That seems completely implausible though based on the losses. An ICE tops out at 25% efficient or so. A hydrogen fuel cell is 40-60% and efficient and that's likely to rise. If you're bothering with fueling cars with hydrogen gas, you might as well make them electric and get a huge range boost for free (and way more torque, less maintenance etc.)

There's just no logical reason to try and burn hydrogen in ICE engines.