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Why do some supermarket fuels give lower mpg?

I have noticed a considerable difference in mpg when using some supermarket fuels compared to Shell V-power. Is this due to supermarkets buying low grade fuel to keep their costs low ? What is exactly added to Shell/BP fuels ?

Asked on 30 April 2016 by Rob72

Answered by Honest John
Shell V-Power Nitro Plus is higher octane, so it gives more torque at low revs and more power at high revs. If you use the greater torque at low revs to upshift earlier then you can enjoy maybe a 10 per cent improvement in economy. That pays the extra cost of the fuel. So the other benefits of a clearer fuel system (valves and injectors) comes FoC.

Real MPG enables you to register the fuel economy you are actually getting against your make and model of car, its engine and type of transmission.

Every time you enter an average consumption figure against your car, the overall average automatically adjusts to reflect it.

Real MPG
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