If you are interested in building and experimenting with fuel reformers for much better fuel efficiency there is a group of experimenters sharing information at:
formatting link
Fuel reformers are used in the oil industry to make hydrogen. Small units can be built for a car or genset and the refomer's hydrogen content output burns more efficiently giving the equivalent of a big octane boost. Also the waste heat of the engine gets utilized by the reformer so it is no longer wasted.
This group is for experimenters only.
Fuel + steam can be cracked with engine exhaust heat plus a catalyst or a plasma or both together.
formatting link
This technology has been around a long time but car makers won't use it.
Here are some examples:
formatting link
formatting link
formatting link
formatting link
formatting link
Here are many more patents ignored by car makers:
formatting link
Naresh