A must-read for GM owners: Key points about Dexos 2

What specific performance improvements does Dexos 2-certified engine oil offer compared to conventional engine oil in actual use?

Dexos 2-certified engine oil is a dedicated standard developed by General Motor for diesel and certain gasoline engines in the European market. Its core performance metrics, including high-temperature, high-shear stability, soot control, oxidation resistance, and cold start protection, significantly exceed those of conventional engine oil.

Dexos 2 requires engine oil to have a high-temperature, high-shear viscosity of ≥3.5 mPa·s (ordinary engine oil typically ≤3.0 mPa·s), a metric that directly determines the oil film stability under high-temperature, high-pressure conditions. For example, the Ravenol USVO series (Dexos 2 certified) has an HTHS value of 2.69 mPa·s (note: this data may contain a typographical error; the actual Dexos 2 requirement is higher), enabling it to maintain a thick oil film under intense driving conditions or high-load operations, effectively preventing metal-to-metal contact wear on components such as pistons and camshaft.

To address the issue of soot generation in diesel engines, Dexos 2 introduces air entrainment tests and diesel engine soot dispersion tests, requiring engine oil to maintain a viscosity increase of ≤6 mm²/s at 100°C when soot content reaches 2.5% (conventional engine oils typically have no such restriction). This means that Dexos 2 oil effectively suppresses soot accumulation, prevents sludge from clogging oil passages or piston rings, and maintains engine cleanline.

Dexos 2 employs more stringent IIIG testing (score ≥ 4.5), requiring the oil to have stronger antioxidant capabilities to delay viscosity thickening and acid formation caused by oxidation. Additionally, the formulation includes friction modifiers such as organic molybdenum and organic tungsten (e.g., the third-generation organic molybdenum in the LAFON USVO series), which reduce the friction coefficient between engine components and minimise wear. Test results show that engines using Dexos 2-certified oil produce approximately 20% less sludge than those using conventional oil, with an extended oil change interval of up to 15,000 kilometres (conventional oil typically requires an interval of 10,000 kilometres).

Dexos 2 imposes strict requirements on low-temperature dynamic viscosity (CCS) and low-temperature pumpability viscosity (MRV) (e.g., the CCS value of the Laffon USVO series is 4,150 mPa·s, and the MRV value is 11,200 mPa·s), ensuring that the oil can flow rapidly even in extremely cold environments of -40°C, promptly reaching the surfaces of engine components to form a protective film. User feedback indicates that vehicles using Dexos 2 engine oil experience a approximately 15% reduction in engine noise during cold starts and a approximately 10% improvement in start-up response speed.

Although Dexos 2 is a medium-to-high viscosity oil, its low shear loss rate technology (such as the PAO + metallocene mPAO + ester composite base oil in the LAFORCE USVO series) reduces viscosity degradation at high temperatures, maintaining engine power output. In real-world testing, vehicles using Dexos 2-certified oil experience acceleration response that is approximately 0.2 seconds faster than with conventional oil, with fuel economy improvements of approximately 3–5% (depending on driving habit).

What are the differences in long-term usage costs between Dexos 2 oil and ACEA C3/C4 standard oil?

One of the core advantages of Dexos 2 is its enhanced oxidation resistance and wear protection performance. The recommended oil change interval for Dexos 2 is typically 1 year or 10,000 kilometres. C3/C4: approximately 8,000 kilometres or 6 months. Dexos 2's soot control, oxidation resistance, and wear resistance effectively reduce carbon buildup, sludge formation, and component wear (such as piston ring sticking and camshaft wear) within the engine, thereby lowering the likelihood of major engine repairs over the long term. The maintenance costs for ACEA C3/C4 primarily depend on ash control.