Fuel quality

[SinglePointSafety]

There have been some interesting comments on this forum regarding the effect of different fuel grades on fuel economy and perceived smoothness/performance/noise levels of the Yaris 1.5 hybrid engine in the Yaris and Yaris Cross. As a STEM professional, I have zero tolerance of voodoo science: it's got to be a combination of science-based modelling and empirical evidence. The earth isn't flat, the moon landings weren't faked, Covid wasn't a hoax or caused by 5G, and vaccines actually work....get over it

So I tried to do an experiment. What follows wouldn't get past the first stage of a rigorous peer review, so bear that in mind. I wanted to eliminate the placebo effect i.e. I know I've put super-unleaded in the tank, so I drive differently and convince myself the engine is smoother/quieter/more responsive.... So what I did, for the last 4000 miles I re-fuelled when the gauge was showing nearly empty and Mrs SPS filled the car BUT without telling me what fuel she chose (E10 or 'E5/super-unleaded'), choice dictated by coin flip

Fuel economy: OK, this wasn't easy tank-to-tank because of varying weather/driving patterns etc, so the best I could do was to select individual journeys using the App (hybrid coaching) because many journeys are repeated regularly. All of these journeys using higher-grade fuel showed higher mpg than those with E10, and the average was 5% improvement. BUT, this was a limited number of journeys/data points, not a proper controlled experiment (that peer review committee would be shredding me by now) and the variation was 3-8%

Now this is where it gets interesting: I noted my (entirely subjective, yes, I admit) observations regarding my perception of the aforementioned engine characteristics. My prior expectation was that there would be no statistically-significant correlation....but lordy, to my surprise, I was wrong. When I perceived the engine's performance to be smoother/quieter/more responsive, it was 100% correlated with the higher-grade fuel. Performance, yes, I might expect, simple science explanation of energy content per litre, other characteristics.... I dunno. The difference wasn't huge (the engine's pretty quiet most of the time anyway and acceptably smooth) but noticeable. Others on this forum (thanks anchorman in particular) have explained why this might be so

Like I said, this is far from a properly-controlled double-blind experiment, with the added 'bonus' of some subjectivity so please don't flame me for the obvious shortfalls in my evidence gathering. E10 clearly has some environmental benefits, so it's an 'interesting' choice we have. I'd be interested to hear others' experiences using different grade fuels

[anchorman]

Crikey, you’re on thin ice bringing this up, I got a “how dare you” quickly followed by a luvvie revert to the poor and mental health.  
 

if you follow the logic you should get a modest improvement in economy although never usually enough to make up for the increase cost and it should be quieter because the engine management computer can and will advance the timing without knock.  The big benefit for me is keeping the system clean.  Before I get lambasted, if somebody prefers supermarket fuel, been using it for 40 years, had 20 cars no problem etc etc, crack on.  

[CPN]

Dare I say.... I completely agree with you!

 

[Chas G]

@anchorman 

Before I get lambasted, if somebody prefers supermarket fuel, been using it for 40 years, had 20 cars no problem etc etc, crack on.

Definitely keep "cracking" on, without that we wouldn't have any petrol 😁

@SinglePointSafety interesting post and 4000 miles seems a reasonable comparison.

 

[SinglePointSafety]

Thanks anchorman, CPN: - yes, I fully expected the increase in mpg and, as you say, that the modest increase wouldn't justify the premium price for non-E10 fuel. What I don't have an explanation for is why the engine feels smoother and quieter when the timing is advanced by the engine's ECU: I'm hoping someone here with, I dunno, a PhD in combustion science or 'something' can enlighten us (or tell me I'm delusional, fair enough)

[CPN]

1 hour ago, SinglePointSafety said:

Thanks anchorman, CPN: - yes, I fully expected the increase in mpg and, as you say, that the modest increase wouldn't justify the premium price for non-E10 fuel. What I don't have an explanation for is why the engine feels smoother and quieter when the timing is advanced by the engine's ECU: I'm hoping someone here with, I dunno, a PhD in combustion science or 'something' can enlighten us (or tell me I'm delusional, fair enough)

As Don has already said, less knocking (detonation) meaning less out of balance forces and hence smoother up and down motion of the pistons without any judder (caused by pre-detonation - "knocking").

[SinglePointSafety]

In theory the ECU is supposed to adjust the ignition timing so that pre-detonation doesn't happen: it's bad for the engine and thus 'not allowed'. Hmmmm..... I think I'll go away now and do a bit more research on this: where I work I can tap into the expertise of engineers, chemists, physicists.... pretty much the whole of the STEM circus. If I find anything useful I will report back

[MikeSh]

13 minutes ago, SinglePointSafety said:

In theory the ECU is supposed to adjust the ignition timing so that pre-detonation doesn't happen

Exactly. There must be something else in play. I wonder if E10 burns faster, without detonating, or perhaps slower even, giving the power stroke a different feel.

[anchorman]

Not so much E10 but the octane rating.  It works the opposite to what seems logical.  The lower the octane, the more volatile it is.  That’s why the timing must be retarded.   

