Quote:
Originally Posted by RoyMacDonald
Shell V + contains more energy than standard diesel so you probably had it diluted with diesel still in the tank if you only had one fill up.
My son in law switched to V + for his motorbike and got an extra 11 mph from it. (139 mph) Runs more smoothly too, Just like my D5 does.
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Higher octane petrol can enable a higher output on an engine which is designed to use it - i.e. a high-compression or turbocharged motor with a knock sensor and comprehensively-mapped ignition and fuelling. In these cases the knock sensor will allow more ignition advance or boost pressure.
It's not as clear-cut with diesel - Shell's own literature for both VPN+ and FuelSave state the same typical 'from the pump' cetane levels. The VPN+ is supposed to have a % of gas-to-liquid (GTL) which is purer than conventional refined fuel, but I don't think they state how much any more.
The filling stations are now switching from winter to summer diesel, which can make a difference too.