Modern V/8's
Dan The Man asked: "What is a synthetic fuel consist of?" There are a number of fuels being developed that arer derived from biomass feedstocks so they are considered "Renewable" fuels. This is a whole subject in itself, but I will stick to "Synthetic" fuel. Ethanol is a renewable fuel maded from fook-based feedstocks, corn or sugarcane. The detriments of ethanol are energy content due to it being already oxygenated, but it does have good octane. But it is only a blend component with conventional gasoline. Ethanol can be dehydrated into ethylene and converted into hydrocarbon fuels including gasoline, jet fuel and diesel fuel, but it takes 2 gal of Ethanol to make 1 gal of hydrocarbon fuel.
A better way to produce renewable fuel is to use Municipal Solid Waste (MSW) or Forest Waste as feedstock. Gasify the feedstock to Carbon Monoxide (CO) and Hydrogen (H2). Then combine over a catalyst and convert CO + H2 into -CH2- groups (hydrocarbons) and water. This is called Fischer-Tropsch synthesis and I have been working in this area for 24 years. You can make OK gasoline this way, but I produce outstanding diesel and jet fuel this way. The diesel is water white, no odor, and 80 cetane, so it works great in any diesel engine. The jet fuel is perfect for blending with conventional jet fuel to may synthetic jet fuel that is being used by airlines all over the world in their quest to lower GHG emissions.
There are a few other renewable fuel production pathways that are being developed, but they are more expensive than the two discussed.
I tried to keep the chemistry simple, but there are lots of issues to discuss here.