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Synthetic Oil and Operating Costs

Written by Ed Sanow

The way police vehicles are used, synthetic oil and semi-synthetic blends are genuinely superior to conventional motor oil. Synthetic oil may lower the total operating costs of your fleet. Longer oil change intervals mean lower preventive “maintenance” costs. Because the advantages of synthetic oil exactly match the police duty cycle, lower “repair” costs and longer engine life are also possible. About 60 percent of engine wear (rings, bearings) occurs on the cold start—synthetic oils have a clear advantage here.

Synthetic motor oil is not new. Synthetic oil for aircraft engines dates back to the early 1940s. The first synthetic oil developed for car engines was produced by Amsoil-Hatco in 1972. However, it was Mobil Oil that popularized synthetic motor oil with its Mobil 1 in 1974. The Corvette and Cadillac come from the factory with synthetic oil. So do Porsches and the AMG versions of the Mercedes. Remember the recent fix to the Ford CVPI axle bearings? Synthetic oil. Today, virtually every brand of petroleum oil includes synthetic or semi-synthetic oil.

The primary advantage of synthetic oil is resistance to heat breakdown. Synthetic oil does not break down as quickly, so it lasts longer, allowing for extended oil change intervals. At a time when automakers were recommending petroleum oil changes every 3,000 miles, synthetic oil changes in retail cars were performed at up to 15,000 miles.

No question about it—synthetic oil is absolutely perfect for police use. Severe service fleet use plays right to the strengths of synthetic oil. Those strengths include better performance than petroleum oil under hot operating temperatures, during extended idling, during cold starts, during stop-and-go driving, and during extremes of hot and cold driving conditions. Synthetic oil is better than motor oil in virtually every standardized (ASTM) test for motor oil.

What Makes Oil Synthetic?

The definitions for synthetic have changed. The term “synthetic” used to mean non-petroleum based oil, i.e., an oil “synthesized” from something other than crude oil. The purest, most original definition was that synthetic oil was made from Poly-Alpha-Olefin (PAO) base stocks. Synthetic oil (PAO), the “real” synthetic, the original synthetic, is an API Group IV oil. For years, no petroleum-based oil could match the performance of Group IV PAO synthetic oil. Then the technology changed.

The American Petroleum Institute (API) categorizes oils based on their chemistry and/or how much refining of the crude has been done. API Group I base stocks are conventionally distilled petroleum. API Group II is petroleum that has been hydro-cracked, a process developed in the early 1960s by Chevron. Most standard or conventional motor oil today is Group II.

API Group III base stocks are the cause of all the synthetic oil confusion. Group III oils are Group II oils that have been hydro-cracked again or hydro-isomerized to further refine them. Group III oils have much higher viscosity indexes than Group II oils; as a result, these Group III oils are also called Very High Viscosity Index (VHVI) oils. Both Group II and Group III oils, however, are still very much petroleum based.

ASTM has a test that measures how much the viscosity (thickness) is affected by temperature. The higher the Viscosity Index, the less the oil thickens as it gets cold, and the less it thins out as it gets hot. The culprit is a form of wax. Advanced dewaxing technology is essentially what turns a Group II petroleum base stock into a Group III petroleum that can be called synthetic. In other words, Group III petroleum oils now have much higher viscosity indexes than Group II conventional petroleum oils. In fact, these Group III petroleum VHVI petroleum oils rival Group IV PAO synthetic oils.

Hydro-cracking Technology

Chevron was the first to perform hydro-cracking, and it introduced iso-dewaxing of petroleum oil. That is the essence of Group III VHVI petroleum oils. Chevron later merged with Conoco Phillips, a company that also makes Group IV PAO base stocks. Its motor oil is branded Kendall GT-1.

Castrol SYNTEC was originally made from API Group IV PAO base stocks, i.e., SYNTEC was a “true” synthetic oil. In 1997, Castrol changed the formula for its PAO-based, full-synthetic SYNTEC oil. It switched from a Group IV Poly-Alpha-Olefin (PAO) base stock to a Group III hydro-isomerized (VHVI) petroleum base stock.

However, Castrol continued to label SYNTEC as “synthetic” oil. Castrol’s reasoning was that this extremely hydro-processed, multiple-refined Group III VHVI petroleum oil now performed almost exactly like the Group IV PAO synthetic oil. And, in fact, Castrol was right. The performance of petroleum oil after this advanced processing nearly matched synthetic oil.

Mobil, the world’s leader in synthetic motor oil, cried foul. Performance aside, SYNTEC was not a PAO-based synthetic oil, period. Mobil said Castrol should not be able to use the term “synthetic.”

