The car rental giant Hertz, the maker of popular fuel-efficient cars such as the Ford Focus and the Toyota Prius, has found that customers are generally unhappy with the service, with many complaining about fuel-efficiency upgrades being a drain on their wallets and car expenses.

In a report titled “Fuel Impairment Is The Biggest Risks to the Vehicle,” Hertz said fuel-inflation rates are the biggest threat to the brand’s long-term viability.

Fuel inflation is a common problem in the U.K., which recently introduced a fuel-insurance program to help drivers cut costs and help offset rising fuel costs.

Fuel costs have risen rapidly in recent years as people use fuel-saving technologies such as electric cars, but the cost of gas has remained stable.

Hertz said the most expensive fuel-purchase program it has ever implemented has cost the company $25 million.

It said the program, known as Fuel-incentive Rebate (FIRE), helps owners save money on their fuel bills by reducing fuel consumption.

Hertz says the average rebate program costs $1,200 per customer.

But some customers are saying that many of the savings they are getting from the program are going toward fuel expenses, with some complaining that they are going to pay more for their vehicles.

The company said customers who choose to participate in the program will receive a monthly rebate of $15, which is $5 more than the company would pay if they paid monthly for the fuel-price increases.

The program has been criticized for its price increases, which have led to some owners canceling their leases and many others getting out of the program.

A spokeswoman for Hertz told The Wall St. Journal that customers who have signed up to the program have been charged an average of $1.50 per month for fuel and $2.30 for repairs.

But the company said the average annual price for a typical customer is $4,719.

Herts spokeswoman Kristina Dzodan told The Journal that Hertz has reduced the number of lease renewals that are cancelled, as well as other fees that have been levied on customers.

The spokeswoman said the company is working to make the program more efficient and to increase incentives for people to renew their leases.

The problem, Hertz added, is that the new program doesn’t have a cap on how much fuel you can use per month.

The average fuel-use rate has been increasing since 2009, when fuel prices were higher, according to a Hertz spokesperson.

Dzodan said the new rebate program is part of Hertz’s strategy to get people to pay less for their fuel, and it will continue to work in areas where there are significant fuel-consumption challenges, such as in places like urban areas where demand is highest.

She added that the company believes its incentives are effective at reducing fuel costs, but that there is more work to be done.

Hannibal Buzsperger, president of the American Automobile Association, which represents more than 2,000 auto dealerships, said the fuel rebate program makes sense for the market, but it is a bad idea for consumers.

Buz told CNBC’s Squawk Box that the rebate is the wrong way to help consumers save money and he said it will hurt small and midsize businesses that are struggling to keep up with demand.

Buosperger added that people are looking for cheaper fuel to make up for the costs of their cars.

Hewlett-Packard Co. has been one of the largest car companies to offer a fuel subsidy program since it began in 2003.

The company has received praise from the public for its effort to reduce its carbon footprint, which has helped reduce emissions by more than 80 percent since 2000.

The new program, however, is another example of companies using incentives to make fuel-economy improvements.

In June, Ford announced a plan to provide $100 billion in incentives over the next decade to encourage people to use fewer fuel-intensive vehicles.

The program would allow companies to sell more fuel- efficient vehicles.

Ford said it is also introducing a new car that it says is fuel-independent, which could help reduce its fuel-costs.