The $2,000 per month he paid in the late 1990s had gone to $7,900 in 2001, then $8,600 the following year, he said. Now, the company wanted $11,710. And that didn't include other monthly fees he was obliged to pay for credit card processing and station maintenance.

Today, many dealers say the oil industry bonanza of 2005 is passing them by. Their parent corporations have posted record profits -- $9.9 billion during the three months that ended in September in Exxon Mobil's case -- from prices that briefly topped $70 for a barrel of crude and $3 for a gallon of gas.

But ask dealers about their profit margins, and some insist they're making 2 cents or less per gallon. They may even be losing money selling gas.

To understand why, you have to peer into the murky mechanics of street-level gasoline pricing. Dealers compete against each other while paying a host of fees to their parent companies. Government demands its own cut, through taxes and permit fees.

First, understand that not all stations operate the same way. Some sell gasoline for the oil industry's big brands, such as BP, Chevron or Shell. Others don't, offering what amounts to generic gas.

Even among the brand-name stations, there are important differences. Many stations are run by dealers who essentially act as franchisees, leasing their facilities from the company and setting their own retail prices. Others are run directly by the companies with a manager who oversees several stations.

The large oil companies can set prices as high or low as they want at the stations they directly control. But they can't dictate retail prices to the franchisees. As far as the oil companies are concerned, those dealers are free to run their businesses as they choose.

"Shell operators are independent businesspeople who make their own operating decisions and have the right to set gasoline prices as they believe appropriate," Shell spokeswoman Karyn Leonardi-Cattolica said.

But those dealers don't have complete freedom. Fees and requirements imposed by their parent companies greatly influence the prices they charge.

"The law says (oil companies) can't tell us how to price, and they don't," said Bill Currie, a Chevron dealer in San Francisco. "But they'll price wholesale in ways to force you up and down."

Dealers at big-brand stations, for example, typically must buy their gasoline from the company they represent, even if they could find less-expensive gas elsewhere.

And the amount each oil company charges dealers for wholesale gasoline varies from one location to another, in a system called "zone pricing." A dealer in San Francisco's Marina district might not pay the same price, for the same gas, as a Mission District dealer working for the same firm. Dealers resent that.

"Zone pricing is nothing less than redlining in the insurance industry," said Dennis DeCota, executive director of the California Service Station and Automotive Repair Association.

Dealers also typically pay a monthly fee, determined by their company, for processing credit card transactions. They pay another for maintenance on the station's equipment, sometimes whether they need repairs or not.

Tan's experience with rapidly rising rent is hardly unique. As land prices soared throughout California during the past five years, many oil companies ratcheted up rental fees to levels the dealers say they can barely afford. The companies say the higher rents merely reflect the market.

"The current rent structure is based on the appraised value of the real estate, improvements and equipment using standard commercial real estate techniques," Leonardi-Cattolica said. "To the extent that rents went up, it was to bring them in line with the rest of the market."

The dealer charges $2.499 for a gallon of regular. Of that, 13 cents go to his rent, property taxes and monthly maintenance fee, combined. Credit card processing fees eat up more than 5 cents per gallon. Other taxes -- including federal, state and sales -- consume a little more than 57 cents. And he pays his brand-name oil company about $1.83 for each gallon of wholesale gasoline.

The result -- he's losing about 8 cents on every gallon of regular. And that's before he factors in his payroll, his workers' compensation insurance and the other myriad costs that go into running a small business.

Other local dealers, who also requested anonymity, reported similar costs, although the wholesale gasoline price varied by as much as 11 cents. Those losing money on gas have to find some other way to turn a profit, such as washing cars or selling Slurpees.

"You would think if they owned everything, they could control the price the way they want it, and that's what they don't have right now," Currie said. "The companies are just kicking our butt, and they can do it."

A spokesman for San Ramon's Chevron Corp., which makes the brand Currie sells, said the number of Chevron-owned stations has actually decreased in recent years, as a result of investment decisions.

"It is regrettable that certain dealers may find it difficult to compete in today's marketplace, but this is no evidence that Shell has acted improperly," she said.

One, however, succeeded. A Boston jury last year found that Shell used unfair tactics against some of its Massachusetts dealers. That decision has been appealed.

Tan has also gone back into the business, buying a Chevron station in Berkeley. His new company, he said, has treated him well, even though profits still aren't high.

"I've got friends who come here from the Philippines and say, 'You must be a millionaire,' " Tan said. "You don't make much money from gasoline."

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