E10 Regular Unleaded Fuel - First Experiences.

By Stephen George


A Big Change for Petrol at the forecourt ...

Image courtesy of CoventryLive



As I am sure members are fully aware from 1st September all “Regular” 95 RON petrol sold in the UK must contain 10% Ethanol from a sustainable production source. This doubles by volume the amount of Ethanol in each Litre of the cheapest grade of road fuel available.


There has been a great deal published about the various effects of Ethanol in fuel because of course, we have been using E5 or 5% Ethanol fuel for many years and I freely admit, that despite all the doomsayers, I am a supporter of Ethanol blending on the basis that I have grandchildren and I care about the world we will leave them.


I would also stress here that some of the issues with E5, water absorption and solvent effects on rubber and synthetic rubbers have already been addressed with stabiliser additives and new materials to replace ethanol-soluble rubbers and that these measures will be equally effective with E10 fuel. In particular, I would like to reassure our members that all the NEW fuel system products supplied by the Club, including gaskets and seals in reconditioned Carburettors are fully safe for use with E10 petrol.


However, in addition to being a solvent, Ethanol is also mildly corrosive and will attack certain metals given sufficient exposure. In particular, it will degrade Lead-based solder and as most brass floats are soldered together this could be an issue over time. The good news is that should this occur the float can be reassembled using Silver solder that is not affected by Ethanol in the same way.


Then we come to using E10, which I have discovered has already been introduced by the big supermarket chains. I have to be honest here and say that to date, I have not put E10 in any of my classics, but my 2021 Mazda 3 is now on its second tank full and I have been shocked at the results.


Let's start with the science (nearly) bit: Ethanol has a lower Calorific Value than petrol and that has two effects. The first is good in that it reduces cylinder temperature, this means higher compression can be used with less danger of detonation. In modern super/turbocharged engines, fueling and ignition timing is controlled by mapping and monitoring sensors constantly adjusting for maximum efficiency that should be great and certainly, that has been the case with my Mazda of E5.


But now comes E10 and things seem to be different. The Mazda SkyactiveX engine is very sophisticated, running on petrol as a Compression Ignition engine most of the time which can return amazing economy for a 180BHP + 20BHP Mild Hybrid 2 Litre. As you might expect from Mazda, it also has a very sophisticated display to show you exactly how much fuel you are using. Now comes to the part that surprised me, on the first tank of E10 over the course of 300 miles, the Mazda's average Fuel consumption dropped by over 1 mile per gallon compared with the previous 3000 miles on E5 and the trend has continued, with the next tank full of E10 delivering only 290 miles and a further 1 mile per gallon increase in consumption.


There are some caveats here, firstly my test results are based on only 2 samples so far, secondly, there has been no discernable loss of performance on the Mazda. Thirdly, I do tend to push the envelope when I drive and finally, would I have noticed the change in fuel consumption without the various displays? No, probably not.


To finish on a happy note, at present, all 97 and 99 RON fuels remain at E5.



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