Remember when the offer of a bigger rental car was good news? Yesterday’s upgrade is now considered a downgrade. Priceline.com found that 72 percent of 764 customers surveyed last year wanted more environmentally friendly vehicles—and that was when the price of gas averaged less than $3 a gallon. A Hertz spokeswoman cites a 40 percent increase in customer requests for hybrid rentals and other fuel-efficient cars this year.

But there might not be enough to go around. At Hertz, hybrids make up 0.01 percent of the domestic fleet; Avis and its sister company Budget, 0.008 percent. Budget rents hybrids at about 115 of its 918 U.S. sites; Hertz, mainly at the nation’s 50 busiest airports; and Avis, in nine areas outside California, where hybrid rental cars are most likely to be available.

We tried to book a hybrid vehicle in Los Angeles through six agencies. For a three-day rental three days in advance, only Alamo, Hertz, and National had a hybrid rental. For a booking two months ahead, those three and Avis had a hybrid. Budget was sold out in both cases, and an Enterprise agent told us hybrids can be requested but not guaranteed. Calling sometimes proved more effective than booking online.

Some agencies lump hybrids into categories such as Cool Cars (Avis), Driver’s Choice (Budget), or Green Collection (Hertz) and charge a premium, which gas savings might not offset. At Avis, our Altima had a base rate of $253 for three days, compared with $111 for a full-sized Chevy Impala. The charge for a three-day hybrid rental including taxes and fees: National’s $169 bested Alamo’s $189, Hertz’s $196, and Avis’ $321.

Bottom line
Agencies say they’re adding fuel-efficient cars. Meanwhile: