SMA retrofit cessnas (and others)

on the website: they have a long-winded CYA letter from exxonmobile essentially saying that they would not certify their jet-A be used in in any "diesel" airplane and they furthermore cited that Jet-A can sludge at cold temperatures . They claim that this is not a problem in big jet airplanes because the friction created by the air moving across the wing surfaces heats the jet-a up enough to keep it from sludging above 12,500 feet.

As a result of these claims, SMA refurbished planes in the USA have to either have a fuel heating system built into the wing tanks or have to state that the service ceiling can be no more than 12,500 feet.....seems rather arbitrary to me and, living in colorado, i can tell you that it can get butt-cold at ground I dont see why there is this artificial limit placed on these retrofitted planes.

BUT...perhaps someone in theese formus knows more than me and can explain it better.
CYA says it all, I think.

I don't have any numbers in front of me, but I would be surprised if something like, say, a Jetstream 32 or Saab 340 receives any significant warming of the fuel from aerodynamic heating.
This is complete horse poop.

Hoar frost is created because of super cooling of the fuel, then introduced at lower, warmer, humid air. This goes against the exxonmobile CYA letter. I'm betting they aren't willing to spend the money developing it.
Hey, look what I found in an unrelated article:

" UOP, a division of Honeywell, refined the jatropha oil into a synthetic jet fuel using a process similar to that for refining typical petroleum fuels. As a result, the fuel is functionally the same as petroleum-based fuel, including not turning freezing until -70.6 degrees Fahrenheit (-57 degrees Celsius)—above the Jet A1 specification of-52.6 degrees F (-47 degrees C), according to chemist Jennifer Holmgren, UOP's general manager of the renewable energy and chemicals business."

So, where the heck does exxon mobil get off saying that you cant use jet-a to power a diesel engine?!?

Here's the whole article for those interested: