A study conducted by VTT Technical Research Centre of Finland indicates that there is practically no difference between commercial petrol grades 95E10 and 98E5 sold in Finland as regards fuel consumption in normal driving. The finding is based on driving tests conducted by VTT using six used cars of different make under laboratory conditions.
It has been frequently claimed in public that fuel consumption is significantly higher with 95E10 petrol than with its predecessor 95E or the 98E5 petrol currently on the market. The suspected higher consumption has deterred drivers of cars whose manufacturers recommend E10 from actually using it.
"The point of this study was to highlight how fuel consumption should actually be measured to give comparable results. Measuring fuel consumption very accurately is not as simple as it seems, because other factors affect consumption besides the fuel itself. In laboratory conditions, we can eliminate these other factors," says Juhani Laurikko, a Principal Scientist at VTT.
The VTT measurements show that the cars tested used an average of 10.30 litres of 95E10 per 100 km, as opposed to 10.23 litres of 98E5 per 100 km. The difference was 0.07 in favour of 98E5 on average, meaning that using 95E10 petrol, which has a higher ethanol content, increases consumption by 0.7%. Normalising measurement results of each individual test run with observed slight scatter in actual total work done over the driving cycle yields to somewhat higher overall difference, 1.0%.
An estimation of calorific values based on approximate fuel composition came out at 1.1% in favour of E5, which is highly consistent with the aforementioned 1.0% difference in consumption. Fuel consumption depends mainly on the calorific value of the fuel, i.e. its energy content per unit of volume or mass.
|Contact: Juhani Laurikko|
VTT Technical Research Centre of Finland