Sunday, May 01, 2011 at 12:52
For a diesel engine that is designed for a Cetane number range between say 42 and 48, the use of fuels with higher cetane number actually results in slightly worse fuel economy.
The upside of using higher cetane number fuels (ie; Super diesels) is they have a slightly faster combustion which results in apparent smoother engine operation with less diesel knock.
These higher cetane number fuels are specially suited to high speed passenger car diesel engines.
To achieve the higher cetane number fuel formulators have to either reduce fuel density (use lighter components with less energy density), add oxygenated fuels including biofuels, or add esters of low molecular weight compounds such as 2-Ethylhexyl nitrate ( a favourite).
The use of these higher cetane fuels in engine developing peak torque around 2,000 rpm is not warranted.
Recent studies in the US where these fuels have been sold for some time has returned an overall fleet fuel use increase of between 1% and 2%.
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