For its part, in 1998, the Society of Automotive Engineers (SAE) backed away from the controversy between Big Oil and Big Chemicals. They simply deleted all references to “synthetic” in their documents. The SAE had previously documented that “synthetic base stocks must be Poly-Alpha-Olefines (API Group IV).

Marketing Trumps Chemistry

In 1999, the National Advertising Division of the Better Business Bureau took the side of Castrol. The BBB-NAD arbitrates conflicting claims made by advertisers and essentially decides what is false, misleading or deceptive advertising—and what is not. Its ruling was that “synthetic” is a marketing term and not a description of the chemical composition.

Instead of a narrow definition of building big molecules from small ones, which was Mobil’s position, the BBB-NAD ruling went with the wider definition of “the product of an intended chemical reaction,” which was Castrol’s position.

So, technically, the term “synthetic” does not mean what it once did. The term “synthetic” has become something of a marketing and advertising term! Caveat Emptor (“Let the buyer beware”). Group III VHVI petroleum-based oil is now commonly called “synthetic” in North America. Germany and Japan sill restrict the use of the term “synthetic” to Group IV PAO-based oil, the original synthetic.

Group III VHVI petroleum-based oil costs just half as much to produce as Group IV PAO-based (synthetic) oil. The VHVI oils, labeled as synthetic, were lower priced and took a lot of the high-end, high-performance oil market away from the “true” PAO-based synthetic oils. A decade after the ruling, virtually the entire synthetic oil market has switched from using PAO base stock to VHVI petroleum base stock—still labeled “synthetic.”

Mobil also went the VHVI route for its synthetic oil. The product now labeled as “Mobil 1 Synthetic Motor Oil” is VHVI petroleum-based oil. The product now labeled as “Mobil 1 Extended Performance Synthetic Motor Oil” is also a VHVI petroleum-based oil but with 50 percent more SuperSyn (PAO-based original synthetic) than Mobil 1.

Semi-Synthetic & Synthetic Blends

So, if “synthetic” oil is made up of Group III VHVI and Group IV PAO oils, what is “semi-synthetic” oil? Semi-synthetic and synthetic blends are made from Group II conventional petroleum oil and Group III VHVI petroleum oil. As a general rule, semi-synthetic oils, or synthetic blends, are 70 percent petroleum oil and 30 percent VHVI petroleum oil.

With just 30 percent VHVI oil, it is easy to see why semi-synthetic oils perform only a little better than conventional petroleum oils. And yes, they cost 30 percent more, but they typically boost the oil change interval from 6,000 miles to 7,500 miles, which is about 30 percent.

Oil Analysis Required

All these changes in chemistry mean one thing for police fleets. You must perform an oil analysis to know when to change semi-synthetic or fully synthetic oils! To save money on operating costs, you must extend oil change intervals. However, you are completely on your own in deciding how many miles between changes.

The oil analysis will cut through the semantics of fully synthetic, synthetic, semi-synthetic, synthetic blend, the PAO/VHVI ratio, the Group II/Group III ratio, etc. What do you care what the oil is called? You just want the lowest cost engine protection for your police vehicles, and the oil analysis is the only way to do this.

Heads-up on the oil analysis: The lab providing the results will give you a lot of numbers with units of measure you have never heard of, may or may not tell you the acceptable range for those various numbers, and, in fact, may not even understand what you are asking for.

Keys to Oil Life

A few of the deciding factors in evaluating oil life are oxidation, total base number and viscosity. These three are also interdependent. As the oxidation number increases, the total base number (TBN) decreases and the viscosity increases. A standard oil analysis may provide other information, but these three are important to determine the remaining life of the oil.

The Viscosity Index test is a measure of how much the viscosity (thickness) is affected by temperature. The higher the Viscosity Index, the less the oil thickens as it gets cold and the less it thins out as it gets hot. The culprit is a form of wax. Advanced dewaxing technology is essentially what turns a Group II petroleum base stock into a Group III petroleum that can be called synthetic. In fact, these Group III VHVI petroleum oils rival Group IV PAO synthetic oils.

The Oxidation Stability test is a measure of the resistance of the oil to oxidize. Better oxidation stability means less engine deposits and sludge. Better oxidation stability also means the oil resists thickening, so it gives the wear lubrication and fuel economy (less friction) appropriate for the labeled viscosity of the oil. All synthetic oils are superior to conventional petroleum oil in oxidation stability.

