Use of Vegetable oils as a fuel in a Diesel Engine Surf
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If using SVO, any type of veg-oil will do, Sunflower, Rapeseed, Maize, Corn etc etc. Just use the cheapest as there is little real difference.
What to do if your fuel mix has gelled due to low temperatures....
This would depend on just how cold it is and how thoroughly the fuel has gelled.
Initially the fuel in the lines and pump would gel. More extreme cold could cause the fuel in the tank to gel, in which case there is no quick way to heat it enough to reverse the gelling.
If you suspect the fuel in the lines has gelled, get a kettle of hot water and pour it slowly over your injector lines, fuel pump and any other fuel lines accessible within the engine bay (or use a hair dryer - do not use a heat gun). Then cycle the glow plugs 2 or 3 times, this should enable it to start. Let it idle for at least 5 to 10 minutes after this to ensure all is well, as if the fuel in the tank had gelled this method will probably still allow it to start, but it could later die when it cannot draw the gelled fuel from the tank. Leaving it idle for a while to begin to use the fuel in the tank (and recirculate hot fuel back to the tank) will help ensure it does not die whilst on your journey.
Some owners have experienced a drop in economy when using veg-oil, the following may offer an insight as to why this might be...
The calorific value of Vegetable oils is around 37,000 kJ/kg, whilst Diesel is around 42,000kJ/kg.
This means that Diesel has around 10% higher calorific content per kg, however the rate and measurement of your engines consumption is by volume not weight.
The density of veg-oils is up to 10% higher than Diesel, so the weight of oil consumed is higher than diesel for the same volume, this means the the calorific content available from veg-oil is higher when measured volumetrically, and should be nearly equal to that of Diesel.
A very small loss of energy by volume can be expected, however this is only slight, and should be in the order of 5% at most.
This can therefore translate into a potential drop in economy of up to 5%. This is however assuming a switch to 100% veg-oil. Use of a 50% mix would therefore yield an increase in consumption of up to 2.5%. On a vehicle returning 25mpg, this works out at 0.625mpg worse off, this should hardly be noticeable, and far outweighed by the environmental and monetary savings.
Personally, when I first starting using veg-oil I was keeping records of my fuel consumption and could detect no difference whatsoever.
Other factors can also come into play, comparing energy content is really only relevant if both fuels are to be burned under ideal conditions. Considering the modern compression ignition engine has been tuned to burn fossil fuels, it will therefore offer an injection/combustion process that can prove better suited to diesel when compared to veg oil. This is why certain engine types readily take to veg oil, whilst other may require modification before successful use, and some some not use it at all.
A number of elements are crucial to successful use of veg oil including the fuel pump, the injectors, combustion chamber design and overall condition of the engine. On Surf's the fuel pump is fine and the combustion chamber is not something you're likely to try and modify, of the remainder the injectors are the most influential item. If these are in poor condition, worn, clogged, etc. then whilst not at optimal on the diesel they're designed for, they could potentially be even worse on alternate fuels such as veggie. They may be spraying inefficiently, a problem which would be exacerbated by the higher viscosity of the veg oil.
Injectors in poor condition would certainly be a prime suspect if a vehicle is getting noticeable worse mileage on veg-oil