The 2023 US BMW X3 manual names BMW LC-18 coolant, identifies the engine and optional additional-radiator tanks, and explains cold filler-neck checks; compare its exact edition with 2022.
Scope: 2023 US-English BMW X3 G01 model-series owner's manual, original BMW part 01405A602E0 (VI/22), printed pages 360 and 367–368. The integrated VIN-specific manual is controlling for the individual engine, options and software; this is not an X3 M, 2025 G45 or universal BMW fluid instruction.
Do not open a hot pressurized BMW coolant reservoir. Escaping coolant can scald. Steam, a high-temperature warning, rapidly falling level or an active leak means stop safely, shut off the engine and seek qualified assistance; avoid fans that may run after shutdown.
The 2023 US X3 model-series Owner's Manual, BMW original part 01405A602E0 (VI/22), explicitly recommends coolant meeting BMW LC-18 on printed page 367. The previous 2022 US book, part 01405A38514 (VI/21), describes compatible additives and 50:50 water/additive mixing without naming LC-18 in its coolant section. This is a documented difference in *wording* across manual editions, not proof that all 2022 X3s need a different coolant or that a prior factory fill must be replaced.
Both editions warn against mixing coolant additives of different colors and describe a 50:50 water-to-additive proportion. Check the current integrated Owner's Manual and the vehicle's BMW-approved specification before adding anything; a broad internet model-year chart cannot establish fluid compatibility for an individual VIN.
On printed page 360, BMW's 2023 engine-compartment diagram labels item 3 as the engine coolant reservoir, item 4 as the coolant reservoir for an additional radiator **depending on motorization**, and item 6 as the washer-fluid filler. It also shows item 7 as the vehicle identification number location. These are diagram reference numbers, not service part numbers.
Printed page 368 says that up to two reservoirs may exist and that the side of the engine bay on which a reservoir is positioned depends on motorization. The 2022 book likewise distinguishes the engine and additional-radiator reservoirs, so the 2023 model year does not establish a new universal tank layout.
The 2023 book's coolant section on printed pages 367–368 directs owners to let the engine cool before inspection. It places minimum and maximum markings within the reservoir filler neck. The manual also warns that opening a hot system can release scalding coolant; outside markings or a photo of another model's tank are not substitutes for the proper procedure.
BMW notes that new vehicles can initially appear overfilled at delivery, with the normal level reached after more operation. That statement is not reassurance that recurrent coolant loss, steam or an overheating message is normal. If the level is repeatedly dropping, source confirmation is needed.
No. An X3 coolant warning, wet connection or low filler-neck reading does not independently identify a cracked tank, failed cap or defective hose. The 2023 BMW book asks that the cause of coolant loss be eliminated promptly; this requires qualified diagnosis of the actual cooling circuit, particularly on variants with an additional radiator reservoir.
Before buying a tank, request a verified origin, VIN-matched part, correct reservoir/cap configuration, approved coolant and post-repair check. The owner manual does not provide a universal leak frequency, replacement-part number, pressure-cap rating or hose torque.
These outbound sources support the stated facts and precautions within their listed scope. This article does not claim independent hands-on service testing or replace a manufacturer's workshop procedure.
Original BMW 2023 US-English publication with page 360 engine/optional radiator/washer diagram; p.367 explicit BMW LC-18 recommendation and hot-cap warning; p.368 up to two reservoirs and filler-neck cold MIN/MAX.
Official vehicle-specific reference for checking whether a model-series illustration, additive recommendation or option actually applies to the individual car.
Adjacent original manual, pp.359 and 366–367, documents compatible coolant additives and 50:50 ratio without naming LC-18 in its printed coolant section; difference in wording is not automatic interchangeability.