[CPN]

Did you mean retarded Don? 🤣

[anchorman]

3 minutes ago, CPN said:

Did you mean r e t a r d e d Don? 🤣

That’s exactly what I meant Colin.  Careful, somebody will report you to admin 🧑‍💼😂

[CPN]

Phewy! Let 'em try!! 

[FROSTYBALLS]

Posts edited with the correct term inserted ....

[CPN]

7 minutes ago, FROSTYBALLS said:

Posts edited with the correct term inserted ....

Yessss!! 

[Trewithy]

Higher octane fuels burn more slowly.  That's why the engine feels smoother and that's why you can have ignition earlier in the cycle.  The aim with all fuels is to get the maximum expansion of the air/fuel mixture just after TDC (Top Dead Centre) to maximise the downward pressure on the piston.

When I say higher octane fuel burns more slowly the difference is minuscule.  Everything happen so fast within the engine.  If my maths is correct then at 3000rpm each piston goes up and down 50 times in a second.

[TonyHSD]

The quality of the fuels depends not only on the fuel itself but also how have been stored in the forecourts tanks and then on what liquid exactly been pumped into our tanks, this is sometimes that most people just don’t think off but it is so important. It’s like you are buying an engine oil from a big barrel and pumped out by some employees, god knows what you will get ….
I had worst ever experience with premium higher octane petrol bought from London’s texaco garage long before the E10 standard.
Filling my tank every two days I often notice a difference in engine noise, response and performance. While the most significant of these three is the noise , then throttle response and lastly the performance which is actually how light the car feels and you only got that noticed if you drive sensibly and not on full throttle. If you smash the pedal to the metal there is 0 difference in performance, but if you drive sensible with safe and efficient manner you will feel your car lighter and more agile with the better petrol in. , if the fuel is bad you will likely feel your car like has been loaded with extra passenger or luggage. 

[SouperChris]

On 4/5/2024 at 8:28 PM, SinglePointSafety said:

There have been some interesting comments on this forum regarding the effect of different fuel grades on fuel economy and perceived smoothness/performance/noise levels of the Yaris 1.5 hybrid engine in the Yaris and Yaris Cross. As a STEM professional, I have zero tolerance of voodoo science: it's got to be a combination of science-based modelling and empirical evidence. The earth isn't flat, the moon landings weren't faked, Covid wasn't a hoax or caused by 5G, and vaccines actually work....get over it

So I tried to do an experiment. What follows wouldn't get past the first stage of a rigorous peer review, so bear that in mind. I wanted to eliminate the placebo effect i.e. I know I've put super-unleaded in the tank, so I drive differently and convince myself the engine is smoother/quieter/more responsive.... So what I did, for the last 4000 miles I re-fuelled when the gauge was showing nearly empty and Mrs SPS filled the car BUT without telling me what fuel she chose (E10 or 'E5/super-unleaded'), choice dictated by coin flip

Fuel economy: OK, this wasn't easy tank-to-tank because of varying weather/driving patterns etc, so the best I could do was to select individual journeys using the App (hybrid coaching) because many journeys are repeated regularly. All of these journeys using higher-grade fuel showed higher mpg than those with E10, and the average was 5% improvement. BUT, this was a limited number of journeys/data points, not a proper controlled experiment (that peer review committee would be shredding me by now) and the variation was 3-8%

Now this is where it gets interesting: I noted my (entirely subjective, yes, I admit) observations regarding my perception of the aforementioned engine characteristics. My prior expectation was that there would be no statistically-significant correlation....but lordy, to my surprise, I was wrong. When I perceived the engine's performance to be smoother/quieter/more responsive, it was 100% correlated with the higher-grade fuel. Performance, yes, I might expect, simple science explanation of energy content per litre, other characteristics.... I dunno. The difference wasn't huge (the engine's pretty quiet most of the time anyway and acceptably smooth) but noticeable. Others on this forum (thanks anchorman in particular) have explained why this might be so

Like I said, this is far from a properly-controlled double-blind experiment, with the added 'bonus' of some subjectivity so please don't flame me for the obvious shortfalls in my evidence gathering. E10 clearly has some environmental benefits, so it's an 'interesting' choice we have. I'd be interested to hear others' experiences using different grade fuels

I ran a few tanks of expensive fuel. Unblinded I noticed absolutely no difference in any useful, or other, measure. Performance won't change as it largely depends on electric, not fuel. Consumption did not change. No difference in smoothness. What is very clear, to a statistician, is that statistical significance is not useful: economy was better p< 0.05 is not a measure of improved economy. 

 

If you want to demonstrate a difference, you must first state what difference means, then run a designed experiment. My own unblinded experiment convinced me that even when I know what fuel I use, there is no meaningful difference.

[mpm235]

I only use BP Ultimate E5. This is because (a) I have a BP Loyalty Card and almost have enough points for a multipack of Kronenbourg 1664 and (b) E10 Petrol is eco-mentalist voodoo claptrap, made out of Moonshine and Greta Turdberg's wee. 

