WASHINGTON A group of Democratic Congressmen has asked the National Conference on Weights and Measures to address the issue of the impact of summer temperatures on the volume of gasoline and diesel delivered to fuel buyers by retail outlets.

And, in a related development, a leading California fuel retailer has announced it plans to alert consumers that temperature can affect the amount of energy they receive when pumping fuel.

A spokeswoman for Tesoro Corp. said the company plans to put decals on its retail fuel pumps in California stating that, based on temperature, the amount of energy in a gallon of fuel can vary.

The decals will state: 'This pump dispenses motor fuel by volume measured in standard gallons (231 cubic inches), as certified by the California Division of Measurement Standards, without adjusting for possible variations due to temperature or other factors which may affect the energy content of each standard gallon dispensed.'

'Tesoro did make a business decision to apply decals on our pumps in California,' spokeswoman Sarah Phipps told a trucking publication. 'However, we want to make it clear that we are squarely aligned with the industry on there being no merit to the hot fuels claims.'

'Hot fuel" refers to gasoline and diesel fuel sold by retailers at temperatures above the national standard of 60 degrees.

Last month, the first Congressional hearings on hot fuel were conducted in California. Some of the House members who were at the hearing and two senators all Democrats sent a letter to the chairman of the national weights and measures trade organization.

'As you are aware, a recent report conducted by subcommittee staff indicates that this practice will cost the American consumer an estimated $1.5 billion in the summer of 2007 alone,' wrote Rep. Dennis Kucinich, D-Ohio, chairman of the subcommittee on domestic policy of the House Committee of Oversight and Government Affairs.

The letter was sent to Michael Cleary, chairman of the National Conference on Weights and Measures.

One of the missions of the conference is to standardize measurements on behalf of consumers.

Critics of the fuel industry want gasoline and diesel retailers to install automatic temperature-compensation equipment on their fuel pumps.

As it stands now, say critics, retailers and oil companies profit from hot temperatures while compensating for temperature fluctuations at every stage of trade, except at the retail pumps.

'This is simply unacceptable,' Kucinich wrote.

The American Petroleum Institute opposes 'temp comp' because it says the cost of retrofitting existing fuel pumps would outweigh the benefits to consumers.