oil pump chain, and the plastic guides, and why all of it is replaced together.
Read guide →335i Common Problems (N55)
The pre-LCI turbo six — the N55, its known quirks and what to check before buying. In the works.
Coming soon340i & the B58
Why the B58-powered 340i is widely considered the one to have — and what little there is to watch. In the works.
Coming soonBuying
DIY Guides
Oil Change by Engine
The routine service done right — the correct oil and capacity for the N20, N55 or B58, the top cartridge filter and the electronic level (no dipstick).
Read guide →Water Pump & Thermostat
The electric pump and thermostat, including the electronic bleed. In the works.
Coming soonFront Brake Pads & Rotors
Pads, rotors and the wear sensor up front — the easy half, since the electronic parking brake is on the rear. (Rear, with EPB service mode, coming.)
Read guide →Spark Plugs & Coils
Coil-on-plug by engine — the right plug, gap and interval for the N20, N55, B48 and B58, the colder plug a tuned turbo wants, and misfire diagnosis.
Read guide →Oil Filter Housing Gasket
The F30's classic oil leak — diagnosing and resealing it. In the works.
Coming soonCabin Air Filter (5 Minutes)
The easiest win on the car — swap the cabin microfilter under the hood, no tools, in about five minutes.
Read guide →Battery Replacement & Registration
The trunk-mounted swap — and the all-important registration step that makes the new battery last.
Read guide →Ownership
Parts & Brands
Best Oil (N20 / N55 / B48 / B58)
The right LL-01 / LL-17 spec for your engine, and when to step up for a tuned turbo. In the works.
Coming soon