dexos 1 vs. dexos 2- What is GM dexos Oil?
Auto manufacturers really like to create their own rating systems for various fluids that are used in their vehicles. Ford has special grease formulations for their suspensions, BMW requires very specific power steering fluid, and GM has their own oil rating system, dexos. The dexos oil rating was created in 2010, updated in 2015 and now includes dexos 1, dexos 2, and dexos D. These ratings are currently very specific, each rating only covers one or two grades each. These oils are NOT sideways compatible, meaning you shouldn’t use dexos 2 in a dexos 1 engine.
What is dexos oil?
GM’s engine development engineers needed a specific formulation of oil for the new GDI (Gasoline Direct Injection) engines, beginning in 2011, all GM gasoline engines required dexos 1. This is a special formulation that has superior sludge control, aeration, wear, low-temperature performance, and deposit formation. The main issue for GM was that when they examined their global engine platforms, they realized they had quite a few oil specs for various engines and this caused a number of issues for GM in terms of what oil to use where.
Even though GM is a member of ILSAC (International Lubricant Specification Advisory Committee) and helped develop the API GF-5 and SN oil grades, they felt a need to create a global GM oil rating system. This resulted in dexos, which allowed them to issue simplified guidelines on oil properties, change intervals, etc. What began as dexos 1 in 0W-20 only, now has dexos 2 and dexos D, along with 2 updates to dexos 1. The issue at hand is that ILSAC and API rating changes are very slow, as they rely on input from every engine manufacturer, so there is a lot of information and not much action. GM realized they simply can’t wait for these committee units to make the changes they needed, so they came up with the dexos system.
Is dexos oil full synthetic or synthetic blend?
AC Delco brand dexos 1 oils are a synthetic blend, using both synthetic and conventional base oils, but there are both full synthetic and synthetic blends available in all types of dexos rated oils. There are no conventional (non-synthetic) dexos rated oils.
What is dexos 1?
If you own a GM gasoline engine, regardless of size, built after 2011, then GM requires an oil that is dexos 1 rated. This is a global rating and developed for the new 0W-20 grade. Up until 2011, this grade was not used in domestic engines in the United States, though it did in Japan. To bring this grade into the US, GM made it their only recommended oil grade for their gas engines in the dexos 1 system. This grade of oil is the only recommended grade for the Gen V LT-series direct-injection engines.
In 2015, GM updated the dexos 1 rating to Gen 2 (this is NOT dexos 2, it is still dexos 1). GM also added low-speed pre-ignition and aeration resistance testing for the oil. This is critical because VVT (Variable Valve Timing) uses engine oil as if it were a hydraulic oil, which it isn’t. If air gets into the VVT system, it drastically reduces performance. In addition to the API GF-5 testing, dexos 1 also includes the ACEA Europe testing profile as well, which is required to make dexos a global system. All dexos testing standards are stricter than API limits.
As engine technology moves toward even stricter EPA requirements, GM released the Gen 3 rules for dexos 1 to further manage oil properties in a global system. Gen 3 dexos oils (commonly referred to as “dexos 1 Gen 3”) have been adjusted to include turbocharger cleanliness, turbo coolant control, and oxidation. For example, Gen 2 limits for deposit formation are 100 max/5.2 min, while Gen 3 reduces those limits to 75 max/5.3 min., and turbo deposits went from 13% maximum increase in deposits to 11% maximum deposit increase. Even the fuel economy increases with the dexos 1 Gen 3 formulation. dexos 1 is for gasoline engines only, this is not designed for diesels. It is backwards compatible with older GM engines. dexos 1 is available in 0W-20 and 5W-30 grades.
What is dexos 2?
DO NOT confuse dexos 2 with dexos 1 Gen 2. It is not the same. dexos 2 is for GM’s light-duty diesel engines, such as the Chevy Cruze Turbo Diesel. It is also used in GM’s European gas engines. dexos 2 is spec’d in the US for the C8 Corvette. The goal for dexos 2 was to be developed primarily for diesel applications and non-turbo gasoline engines. This is an important distinction, because gas and diesel turbocharged applications are different, even though the components are similar. Soot production in a diesel engine is the biggest killer, and dexos 2 was formulated to reduce soot with lower ash content. dexos 2 also has a higher high temp sheer viscosity, which is part of diesel oil formulations.
European specs are different than US specs, and even though dexos 1 was developed to be a global system, GM’s dexos 2 is the European spec for all GM engines that are not Duramax diesels. The main reason that dexos 2 is the recommended GM gasoline-engine oil in Europe is because there are far more light-duty diesels in Europe than gas engines, so GM opted to use dexos 2 exclusively in Europe. dexos 1 is the recommended gas-engine oil in the US. dexos 2 is available in 0W-30, 5W-30, and 5W-40 grades.
What is dexos D?
The outlier in the GM dexos oil family is dexos D. This is GM’s newest dexos rating, and it is specifically designed for the light-duty Duramax diesel engines such as the LM2 3.0 liter. dexos 2 is NOT suitable for use in Duramax diesels. dexos D is available in 0W-20 grade. Do not confuse dexos D with GM’s Duramax Heavy Diesel oil, which is only for use in the large 6.6l Duramax diesel engines.
What brands of oil are dexos?
So now you know you need it, what brand of oils are dexos rated? Just about every brand of oil available in the US has a dexos 1 oil in Gen 2 or Gen 3; it is easy to find. All the major brands carry a dexos 2 line as well, but it can be harder to find. dexos D is more difficult to find, there are only 11 options from 8 bands that are currently making oil with the dexos D rating.
What is the dexos oil equivalent?
While GM recommends only using dexos rated oils in all 2011 and up GM vehicles, they cannot legally require it. For gasoline engines, this means that any oil with the latest API rating of SN or SN Plus will meet the general specifics for a 2011 and later gas engine. What you do not get are the more stringent ratings that is required for dexos approval.
What happens if I don’t use dexos oil?
There could be reduced performance in some circumstances. This is an “at your own risk” situation, where you are taking the risk of using non-dexos rated oil in your GM engine. It is unlikely that catastrophic damage will occur if you use SN oil in place of dexos 1 in your 2011 and newer GM gas engine.
Can you mix dexos with regular oil?
Can you? Yes. Should you? No. All dexos-rated oils are synthetic or synthetic blends, and this is done for multiple reasons, mixing conventional oil with dexos eliminates the benefits and performance of the dexos oil. Typically, dexos oils cost more than non-dexos rated oils, so while you can mix a regular oil with dexos, it is not recommended as it just lowers the quality of the oil in your engine. In an emergency, yes, you can safely top off your engine with a non-dexos formula, provided it meets the API SN rating and is of the same weight (0W-20 to 0W-20 for example).
In the end, modern engines are not as simple as they were just 25 years ago. They have to manage a lot of different tasks while still being good at moving the car down the road. Internal systems like VVT, active fuel management, and particulate filters are all affected greatly by the type of oil that is in the engine. GM recommends their specific rating system for a reason, and that is to ensure that the internal components and exhaust components operate at maximum efficiency. Opting to not run the recommended oil is one at your own risk. New vehicles cost $40k or more, spending a little extra on a dexos-rated oil that is recommended is probably worth the insurance.