Alternative fuels for vehicles

With UK pump-prices of petrol and diesel heading rapidly towards £7.00+ p/gallon, we need to consider the real possibility of having to think about other ways to power our engines.

The primary two engine types are 'Petrol' and 'Diesel', by design, they are very different beasts that use fuel in totally different ways. Petrol ignites with a spark, whilst diesel compresses the fuel to the point that the molecules within generate enough heat to detonate. Taking this in to account, we need to divide our hunt into two paths, one, fuel that can be ignited by a spark and one where the fuel can be ignited by compression.

Based on the limitations of our requirements, the following are possible alternatives which can run either 'as-is' or via modifications to the engine.

Alternatives for Diesel

• Biodiesel
• Black diesel
• Straight vegetable oil (referred to as 'SVO')
• Waste vegetable oil (WVO)

Alternatives for Petrol

• Bioethenol
• Compressed natural gas
• LPG

Biodiesel is made from waste cooking oil by changing its chemical structure by the use of various chemicals. It can be made at home and there are plenty of sites dedicated to homebrew bio. You do need to understand that not every car can run on 100% biodiesel, so, as with any 'diesel replacement' it should be used with caution.

Pros:

• Can buy reactors for home use
• You can make and use 2500 litres tax-free (UK)
• The waste chemicals from the processing have a sell-on value as the individual chemicals can be recovered and re-used.
• Burns hotter and more efficiently than regular diesel.

Cons:

• Can be hard to get the waste oil.
• Takes over 24 hours to make if done properly.
• You have to filter the waste oil to remove any food waste prior to processing. This needs to be got rid of properly.
• You need to register with HMRC to be legit.
• Can find its way past piston rings and contaminate the engine oil so more regular oil changes are need.

Black diesel is made from waste engine oil, brake fluid, transmission oil and power steering fluid. Basically, the mixture of stuff that gets drained from a car during a service. This is normally thinned-down with white spirit.

Pros:

• Ready supply of raw material if friendly with local garage.

Cons:

• Due to the inconsistantcy of the raw material mix, you have no idea of the final quality
• Needs filtering in stages down to 10 microns.

This fuel is very experimental due to the nature of the initial product. Make/use with extreme caution.

SVO can be used without processing as it is new and unused. WVO on the other hand, requires filtering to remove food waste, then placing in a barrel with a tap on the bottom in order to 'settle'. This allows any water to separate-out from the oil. Due to the fact that oil floats on water, the crap at the bottom of the barrel needs to be drained-off before you can decant the oil into a jerry can.

Not many diesels can run on SVO/WVO without some form of modification. This is due to the thicker viscosity of vegetable oil in relation to diesel. These mods can be as simple as a heated fuel filter or inline preheater, or as complex as a two-tank system (you start on regular diesel, then change over to WVO/SVO when the engine is warm-enough). This is the system that modern diesels need.

WVO/SVO burns better than diesel, but also 'solidifies' at a warmer temperature so is not really suited to winter running without extra inline heaters.