The test for Total Base Number measures the ability of the oil to resist the formation of acid from the by-products of combustion. The TBN is a measure of how much alkalinity (base) the oil has in reserve. Bases neutralize acids. The strong acids in the oil attack the piston rings and cylinder walls. The weak acids in the oil attack the lead-based bearings.

Sulfuric, nitric and hydrochloric acids also attack the additives added to the oil. In most cases, the additives are destroyed long before the base oil stock’s (petroleum or synthetic) ability to lubricate the moving parts. An oil with a high TBN, a high reserve to cancel acidity, will reduce the engine wear (rings, bearings) caused by acid. All synthetic oils have higher TBN values than conventional petroleum oil.
Simple Yes or No

After presenting the results of the analysis, be sure the lab answers this “yes-or-no” question: Does this oil, with this mileage, in this type of service, need to be changed? Yes or no? If you get a “No, it still has life in it” answer on 10,000-mile oil, try again at 12,500 miles, then 15,000 miles. Even with the best full-synthetic oil, it is unlikely the change interval will exceed 15,000 miles. The base oil itself might still be fine, but the additive package (anti-foam, anti-oxidizers) will probably be used up.

Extending oil changes will lower maintenance costs. During an early 2011 price check, PAO-based and VHVI-based full-synthetic oil ran from about $5.99 a quart to $8.79 a quart for an average of $7.65 a quart. Valvoline SynPower and Lucas Oil Synthetic were on the low end of the range. Mobil 1 was mid-range. Mobil 1 Extended Performance and Amsoil Signature Synthetic were on the high end of the range.

Police Fleet Manager asked a Midwest sheriff’s department to test synthetic oil in its fleet of V6 Chargers. They selected one of the less expensive, full-synthetic oils. After the oil analysis at 10,000 miles, the oil company’s lab said the oil should have been changed at 9,000 miles. And that is the lesson for fleets. You must perform an oil analysis. If you can’t extend the oil change interval, operating costs probably won’t be lowered. This particular fleet made the decision to use a higher end, full-synthetic oil for its goal of 12,000-mile oil change intervals.

Based on 30,000 miles per year and oil change intervals of 6,000 miles for petroleum oil and 12,000 miles for full-synthetic oil that actually reaches 12,000 miles, along with shop rates of $85 per hour and 30 minutes per change, the operating costs can be lowered. With figures based on the cost of Mobil 1, the savings are about $110 per car, per year.

The real savings in all of this is in the cost of labor for the oil change due to fewer labor charges. That is, the greater number of miles is offset by the higher material cost of the synthetic oil. If, somehow, the oil is changed at no charge, there is practically no savings.

Extended oil change intervals aside, should all police vehicles use synthetic oil or semi-synthetic oil? Yes. Synthetic oil is significantly better than petroleum oil in the exact areas that police vehicles are used differently from retail vehicles. These include excessive idling and high-temperature/high-engine rpm driving (wide open throttle). Better engine protection during cold starts (first start of the day) and during extremely cold weather is just a bonus.


Full-Synthetic Oil and Semi-Synthetic Blends (Group III VHVI, Group IV PAO) have definite advantages over conventional petroleum oil (Group II) in police use.

Better low temperature viscosity (less thickening)
Better high temperature viscosity (less thinning)
Better shear stability (less molecule breakdown)
Less evaporative loss at high temperatures
Better resistance to oxidation, thermal breakdown
Less oil sludge
Better fuel economy (less engine friction)
Easier cranking, faster engine starts (extreme cold)
Better lubrication on cold starts (less engine wear)
Better flow in extremely cold conditions
Extended oil change intervals

Published in Police Fleet Manager, Mar/Apr 2011

Rating : 6.7


Comment on This Article

Synthetic oil

By Denny Kincade

In addition to the cost of the samples mentioned by Floyd, where do you get oil filters that perform like they should up to 15,000 miles. So add the cost of samples to changing the filter between oil changes is there really enough savings to justify? We use petroleum based oil every 5,000 miles and when they are disposed of at 100-130,000 miles we do not have an oil consumption problem nor do we lose engines. Maybe your drivers are easy on their cars but when ours come in every 5,000 miles we find tires and brakes that need attention to keep them safe.

Submitted Jul 18 at 1:26 PM

Shop supervisor

By Floyd

your claim you saved 110.00 a car, does that incluide the cost of oil samples. Second a 30 minute oil and filter change,no further inspection of the vehicle or is that done at another interval? dosnt seem to add up??

Submitted May 18 at 3:37 PM

Synthetic Confussion

By Gary Lykins

Thanks PFM I feel like I can, at long last, give an educated answer to questions about the synthetic nomenclature.

Submitted May 17 at 9:59 AM

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