25% better mpg from current diesels? Too good to be true?

If they could boost MPG by 25%, the auto companies would bid billions for the patent as they could dominate the trucking industry (and other heavy commercial engines) for decades until the patent ran out.

As mentioned, patents aren't secret. They are publicly available. How else would you know if someone already patented an idea? Plus, you can use patented ideas but simply have to pay for them. So if true, it would be worth a court case to open the design to public use.