In mid-2011, Police Fleet Manager ran a series of articles on semi-synthetic and full synthetic motor oil. The advantages in police work are clear. Synthetic oil offers better engine protection during a cold start, when 60 percent of engine wear takes place. See the March-April and July-August 2011 issues of Police Fleet Manager. Or go online at www.hendonpub.com, Resources then Article Archives.
Synthetic oil also offers better protection in extreme cold, extreme heat, and during periods of extended idling. Synthetic oil increases the oil change interval to between 10K and 12K miles. Synthetic oil costs more than conventional petroleum oil. However, with the extended drain interval, synthetic oil is actually a cost savings of around $110 per vehicle per year.
Get up to speed on synthetic oil because most 2011 and new GM vehicles require the use of dexos™ motor oil. Oil meeting the GM dexos oil spec are essentially synthetic oil. The official GM pitch is that the quality of the engine oil is a “crucial component of performance, longevity and environmental sensitivity…yet in today’s market, it is not always possible to determine the quality of the oil you buy.”
dexos is not a brand of oil. Instead, it is an engine oil specification. “dexos is designed to increase the fuel efficiency, extend the life of your emissions system, require fewer oil changes, and produce fewer emissions.” Any synthetic oil will do all that compared to conventional motor oil, so think of the dexos spec as a requirement to use synthetic oil.
Again, as GM rolls out the requirement for dexos-grade oil, they also remind us of the teeth in their engine warranty. GM vehicles, and that includes police package and special-service package vehicles, have a five-year, 100,000-mile limited powertrain warranty. However, if the engine failure can be traced to oil or lubrication issues, and the engine was not using a dexos1 oil, the engine warranty could be voided. (Yes, they can tell.)
To the point, straight from GM, oil that does not meet the dexos spec, that does not have the dexos icon on the label is “not approved or recommended for use in GM vehicles.” dexos is fully backward-compatible and can be used in older vehicles.
Not just any synthetic oil meets the dexos spec and carries the dexos icon. Again, dexos is not a brand of oil, it is a licensed oil. That means many different brands of oil may meet the dexos spec. Those that do will have a green dexos1 (gasoline) icon or blue dexos2 (diesel) icon on the label.
The dexos spec is not achieved by just any semi-synthetic or fully synthetic oil. To pass the dexos spec, GM requires the oil to pass proprietary tests not included in current industry standards. GM has also set some performance criteria at a level that exceeds many current standards. Again, it is not GM’s oil. It is oil that meets GM’s spec. The dexos spec is a combination of five prior recommended specs.
In some cases, the synthetic motor oil already meets the dexos spec. Think Mobil 1. In other cases, a tiny amount of expensive molybdenum needed to be added for increased anti-wear control. This element may be in addition to, or in place of zinc, the most common anti-wear compound.
The list of licensed oils is updated periodically, so check the website. Some popular brands of oil you might have guessed would be on the approved list are, in fact, not on the approved list. Since dexos is a licensed product, there is a cost to the oil manufacturer to display the dexos icon and trademark on their label. Some brands of oil are reluctant to license their oil Valvoline, for the time being, is one.
Thom Smith, Valvoline’s vice president of branded lubricant technology told Edmunds.com, “Our SynPower 5W20 and DuraBlend 5W-30 went through all the dexos testing and passed all the requirements. But we felt that carrying the dexos name was not providing the customer with any value. Rather than to raise the price of the oil to offset the cost of licensing the dexos name, Valvoline chose to forgo the license and keep the prices lower.”
The GM dexos spec is merely a year or so ahead of the oil industry’s new GF-5 oil spec. GF-5 will replace GF-4. These specs are developed by the International Lubricants Standardization and Approval Committee (ILSAC) with input from automakers, oil refiners and additive makers.
For those more familiar with the American Petroleum Institute (API) rating system, the new ILSAC GF-5 will carry an API “SN” label.
The move to synthetic oil was coming anyhow. GM dexos just got the jump on the rest of the industry. The new GM dexos, ILSAC GF-5 and API SN oils are superior in almost every way to conventional, non-synthetic motor oil.
The GM dexos oil has one spec that ILSAC and API labeled oils do not have. This is quite important! That dexos requirement is for better resistance to aeration, which is the whipping of air bubbles into the oil. Engines with variable valvetrain (variable camshaft timing) technology use engine oil as a hydraulic fluid to move components in the engine, i.e., hydraulic lifters.
If air bubbles are in the oil, the lifters will not act as fast as the engine controllers expect. On the mild end, this can limit engine performance and economy. On the extreme end, this slow response can throw a MIL or DTC check engine code. Chevy, Dodge and Ford police vehicles all use engines with a variable valvetrain timing!
For all practical purposes, put Mobil 1 in all GM police vehicles. The use of synthetic oil has always been a good match for how we use our vehicles. Now, according to GM, it is a requirement.
Partial List of Motor Oils with the dexos Icon and Trademark
Castrol Edge Professional
Mobil 1 Extended Performance
Pennzoil Synthetic Blend
Pennzoil Platinum Full Synthetic
Quaker State Synthetic Blend
Quaker State Ultimate Durability Full Synthetic