Understanding GM’s dexos1™ PCMO specification
Like all automakers worldwide, General Motors is working on new engine technologies in response to legislative and public demand for lower emissions and better fuel economy.
Manufacturers are downsizing engines and incorporating features such as gasoline direct injection (GDI) and turbocharging to optimize fuel consumption. These smaller, lighter engines tend to run hotter and are under more stress than older engines, meaning they need stronger protection. The auto industry has called upon oil producers like Chevron to develop new oils that address these evolving demands.
In 2010, GM introduced its dexos1™ oil specification, then upgraded it in 2015. The more stringent dexos1 2015 standard, also referred to as dexos1 Gen 2, sets forth the requirements for developing oils that can be used with today’s advanced engine technologies. Approved dexos1 oils will be mandatory for both factory fills and service fills starting with 2017 and 2018 GM models. Oils formulated to meet dexos1 specifications are also backwards-compatible with older engines.
The specification requires that oils meet several of the industry’s most demanding tests, as well as newer tests specific to GM’s requirements. Although GM and other manufacturers are designing engines to be more efficient, a few unforeseen hardware challenges have emerged. Oil producers and our chemical additive suppliers have been collaborating with engine OEMs to address these issues.
A big concern for GM, and much of the impetus behind the dexos1 standards upgrade, is “low-speed pre-ignition” or LSPI. This refers to an abnormal combustion event in which the fuel-air mixture ignites before intended, causing excessive pressures inside the engine’s cylinders. The higher power density of turbocharged, GDI engines makes them vulnerable to LSPI. In mild cases, LSPI causes “super knocking” noises, but in more severe cases it can cause engine damage. Turbocharger failures due to deposits and oil oxidation are another issue. These result in inefficiencies in the engine and can result in a loss of power and acceleration.
Choosing the right motor oil plays a critical role in mitigating these challenges. The dexos1 Gen 2 oil specifications include rigorous GM-specific testing for protection against LSPI, turbo deposits and oxidation, as well as for vehicle fuel economy and aeration. Only the top performing oils in these tests earn dexos1 approval.
With dexos1, GM has raised the bar and challenged the PCMO industry to step up its game, delivering new products that address the demand for lower emissions and higher fuel economy. GM owners can feel confident they are using a high-quality motor oil with the latest technology, specifically designed to protect GM engines and help maximize their performance. The great thing for consumers and professional installers is that oils that meet dexos1 specifications, such as Chevron’s Havoline ProDS® Full Synthetic, are not strictly “GM oils.” Because they exceed other manufacturers’ requirements, they can actually be used in a variety of applications, including many domestic and imported new model cars. As always, consult the OEM’s manual for specific oil recommendations.