For BMW M240i owners, ensuring peak performance and longevity hinges on several factors, and engine oil selection stands out as paramount. In recent years, a critical specification known as High Temperature High Shear (HTHS) viscosity has gained prominence, directly impacting both fuel efficiency and engine protection. Understanding HTHS is crucial for choosing the optimal oil for your M240i Engine.
HTHS viscosity measures an engine lubricant’s resistance to flow under severe conditions: elevated temperatures of 150°C and constant shear, mimicking the intense environment within a running engine, particularly in tight clearances and high-speed movements. The lower the HTHS viscosity, the less resistance the oil offers, translating to improved fuel economy. However, a balance must be struck as HTHS viscosity also plays a vital role in engine durability.
The unit for HTHS viscosity is millipascal seconds (mPas). Oils are generally categorized based on their HTHS value. A ‘normal’ HTHS viscosity is considered to be above 3.5 mPas, typically found in older specifications. In contrast, a ‘reduced’ HTHS viscosity is below 3.5 mPas, a characteristic of newer, fuel-efficient engine oils. While lower HTHS oils enhance fuel efficiency, higher HTHS oils generally provide a thicker oil film and potentially better protection for engine components under demanding conditions.
BMW, like many manufacturers, now incorporates specific HTHS viscosity ranges into their oil specifications. Let’s examine how this applies to your M240i engine and relevant BMW Longlife (LL) oil specifications.
Recent updates in oil specifications have brought about distinctions like LL17FE and LL12FE. LL17FE specification mandates an HTHS of ≥ 2.6 mPas. To meet this low HTHS requirement, only SAE 0W-20 viscosity oils are typically suitable. The slightly higher LL12FE specification requires an HTHS of ≥ 2.9 mPas, allowing for the use of both 0W-20 and 0W-30 oils. Both LL17FE and LL12FE are categorized as low HTHS oils, prioritizing fuel economy for modern engines like the M240i engine.
For comparison, older BMW oil specifications such as LL01 and LL04 demand a higher HTHS of ≥ 3.5 mPas. Even the LL01-FE, an earlier fuel-efficient specification, had a minimum HTHS of ≥ 3.0 mPas. Furthermore, to illustrate the trend towards fuel efficiency, SAE 0W-16 oils often feature an HTHS around 2.3 mPas, pushing fuel economy even further.
While HTHS viscosity is a critical factor, it’s just one piece of the complex puzzle of engine oil formulation. Choosing the correct oil for your BMW M240i engine involves considering the BMW Longlife specification recommended for your vehicle, and understanding the role of HTHS viscosity within those specifications is key to optimizing both fuel efficiency and engine protection. Always consult your BMW owner’s manual or a trusted BMW service professional to ensure you are using the correct engine oil for your specific M240i model and driving conditions.
