E10 mpg results

AdiG · February 17, 2022

Hi guys did you notice any noticeable difference in mpg since E10 petrol was introduced? With my RC300h F I used to get around 52-53mpg on the old petrol driving to work and back daily 64 miles trip with combined motorway and town driving in eco mode; however on the new petrol E10 I struggle to get around 48-49mpg same driving distance and eco setting?

Monitored a huge difference on other driving modes Normal, Sport and Sport+ as well.

Am curious if anyone else experienced anything similar.

My car RC300h 2017

Thank you in advance

Cypry 1 · February 17, 2022

Definately, I have noticed that between fill ups on my RX450H the distance is between 50 to 70 miles less.

Also about the time that the E10 fuel was introduced there was a fuel crises was this due to the fact that the Petrol companies had loads of the old E5 fuel over and wanted to get rid of it.

malcolmw · February 17, 2022

We have noticed little difference on our NX. However, E10 was introduced just as the temperature was dropping in the autumn/winter season. It may be that this meteorological issue is what is causing the drop in mpg. You may recover range in the summer.

hondansxr · August 17, 2022

i have told 3 people this week alone not to use morrisons fuel full stop .One lady with a 1.4 fiesta is getting low 30mpg from it . Use a PETROL station for your fuel and a super market for your food ...!!!!

hondansxr · August 17, 2022

on a 140 mile run with shell super (and zx1 in the engine) i got 57.2 mpg ...

Linas.P · August 19, 2022

On 2/17/2022 at 5:47 PM, AdiG said:

Hi guys did you notice any noticeable difference in mpg since E10 petrol was introduced? With my RC300h F I used to get around 52-53mpg on the old petrol driving to work and back daily 64 miles trip with combined motorway and town driving in eco mode; however on the new petrol E10 I struggle to get around 48-49mpg same driving distance and eco setting?

Monitored a huge difference on other driving modes Normal, Sport and Sport+ as well.

Am curious if anyone else experienced anything similar.

My car RC300h 2017

Thank you in advance

I am still surprised that people are surprised about this. Yes E10 fuel consumption is higher, because there is less "fuel" in it. Ethanol has 30% less energy density compared to Petrol, so E10 fuel consumption has to be at least 3% higher.

MPG is kind of silly measurement because it is not as obvious that 3MPG difference over 50 is very small (~5%), where same MPG differences between say 10 and 13MPG is huge (like ~25%). So let's just say your MPG dropped from 52 to 49, (5.4L to 5.7L/100km) and that is ~5% difference. Now yes - that is higher than 3%, but we talking about couple of % variance between different batches of fuel and maybe slightly different weather, maybe it was hotter or colder, maybe A/C had to work harder, maybe there was slightly more traffic on few days, so that difference is in line with expectations.

Basically, this is normal and that E10 is less fuel efficient is not some sort of fringe theory it is fact.

Bluemarlin · August 23, 2022

I don't notice much difference between most E10/E5 petrol, but do notice that I get up to 5mpg more with Esso E5, which is zero ethanol. As per Linas' comments, this is to be expected.

wharfhouse · August 23, 2022

Done around 20,000 miles now since E10 came in and so can make a reasonable comparison between E10 Unleaded and E5 Super Unleaded - 90%+ of my fuel is from my local Sainsburys so best like-for-like comparison I can make as I know different brands will also produce different results. Also many of my journeys are the same, ruling out that variation as much as possible.

Initially when moving to Sainsburys E10 last year there wasn't an initial drop in mpg over the old Sainsburys E5 normal unleaded, but as time went on I did start to see a drop off in average mpg (not just being winter months as I had plenty of other years to compare to). One day (during the fuel shortage) I needed petrol urgently and my Sainsburys only had E5 Super Unleaded but the price was no more than the branded E10 in other places and so I filled an empty tank with this and I saw a marked improvement in mpg, some 10%.

In previous years I had tried the Sainsburys E5 Super Unleaded (pre-E10 Unleaded coming out) and although there was a small improvement in mpg it didn't warrant the additional cost. However, the mpg improvement between Sainsburys E10 Unleaded and E5 Super Unleaded was close to 10%. I confirmed this wasn't just an anomaly by using Sainsburys E5 Super Unleaded over numerous tankfuls.

As the difference in price between E10 and E5 Super at Sainsburys is only about 5% I have now switched to using their E5 Super Unleaded permanently as it is now costing me less to use their E5 Super Unleaded than their regular E10 Unleaded.

Of course, this only holds true if the cost difference between E10 and E5 Super Unleaded is around 5%, which is the case at Sainsburys, but unfortunately for the major brands this is not the case with the E5 being 10%+ more expensive, and so if filling up at one of the other major brands I just stick to E10 there.

