Gasoline Blending Glitch May Have Cut Octane

Customers who bought premium gasoline from Los Angeles-area Mobil stations in recent months may have gotten a little less oomph in their tanks than usual.

Government inspectors are investigating possible glitches in the mixing of ethanol with gasoline at Exxon Mobil Corp.’s terminal in Vernon. Fuel experts say octane levels in high-test fuel distributed from the terminal could have been degraded, although probably not enough to take the gas below the 91-octane minimum for premium.

The episode illustrates the complexities and the potential for problems as California refiners and distributors switch to ethanol from the additive MTBE as a smog-reducing agent. MTBE, which pollutes groundwater, will be banned from California gas next year.

Last month, for example, a miscue resulted in ethanol being left out entirely from 420,000 gallons of regular gasoline distributed from Arco’s terminal in San Diego. The company had to retrieve the fuel from 59 stations and re-blend it, leaving some stations without regular gas for a few days.

By all accounts, the Mobil case wasn’t as severe. The investigation began in early April, when two Mobil dealers complained that they were shorted on tanks of fuel from the Vernon terminal, said Jeff Humphreys, deputy director of the Los Angeles County Office of Weights and Measures.

Inspectors conducted tests and then shut down three of the terminal’s 12 gasoline-dispensing systems because they gave out significantly less fuel than indicated by the meters, Humphreys said.

Humphreys said his agency was looking into the possibility that the pumps that add ethanol malfunctioned, putting less ethanol into the mix and lowering the total volume of the fuel that ended up in the delivery trucks. That would reduce octane levels, industry experts said, because ethanol acts as an octane booster in addition to helping create cleaner-burning fuel.

A person familiar with the situation said trucks drove away light by 150 to 200 gallons, or up to 2% short for a typical 9,000-gallon tanker load. The person added that the blame probably rests with the ethanol nozzles and that the problem dates back to the beginning of the year, when Vernon’s bays were retrofitted to dispense ethanol.

California rules require gasoline blends to contain 5.7% ethanol by volume. If an entire volume deficit consists of missing ethanol, the person said, “that calls into question the integrity of the blend and the octane rating.”

Exxon Mobil spokeswoman Carolin Keith confirmed that there were faulty meters that reduced the volume of gasoline pumped into the delivery trucks. She said the meters were being repaired and that affected Mobil dealers would be compensated.

But Keith said there was no evidence of any problem with the ethanol mix or with octane levels.

The company has more than 560 Mobil stations in California, most of them in Southern California, Keith said. The Vernon facility is Exxon Mobil’s largest fuel terminal in the state, each week shipping out about 1,000 truckloads of gasoline -- or 9 million gallons -- to about 300 area stations.

A gasoline-blending expert said the Vernon situation probably had only a small effect on octane levels.

If there was a 200-gallon shortage per tanker-truck and the missing volume was entirely ethanol, the blend probably would have dropped to 3.5% or 4% ethanol from the required 5.7%, said Bob Reynolds, president of Downstream Alternatives, a South Bend, Ind., consulting firm that specializes in ethanol fuel recipes.

With that lowered amount of ethanol, Reynolds said, the fuel’s octane level probably would drop only about three-tenths of 1 octane point.

He calculated that Mobil’s normal blend for premium gas would carry octane of about 92.2 and would be above the 91 posted octane even with the botched ethanol injection.

“There might be a violation there from the standpoint of the amount of ethanol, but unless they were right at the edge to start with, there wouldn’t be an octane problem,” Reynolds said.

Automobile experts say the octane reduction probably would be too small for consumers to notice.

Exxon Mobil’s Keith said she couldn’t vouch for Reynolds’ calculations. She said that typically, the gasoline used to make premium arrives at the fuel terminals with 89.5 octane and that the ethanol infusion adds up to 2 more points.

Based on Reynolds’ calculations, a three-tenths reduction under that scenario still would keep the premium gas above the posted 91 octane level.

The state Division of Measurement Standards, which is assisting in the Vernon terminal probe, is responsible for enforcing octane levels. The agency is prepared to conduct an investigation if evidence arises that the Exxon Mobil octane fell below minimum levels, spokesman Jay Van Rein said.

The California Air Resources Board, which is responsible for fuel emission standards, also inspected the Vernon terminal and found no problems in that regard, spokesman Rich Varenchik said.

But Keith said the CARB inspectors tested only fuel coming from the working nozzles, not from the ones shut down by the county.

“Without CARB testing the nozzles that were shut, we can’t determine whether there was an issue with the octane or ethanol blending,” Keith said.

Varenchik couldn’t say Monday why the closed nozzles weren’t tested.

The switch to ethanol from MTBE is well underway in advance of the Jan. 1 ban. Though ethanol is considered an environmentally sounder alternative, it creates a bigger headache for oil companies.

Ethanol can’t be carried in multi-fuel pipelines, such as those in California, and therefore has to be added to gasoline at fuel terminals instead of at refineries, where MTBE was added.

That has forced oil firms to reconfigure existing terminals to accommodate tanks for storing pure ethanol and blending equipment and meters to inject the right amount of ethanol into various grades of gasoline.

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Times staff writer John O’Dell contributed to this report.

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Gasoline octane ratings

Octane is a gasoline component produced during the refining process that keeps compressed gasoline from self-igniting prematurely, which can cause the engine to knock or rattle.

* Octane ratings reflect the percentage of octane or combustion-resistant material in gasoline, so 87-octane gas is 87% octane and 13% other components or is a mixture of other compounds, such as MTBE or ethanol, that have the same effect.

* Octane ratings show how much the gasoline can be compressed before it ignites by itself and thus what resistance the fuel has to keep the engine from knocking.

* The American Petroleum Institute recommends drivers try different grades of gasoline and decide which works best with their car.

MOST COMMON GASOLINE OCTANE RATINGS*

Regular -- 87

Mid-grade - 89

Premium - 91

*Vary by state.

Sources: Federal Trade Commission, Chevron, “How Stuff Works”