Re: I think it's missing some of the additives needed for a car engine
Jet -A! is mainly kerosene which has additives to lower its freezing point.
It is generally of a *higher* quality than road diesel fuel.
You could safely add it to you r diesel mix in winter to achieve a lower waxing (freezing) point in extreme weather.
That's what I got from 10 years working offshore in petrochemicals, flying to work in all kinds of conditions in helicopters of varying size and power....