Anyway, in summary E5 Super Unleaded will deliver something like 10% better fuel consumption than E10 (at least in my IS 300h) and so whether one buys E5 Super Unleaded over E10 IMHO comes down to the price difference between the two (although the car does also seem to run better / quieter on E5 Super Unleaded).

malcolmw · August 23, 2022

It is interesting that most commentators say they noticed little difference in mpg between E10 and E5 at first. You have had much longer experience than most and have noticed a change. Is this because the ECU "learns" about the new fuel over time? I know it isn't just a dumb algorithm as it adapts to your driving style.

wharfhouse · August 23, 2022

53 minutes ago, malcolmw said:

It is interesting that most commentators say they noticed little difference in mpg between E10 and E5 at first. You have had much longer experience than most and have noticed a change. Is this because the ECU "learns" about the new fuel over time? I know it isn't just a dumb algorithm as it adapts to your driving style.

I suspect that maybe at the outset it wasn't actually E10... in fact at the change over I actually noticed a small improvement in fuel economy on E10 that I couldn't explain. I do wonder whether the fuel companies did something such that the change was graduated so that people didn't see a step change (although there were a lot of complaints in the press). Of course could be the ECU learning too and adjusting, however I would have thought that would only have taken a few hundred miles. However, I can only say that now there is a significant difference between E10 and E5 Super Unleaded - I would have thought that half the difference in improved consumption is the E5 vs E10 and the other half is the 97 vs 95 octane.

AdiG · August 23, 2022

Thank you guys to all your answers. My intention was to check if everybody else noticed a change or if it was just my driving style that impacted the results, not to say that wasn't implying there is a theory or a conspiracy behind far from it 😁 Much appreciated all your comments and time.

We will see if the ECU will learn and adapt to the new fuel in time. At the moment the best I could get was 53.8mpg, that said on a daily basis I am between 43 and 46mpg

Spock66 · August 23, 2022

9 minutes ago, wharfhouse said:

I suspect that maybe at the outset it wasn't actually E10

Good point because the definition is up to 10% and similarly up to 5% for E5, so may actually be less in practice and possibly 0% for some brands of E5 as previously stated.

I would expect the ECU to make any adjustments immediately as it's monitoring for knock in real time and adjusting the timing accordingly each time a cylinder fires.

Linas.P · August 23, 2022

3 hours ago, wharfhouse said:

I suspect that maybe at the outset it wasn't actually E10... in fact at the change over I actually noticed a small improvement in fuel economy on E10 that I couldn't explain. I do wonder whether the fuel companies did something such that the change was graduated so that people didn't see a step change (although there were a lot of complaints in the press). Of course could be the ECU learning too and adjusting, however I would have thought that would only have taken a few hundred miles. However, I can only say that now there is a significant difference between E10 and E5 Super Unleaded - I would have thought that half the difference in improved consumption is the E5 vs E10 and the other half is the 97 vs 95 octane.

That is interesting theory... I never thought about that, but considering how crazy is the world nowadays I would not be surprised. Imagine how sneaky that would be!

Bluemarlin · August 24, 2022

20 hours ago, malcolmw said:

It is interesting that most commentators say they noticed little difference in mpg between E10 and E5 at first. You have had much longer experience than most and have noticed a change. Is this because the ECU "learns" about the new fuel over time? I know it isn't just a dumb algorithm as it adapts to your driving style.

I believe that the premium (E5) fuels also have an enhanced additive package, and so it's possible that they clean things out a bit better, and thus improve efficiency/performance. It would therfore make sense that it would take a few tankfulls for the full benefit to be realised.

Linas.P · August 24, 2022

33 minutes ago, Bluemarlin said:

I believe that the premium (E5) fuels also have an enhanced additive package, and so it's possible that they clean things out a bit better, and thus improve efficiency/performance. It would therfore make sense that it would take a few tankfulls for the full benefit to be realised.

I kind of doubt it... premium fuel is proven to slow down accumulation of all sorts of varnish and dirt in the engine, but they are not proven to clean anything at all. So if one only runs premium fuel - after 100k miles the engine will be cleaner compared to running standard, but if you have engine which was running on standard then premium won't clean it much if at all.

If anything in my experience (and I have documented each tank) I was getting worse MPG on premium than on standard all the time. So I think the MPG difference between normal premium vs. normal standard is nothing more but placebo. That said using premium now will have better fuel efficiency, because it is simply more power dense than ethanol.

Finally... I don't mind ethanol as long as it is priced accordingly and for E10 that should be like 5% cheaper than regular fuel, but NO - it costs the same if not more. What a ridiculous time - now we paying same price for fuel which has 3-5% less of THE FUEL in it, or we have to pay ~10-20p more per litre to get premium fuel. This was scam of the century for the government and oil giants, using some ecomentalist nonsense environment scam they win either way, we lose either way. They selling us worse fuel and less of it for the same price, or they taking extra to sell us the proper stuff...

Ian Mack Rc300h F Sport · September 13, 2023

On 8/17/2022 at 11:05 PM, hondansxr said:

i have told 3 people this week alone not to use morrisons fuel full stop .One lady with a 1.4 fiesta is getting low 30mpg from it . Use a PETROL station for your fuel and a super market for your food ...!!!!

Very interesting post. I recall that when I worked in the armed forces we were barred from refuelling white fleet vehicles and hire cars at Morisons for quite a period of time. Read into this what you will.