Denver ? Backyard grillers may get a little steamed this holiday weekend when buying refilled propane tanks: They will be getting less fuel for their money than last Memorial Day.

When oil prices soared in 2008, propane suppliers quietly reduced by two pounds the amount of gas pumped into each 20-pound tank, saying they wanted to avoid raising prices.

Since then, propane prices have been cut in half as the price of oil has dropped. But smaller refills are still being sold nationwide by many dealers, and most buyers are unaware because the tank is the same size.

“It’s a price increase,” retired lawyer Stuart Barr said Friday as he swapped a tank at a Home Depot store in Denver. “I’m a great believer in full disclosure. Give me the information.”

The problem, consumers say, is that no one tells them they’re getting less propane. Companies have adopted similar practices in the packaging of coffee, sugar and laundry detergent.

For the past year, tank exchanges at retail stores have generally cost $20 to $25. For a few bucks less, consumers can take their tanks to some stores to get them refilled instead of exchanging them. Those refills usually contain the full amount of fuel allowed by law.