In the wake of the Volkswagen emissions test cheating scandal, several auto part makers have come forward to defend diesel-based vehicles.

For the unfamiliar, we reported that Volkswagen had admitted on Sept. 22 that nearly 11 million of the company's diesel cars had a software installed which enabled the German carmaker to cheat in the U.S. gas emissions tests. The software apparently reduces the nitrogen oxide emissions by a diesel vehicle, but only when the car is going through an emissions test.

The scandal got messier last Friday, Sept. 25, when Alexander Dobrindt, Germany's transport minister divulged that close to 2.8 million diesel cars in the country were also affected by the rigging.

With concerns on the viability of diesel vehicles at stake - as well as the risk of disillusioned consumers shifting to electric vehicles or hybrids instead - several car part makers have come forward to salvage the situation.

Honeywell International, Inc.'s CEO Terrence Hahn defended the diesel-powered vehicles saying that the technology was still effective. Honeywell supplies turbo chargers that are frequently deployed to make diesel-based vehicles faster.

"We have seen proven results around clean-diesel technology, and we don't want what one auto maker has done to tarnish the industry or the technology," noted Hahn.

Despite Mr. Hahn's assurances, Wall Street was unconvinced as Honeywell's shares fell by 10 cents on Friday, Sept. 25.

While Volkswagen has apologized for the use of illegal software and promised to overhaul the 482,000 diesel-powered VW vehicles in the U.S as quickly as possible, the damage is already done as is reflected by the dipping share prices of auto part makers.

Even though diesel cars account for less than 4 percent of sales in the U.S., to recreate trust with probable diesel-powered vehicle buyers in the country would be difficult per auto retailers.

"It is another black eye for diesel engines overall," surmised AutoNation Inc.'s Mike Jackson.