Double-digit diesel sales in North America for 20 of the last 24 months have helped German automakers reach record sales. That is likely to increase as all five - Audi, BMW, Mercedes-Benz, Porsche and VW - roll out more diesel choices, including powerful and fuel efficient turbo versions.

Diesel is a "cornerstone of our portfolio going forward," said William Craven, head of regulatory affairs for Mercedes-Benz parent Daimler, which is introducing a 4-cylinder diesel to the US. He was part of a panel of diesel marketing and regulatory experts speaking at a panel sponsored by the German-American Chamber of Commerce, during the NY Auto Show, which is open to the pubic through April 7.

BMW's Dan Creed, responsible for the brand's product planning in North America, says there will be a diesel "in every [category of vehicle] segment" before 2025, when federal fuel standards require 54.5 mpg average fuel economy. Diesel is an indispensible tool toward meeting that goal because "it's 30 percent more efficient out of the box," said Wayne Killen, Audi of America's manager of product strategy.

"Fuel economy is the number one consideration for our customers," said VW's Doug Skorupski, manager of American product strategy. He said VW is adding a clean diesel option lower priced trim levels than is currently the case to broaden the appeal even further. Just over 20 percent of VW sales in the US last year were diesel, including a whopping 82 percent of the Jetta Sportwagen, and that "success is driving our production plans," he said. Volksagen has long been the leader in sales of clean diesel vehicles in the U.S. It's TDI branded clean diesel vehicles practically have a cult following.

Check out AOL Autos Techsplanation story and video on Clean Diesel and how it works to save on fuel economy. Here.

Audi is adding US diesel offerings. An Audi A8 TDI 3.0 liter V6 capable of 36 mpg and an 800 mile range, the highest in the segment, is in the lineup this year. Killen said the A7 and A5 are also getting TDI power-plants, but did not say when they would arrive in U.S. showrooms.

Porsche marketing vice president Andre Oosthuizen said 30 percent of Cayenne SUV sales are diesel, which "far exceeded expectations." But, he added, there are no plans to offer diesel versions of high performance models like the 911 or Boxster/Cayman. Unlike corporate sibling VW, he said fuel economy is not "in the top five" considerations for Porsche customers today, but expects that will grow.

All five German automakers agreed that the perceived lack of availability and cost of diesel fuel are important considerations, perhaps even deterrents.

The idea that diesel is available only at truck stops "is more perception than reality," said Daimler's Craven, noting that an many fuel stations have diesel pumps, next to the gas, and that on-board navigation systems make them easy to locate.

Audi's Killen said all of his company's models require premium gas, so the higher cost for diesel is less of an issue. Even so, "gas is now the highest percentage of disposable income since the 1980s," he said, making overall cost of ownership a prime selling point.

Benefits of clean diesel in terms of fuel economy and performance are mostly drowned out by buzz around hybrids and electric vehicles, as well as the improving fuel economy of gasoline-powered vehicles and the shift to high-performance 4-cylinder and 6-cylinder vehicles. All five automakers on the panel agreed that it's difficult to convert a gasoline customer, or one considering a hybrid, to diesel in the showroom.

"We need to educate the customer" better that new clean diesel technology is an alternative, not a compromise to performance and value," said Porsche's Oosthuizen, which is the same issue for hybrids and PHEVs.