There was a time when most rental car customers would have welcomed an upgrade to a midsize or sedan, a minivan or an SUV, but that was before gas was "upgraded" to $4 a gallon or more.
Now some customers say rental car companies increasingly try to pressure them to take the gas-guzzling bigger vehicles, even when they have reserved a compact. Car rental agencies apparently can't keep enough of the smaller, more fuel-efficient cars on lots to meet demand.
Aileen Goldstein, a marketer and frequent traveler, said she encountered pushy rental car customer service representatives on a recent trip to a trade show in Phoenix. They have "gotten a little harder" with their upgrade offers, she said.
"I try and watch whatever we spend," Goldstein said. "I still didn't know how much gas cost in Phoenix. I certainly didn't want a big gas-guzzler going short distances, and I didn't want to pay $80 when I could pay $40 to fill up a tank."
"They're lucky that people are renting cars in general," she added.
In response to skyrocketing gas costs, some frequent renters have updated their online rental profiles to say "No minivan or SUV." Others have waited in lengthy lines at customer service desks, enduring arguments with service representatives to switch to a compact car, they say.
However, industry insiders say the link between rental car customer service and rising gas prices is not completely clear.
To entice customers to take the bigger vehicles, renters say they have seen some rental car companies drop the prices of SUVs and large cars.
"It's kind of ironic, because usually the small cars are the cheapest," said frequent business traveler Michael Capel. "If the SUVs are sitting on the lots of the rental companies, they'll have to discount them."
Chris Brown, managing editor of Auto Rental News, called the increase in rates for compact and economy cars a "supply and demand issue."
He said, "It filters out to every other part of the auto industry. This is the environment we're living in right now — this is the reality we're living in right now."
A spokeswoman for Enterprise Rent-A-Car — the largest rental car company in North America, which also includes the National and Alamo brands — said her company has not lowered rates for SUVs and trucks.
"Overall, it has not been a strategy for us to lower prices on SUVs and trucks in an effort to rent them, as our customers still request and need them," Laura Bryant told ABC News in an e-mail.
Bryant said that while there is an increase in demand for smaller cars Enterprise's largest increase has been for full-size vehicles.
"Also, consider that, previously, people used to reserve an economy car, but actually hoped to luck out and get an upgrade — and that may not be happening as much anymore," Bryant said in her e-mail.
Brown said the situation with rental cars is a symptom of larger auto industry trends.
"This is a painful market adjustment that's happening," Brown said. "It starts with the major manufacturers, and the car rental industry is trying to accommodate that."
Brown defended national rental car chains, saying the companies' chief concern is superior customer service.
"They basically want to satisfy the customer," Brown said. "Customer service is extremely important to these car rental companies. At the end of the day, these cars are a commodity and how are they doing to differentiate themselves from other car rental companies is in customer service."
If renters have a reservation and are concerned about being stuck with a larger-than-wanted vehicle they should "call over there and say, 'I want the small car, and if you don't have the small car I'm taking my business elsewhere,'" Brown said.
Daniel Lemin, who travels frequently for his work as a professional photographer, recently reserved a compact car from Dollar Rent A Car in Los Angeles. He said representatives tried to "upgrade" his rental car to a minivan when he arrived.
The employees "were pretty aggressive about it because they were out of cars," he said. But "I didn't want to be faced with a $60 or more gas bill."
Lemin said he has seen the daily rental prices of SUVs and minivans decrease over the past four to five months to the point where the cars are less expensive to rent than any other vehicle available.
An Internet search by ABC News this week found Budget Rent A Car offering a daily rental of an "intermediate SUV" from Newark airport in New Jersey for $66. An economy vehicle was $76, and a compact car cost $77.
Some rental car companies do allow customers to reserve fuel-efficient or hybrid cars but those options are limited and often cost substantially more.
"There are times I've tried to rent a hybrid, and they're so ridiculously expensive at any of the rental places. I think that sort of indicates the level of demand," Lemin said.
Last week, business traveler Kumar Lakhavani booked a compact car for his stay in Washington, D.C., but when he arrived, the company was out of compacts. He was offered a larger car and refused to take it.
"I said, 'No, I'm just one person,'" Lakhavani said.
The change in rental car service is particularly stressful for frequent business travelers, some of whom must fund fuel costs themselves, he said.
"If you do a lot of driving, that ends up costing a lot of money, and apparently car rental companies don't care anymore," Lakhavani said. "About two years ago, if I had asked for an upgrade to a small SUV, it would have cost me $5 to $6 a day extra."
To increase the likelihood of getting the rental car you want — whether it's a compact or an SUV — Brian Ek, the general manager of Priceline.com's PriceBreakers travel service, suggested booking reservations as far in advance as possible.
To improve a rental car's fuel mileage, Ek said drivers should avoid sudden starts and stops, check the car's tire pressure "first thing," leave windows up and turn on the air conditioning.
"The easier you can be on your pedal the better your mileage can be," he said. "You'd be surprised — every little bit helps."
Lakhavani said rental car companies need to change their marketing strategies to fulfill a new kind of consumer demand.
"Our auto industry was for a long time in denial," he said. "They need to anticipate what's coming. If Avis came up tomorrow and said, 'Our vehicles are fuel-efficient vehicles,' they'd see a surge in people wanting to rent from Avis."