[SinglePointSafety]

Chris, totally agree with what you say regarding the statistical analysis assumptions (I was tempted to use Bayesian rather than frequentist approach with an assumed model of a Normal pdf for the variation in economy) but of course the poor control over the experimental parameters and the relative paucity of the data meant that any 'sophisticated' analysis was totally inappropriate. I never claimed that this 'experiment' met any reasonable standards of rigour, it was simply an attempt to see if a real (mpg) or subjective difference (driving characteristics) could be discerned

I won't be submitting this study to a learned journal any time soon! (mind you, the flat earthers might like it....)

[Mjolinor]

The big problem with modern petrol is the "shelf life". Much over a month and it is knackered. Whoever thought that putting butane in was a good idea should be shot.

 

[Roy124]

6 minutes ago, Mjolinor said:

The big problem with modern petrol is the "shelf life". Much over a month and it is knackered. Whoever thought that putting butane in was a good idea should be shot.

 

How my lawnmower man makes his money, cleaning fouled fuel systems each spring.

[jthspace]

This may be of interest, ref availability and additive.  If you've got petrol garden tools as well. Applies to my 1993 MX5

E5 phased out in Europe

A recent tour to Ireland has raised a serious concern regarding fuel availability in the EU for Veteran, Vintage, Classics and some cars built up to the early 2000s.

Many of you will know that E5 (98/99 Octane fuel with 5% ethanol) is currently being phased out in the EU and will continue to be less and less available.

Although the roll out of this crazy policy was due to start rolling out in Ireland in July, E5 fuel is now no longer available in Ireland – at all. Only diesel and 95 Octane E10 are sold, and a 99 Octane E10 is available in densely populated areas, but it is seriously hit and miss. Surprisingly, there has been little publicity, warnings, or knowledge among the locals and Ireland’s AA has assured people with Classics that their cars ‘should’ be fine on E10, when all experts say they won’t be!

In almost all motorway filling stations in France, E5 is no longer available, but it is available in most rural areas.

Where E5 is no longer available, a high octane E10 grade called Super Plus is often available. Please note whist Super Plus carries the correct octane rating, it still has 10% Ethanol content, which is no good for the cars described above, as the corrosive effects of the low lead, high ethanol content remain.

For France, there is a website (in French only) that lists every fuel station and which grades of fuel they carry. If you require E5 you can select that grade and it’ll show where the nearest fuel station is. You can visit this site here – www.prix-carburants.gouv.fr/

In Ireland, those travelling with classic or vintage cars will face significant trouble if you are not prepared. We struggled to find octane booster and ethanol protector, as they were scarcely available, despite the AA Ireland saying they are widely available. Therefore, we urge all visitors to Ireland with vehicles unable to run on E10 fuel to bring the necessary additives with them.

Please note that if your car is not E10 complaint, the advice is to carry with you in the car, at all times, a good quality Octane Booster product, such as Millers VSPe Power Plus or similar – this is a combination of an Octane Booster and an Ethanol Protector. This means you can fill up with E10 95 octane, and then add the additive. In the event you can buy E10 Super Plus, you will still need an Ethanol Protector product such as Millers EPS Ethanol Protection System Fuel Additive Treatment Additive, which is endorsed by the Federation of British Historic Vehicle Clubs. (This is not an advert for Millers!)

Experts agree that where there is no option, filling up with a tank of 95 octane E10 will not cause damage in isolation but you need to refuel with E5 as soon as possible or use an additive on the next fill.

You should consider upgrading your fuel system to be able to handle E10, which includes compatible fuel lines and carburettor components, but this will not counter the effects the high ethanol has on the engine, so you will still need to run an ethanol protector additive, especially if your car stands for long periods of time.

 

[Rhymes with Paris]

2 hours ago, SinglePointSafety said:

mind you, the flat earthers might like it....)

One has to remember that the flat earth society claims to have various branches around the globe.

 

[SouperChris]

2 hours ago, SinglePointSafety said:

Chris, totally agree with what you say regarding the statistical analysis assumptions (I was tempted to use Bayesian rather than frequentist approach with an assumed model of a Normal pdf for the variation in economy) but of course the poor control over the experimental parameters and the relative paucity of the data meant that any 'sophisticated' analysis was totally inappropriate. I never claimed that this 'experiment' met any reasonable standards of rigour, it was simply an attempt to see if a real (mpg) or subjective difference (driving characteristics) could be discerned

I won't be submitting this study to a learned journal any time soon! (mind you, the flat earthers might like it....)

Would you do it again unblinded? Because the only thing that really matters is if you prefer it. 

Don't get me started on peer reviews; I have to do one tomorrow 🫤. I'm a strong believer that peer review should go the way of the 🦤

 

[SinglePointSafety]

Chris, I have no intention of repeating the experiment (effort >> reward) !

And FWIW I'm a great believer in rigorous peer review when done properly and promptly by appropriate experts. But yes, doing them (and being on the receiving end) isn't always deep joy