The bad news: Renting a car requires gasoline. The good news: Rental costs drop dramatically in autumn. Better news: One rental company offers free gas.

There are catches, however, to every rental out there, so read on.

Despite the hassles, renting a car to leave the city may still be an affordable and worthwhile way to reach places not serviced by public transportation. Nonetheless, now that formerly mundane expenditures have become luxury goods, it’s important to find the right car, which takes some time and tenacity.

Because of stringent state liability laws that make owning a car-rental or -leasing business incredibly onerous, the supply of rental cars in New York City is uncommonly low, given the demand. Courtesy of a provision buried in the $286.4 billion federal transportation bill that passed the House this summer, however, those laws may soon change, making it easier to own a rental or leasing company in New York. The new law, if it passes the Senate, would prohibit states from holding owners of motor vehicle-rental and -leasing companies liable for accidents involving their vehicles, provided there is no negligence or criminal wrongdoing on the owner’s part. Eventually, those savings will be passed on to the consumer.

The new legal climate has not yet produced a glut of cars, so for anyone wanting to leave the city to catch some fall foliage, the watchword remains shop around.

“Car companies make a lot of pricing adjustments multiple times a day to move cars,” the director of air and car at Travelocity, Jeff Varhol, said. “It behooves you to shop around.”

There is comparison shopping on the Web at sites such as CarRentals.com and RentalCars.com, where the question is usually, “to rent at an airport or not to rent at an airport?”

Despite the deep discounts on car rentals offered to people who purchase airline tickets, for those stuck on the ground, renting a car at an airport is generally a more expensive option, due to higher taxes. That new convention center or stadium? It’s often paid for by higher rental car taxes, a cost passed on to visitors so voters never feel the pinch.

To make things complicated, however, New York is one of the only cities where rental car taxes at airports are .1% cheaper than those at local outlets, meaning the price to rent is generally the same.

In New Jersey, the airport tax is twice the rate found at local rental retailers. Yet renting a car at Newark Airport is nonetheless cheaper, in general, than anywhere in New York City, especially if you take advantage of the deals onTravelocity.com. That price, of course, does not include the cost of getting to Newark.

Mom-and-pop shops struggling to compete with the corporate giants offer surprisingly good incentives. At Image Rent a Car in Crown Heights, Brooklyn, the owner, Sam Zilberman, said he offers to pick up customers and bring them to his rental agency. He also drops luxury car rentals at your doorstep: If nothing else, you’ll look good when that $1,200-a-day, $180,000 Bentley GT Continental rolls up to your six-floor walkup.

For the more economical-minded renter, Mr. Zilberman suggests groups of up to seven people rent a minivan, which goes these days for about $75 a day during the week and $85 on weekends in the city. In New Jersey, the cheap minivans rent for about $50 during the week and $80 on the weekend.

Volatile gas prices, which have risen almost $1 nationally in the past year, have some companies poised to increase their rates. Cendant Car Rental group, comprising Avis and Budget companies, has plans to raise prices 5%. Enterprise, which boasts the nation’s largest car rental fleet, has cut prices on the weekend by 50% in some markets. The bargain is a gift to customers wary of renting in an inflationary oil market, the group’s vice president in the New York area, Andy Church, said.

Here’s the kicker: That deal, like so many that flood the market on a daily basis, does not apply to Enterprise outlets in New York City.

Perhaps the brightest option on the horizon is the Zip Car, an ideal choice for those not going far from the city, renting more than a once a year, or wanting a car for occasional runs to the supermarket. Given that gas in New York City is nearing European dimensions – reaching a peak in recent weeks of nearly $4 in some neighborhoods – Zip Car’s policy to provide free gas may seem foolhardy. But it’s true: There’s an unlimited gas card usable at major gas stations in the glove compartment of every car.

You do pay for the gas somewhere. To rent a Zip Car, you need a membership that includes a $25 application fee, $50 annual membership fee, and a $100 deposit (refunded whenever you end your membership). These upfront costs offer a sharp contrast to the hidden costs of renting a car, such as insurance, which runs about $20 a day, and the rising price of gas, the regional vice president of Zip Car, Julian Espiritu, said. He spent 20 years working for Budget Rent a Car.

Zip Car is decidedly not a rental car company, and it balks at the designation. Its organizing principle is to give people in cities the occasional use of a car without the hassles of alternate side parking, insurance, and car alarms. Rather than have a car sit idle in a parking lot or driveway – as it does 90% of the time, according to the San Francisco-based City Car Share – as many as 50 people can collectively share one car among them.

This means bottlenecks can occur when a car is rented to one person for an extended period of time. “We discourage using it as a [long-term] rental,” Mr. Espiritu said. “It’s really an alternative to car ownership. Once that car is out of the system for an entire week, the system gets bogged down.”

Still, for short trips outside the city, Zip Car may be an economical alternative to renting, especially for weekend use. The cheapest Zip Cars – the Volkswagen Beetle and Jetta – cost $65 a day. A typical rental agent charges $69 to rent the tissue box of a car known as the Hyundai Accent for the same period of time. As usual, rentals Monday through Thursday are significantly cheaper, with rates of $41 typical in autumn New York. In New Jersey, weekend rates are even better, with an economy car costing about $50 (not including gas and insurance). Better deals can be had from rental agencies for weeklong use.

Zip Car offers 67 cars parked in garages in Manhattan, 13 in Brooklyn, and one in Queens, varying from the prosaic Volkswagens to the BMWs and Mini Coopers at the pricier end of the spectrum. Specialty cars include the Toyota Prius hybrid and a two-wheel drive, four-cylinder Ford Escape.

Like other rental companies, Zip Car lowers its rates after the summer. That means more cars are now priced at the $65 level, and they’ll stay that way through fall and winter unless gas prices continue to skyrocket, Mr. Espiritu said.

The point at which Zip Car becomes expensive is when your trip odometer hits 125 miles. After that, each additional mile costs 18 cents. A smart way to extend your mileage is to take the MetroNorth Railroad to the Beacon, Tarrytown, North White Plains, or Woodlawn stations. Zip Cars are parked there, giving you traffic-free driving and extra miles for the price of a railroad ticket.