Third-generation Prius resolves bladder issue

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When the next-generation Toyota Prius hits dealer showrooms in late May, it will come with a bigger engine, improved fuel economy and solar-powered cabin cooling.

What it won’t have is the innovative ‘fuel bladder’ that has served as the gas tank for the Japanese-built hybrid.

Toyota decided to ditch the bladder in part because some Prius owners complained that it held less fuel than the 11.9-gallon capacity claimed in the car’s owners manual — potentially taking a big bite out of the car’s range between fill-ups.

The new 2010 Prius — the third-generation of the groundbreaking gas-electric hybrid — will use a rigid tank made of a lightweight resin rather than the collapsible bladder.

‘The chief reason was because one of the sore points with the current-generation Prius was the ability to fill up the fuel tank and the accuracy of the fuel gauge,’ said Bill Kwong, a spokesman for the automaker.

The change is coming too late for Darlene Sharar, an engineering technician who lives in rural Washington and often drives in areas where gas stations are few are far between.

‘In any other car I’ve owned, I know a tank of gas will get me ‘X’ number of miles,’ Sharar said, adding that she often could pump no more than seven gallons of gas into her 2008 Prius even when the fuel gauge was flashing ‘empty.’

‘Instead of a range of 500 miles, I’ve got a range of 300 miles,’ she said. (The Prius gets 46 miles per gallon in combined city-highway driving, according to government figures.)

Attempts to get Toyota to fix the problem were unsuccessful, she said. In an e-mail to Sharar, a Toyota customer service representative said the issue involves ‘the design of the fuel tank and there is no repair available to change the design.’

Sharar eventually traded the Prius in on a new 2009 Toyota Camry.

The automaker blames the problem in part on temperature changes. The Prius owners manual notes that the capacity of the fuel bladder drops by about 1.3 gallons at 14 degrees Fahrenheit. Maintenance manuals, meanwhile, note that the problem often can be solved by recalibrating the fuel gauge.

Kwong said that owners complaining of a bladder problem usually say the tank won’t take more than 9 1/2 or 10 gallons of fuel.

‘I’ve never heard of only being able to get seven gallons’ into the bladder, as Sharar contends, Kwong said.

Over the years, the National Highway Traffic Safety Administration has gotten a dozen or so complaints from consumers about the Prius’ fuel-tank capacity or the accuracy of its gas gauge, which can be a related issue. The agency hasn’t formally investigated the complaints.

Fuel bladders, common in airplanes and racing vehicles, are a rarity in commercial passenger cars, which typically use rigid tanks made of high-density plastic, said Craig Hoff, a professor of mechanical engineering at Kettering University in Flint, Mich. By collapsing as fuel is pumped to the engine, bladders help prevent fuel vapor from building up in the tank, thereby reducing hydrocarbon emissions.

The Prius’ new fuel tank will use an improved vapor-recovery system that will allow the car to retain its low-emissions rating from California regulators, Kwong said.

—Martin Zimmerman