1. It's limited as to what you can cook. Only a few things lend itself to cooking something that can't be watched while you are driving. Ever try to boil water on a manifold? Using foil, even multiple layers, can be iffy as foil tears easy. You may find your meal dripping down the engine block, or falling off and a few miles back feeding scavenger birds and coyotes. Many need stirring or turning. This can be very inconvenient on the road.
2. Cooking food needs a constant temperature. Many dishes need certain temperatures and certain cooking times, and food can be ruined by overcooking, too high or too low temps. While an engine may reach a certain temperature, as will a manifold, this temperature is usually only constant while the vehicle is running and only shortly after it stops. Another thing to consider is the outside temperature. A very cold, snowy day or a very hot, summer day will change the temperatures around the engine/manifold as well. A problem with this could be uneven cooking.
3. Vehicle engines/manifolds are not built to cook on. In my car, the manifold itself (which is part of the exhaust system) is slanted and difficult to get to, which doesn't lend itself to holding anything for cooking. Also, my engine is covered by a plastic safety cover over the spark plugs and wires. It doesn't get hot enough to cook anything. Cooking while stopped means idling your car, which isn't the best thing for it long-term, not to mention wasting fuel (so much more expensive now than using proper ways to cook).
4. It can be dangerous. Manifolds and engines get very, very hot. If your vehicle is running when you check on or add/remove your meal, you could get caught in a fan. Leaking "dishes" can cause havoc on electrical connections. Messing up a sensor or the computer unit in your vehicle (most all come with those now, even big trucks) can be very expensive to fix.
5. It can be unhealthy. Cooking in aluminum can leach substances that can cause health issues. I use aluminum foil to cover things, but rarely to cook in. If you get a hole in your foil, you food could be contaminated by grease, exhaust fumes (and particles), bugs, etc. Not to mention the cooking times and temps that are necessary - some foods are very unhealthy to eat if they are under-cooked and even some overcooked.
|1998 Freightliner Classic XL Engine. You have to climb up on that tire to get to it. |
That engine gets hot enough to cause serious burns.
|Typical car engine and manifold. Not a lot of (clean) places to put your food, even wrapped in foil.|
Those grey pipes in front is the manifold. They get VERY hot.
I recommend the methods as outlined in the book. There are so many safer, healthier options for cooking than taking a chance that could end up disastrous!
Good luck and happy cooking!