Yaris Hsd - Super Or Not So Super...unleaded

[Ethanedwards]

Usually I run it on elCheapo Supermarket fuel. Having done 38K in mine over the last two years I know the vehicle pretty well. Last night (on a whim) I filled up with Shell V Performance super unleaded for the first time ever.

Based on the chat on here that you get 10% extra MPG. Not especially scientific proof but on my 35m journey home and in again this morning....tis absolutely true. You do get about 10% extra MPG.

Since it's also about ten percent more expensive than supermarket meths err petrol, I don't think it's actually worth the bother for me. But there it is.

I'm taking it in for it's 40K service 22nd December and I will be buying two more tyres about then as well. The last two original loathsome Conti's being history. And based on GC's advice this time I will be going for two ditchfinders Enegy Eco ones or summat. Try anything once!

My colleague asked me yesterday If I was thinking of changing the car (usually do after two years) and enquired about buying it. I said ''well make me an offer around ten grand'' otherwise I'm keeping it the full five years till the warranty runs out and my GAP policy runs out. Also it's when the Service plan runs out too. That surprised him as he thought I'd be changing it and he could pick it up for five grand or so. Ain't happening ....I like this car and more importantly it fits snugly in my compact and 'bijou' garage where a Prius or Auris just probably wouldn't.

[Grumpy Cabbie]

It's personal choice. It is said that most Super unleadeds don't contain any/as much ethanol as 95 Premium, and thus that helps the fuel economy. (5% ethanol content can reduce mpg's by upto 10%)

Personally I now religiously use Shell VPower. Not because it gives more performance, which it doesn't. But because it runs smoother on the stuff and because it has a higher concentration of cleaning agents than El Cheapo supermarket petrol. On that subject, I had my Prius EGR valve fail at 70k miles because it was totally gummed up with carbon. I have previously just used the cheapest petrol; my local Asda, but will never use the stuff now unless in an emergency.

I might be paying over the odds, I might be fooled by a big petrol station conspiracy, but I notice the car runs smoother, especially so at cold start. Mrs Cabbie also started using VPower for the same reasons (Toyota IQ's have EGR issues too) and even she noticed the smoother running. Also, and it is probably a big coincidence, but her emissions this MOT were 1ppm on hydrocarbons instead of last years 59ppm (out of 200). Nothing has changed, same car, same plugs, same MOT station, but this year after 6 months of Vpower her emissions were lower.

But for every convert there is someone saying petrol is petrol, it all has to comply with the same regulations and El Cheapo supermarket grade is fine and to pay any more is foolish.

It's your call.

[PeteB]

... Personally I now religiously use Shell VPower...

Do you mean you're on your knees when you fill up?

[Cyker]

Woah what? I thought EGRs sooting up was a diesel problem, but you're saying it happens to petrol cars too?!

[Grumpy Cabbie]

Woah what? I thought EGRs sooting up was a diesel problem, but you're saying it happens to petrol cars too?!

It was a £400 replacement too as it's a cooled egr (or something like that) and the whole unit including tube thingies were all gummed up.

But yes, to reduce NOx emissions I believe egr's are now found on more and more newer cars. Just look at the sticky on the IQ forum. That car has suffered all sorts of issues because of the egr.

[FROSTYBALLS]

See http://www.toyotaownersclub.com/forums/topic/147454-egr-problem/

[kithmo]

I used to use V-power every time in the Gen 3 as it ran smoother, although it didn't make any difference in mpgs.

Now with the Plus I use Shell fuelsave as it doesn't seem to make any difference in smoothness and it actually feels more responsive in eco mode with Fuelsave rather than with V-power. Mpgs are the same with either in normal mode and better on fuelsave in eco mode. I still run two or three tankfuls of v-power through now and again for it's extra cleaning power.

[FROSTYBALLS]

We usually use Shell FuelSave or BP Regular - though if we're doing a distance trip, I tend to use V-Power or BP Ultimate.

Do occasionally use Tesco fuel - where they have an offer on giving some off the price of petrol having spent an amount on groceries or their current Fuel Save promotion, and then we use Momentum for the better additive package.

[Joseph D]

I'm not sure whether it is really true that higher octane fuel has better cleaning properties or not. I'm of the impression that it has been repeated so often that it has become accepted as true, so full kudos to the marketing people for a job well done. :)

On the subject of 98/99 RON vs 95RON, I wrote an extensive post HERE, and don't feel inclined to repeat it so have linked to it for those that are interested.

I'd like to add, that since conducting my little experiment, I decided to stick with Shell Fuelsaver 95, not for any other reason than consistency. Since then, I have steadily improved fuel economy, but also note, that tank to tank, I have had variations (outside of those that can be explained by seasonal differences). I feel I can safely say that there will be another explanation for variance in fuel economy other than that which can be simply explained by the use of fuel X vs fuel Y.

I'd say that if you are serious about investigating these issues, make detailed records (Fuelly is a good platform) and you will quite easily bust those myths for yourself.

And by all means, continue to spend on premium fuels if that makes you happy.

My £0.02, hope that helps.

[FROSTYBALLS]

Copied from Tesco's blurb on their fuels:

Our three main grades are Tesco Unleaded, Tesco Diesel and Tesco Momentum⁹⁹ Super Unleaded.

All our fuels are refined on our behalf with performance additives and detergents designed to clean and protect your engine. The largest additive package is added to our exclusive 99 Octane Super Unleaded -Tesco Momentum⁹⁹. The base fuels which we use conform to and are tested regularly against the following British Standards:

• Tesco Unleaded (BS EN228)
• Tesco Diesel (BS EN590)
• Tesco Momentum⁹⁹ Super Unleaded (BS EN7800)

[Cyker]

Higher Octane fuel by itself doesn't have better cleaning properties; The only reason 'super' fuels like V-Power and such do is because they add more cleaning agents into the mix.

The downside is there is a little less energy per litre as the cleaning agents are not fuel.

[MEP's Yaris GS]

Cleaning agents are a big spin off imo. Petrol in any form is a solvent that'll clean most things, and I've used it in the workshop as a cleaner along side white spirit etc. So being cleaner for your engine is snakeoil imo.

Although I'm not disagreeing that it'll run better and possibly give better MPG due to the different additives in premium fuel over standard fuel.

[Joseph D]

... The downside is there is a little less energy per litre as the cleaning agents are not fuel.

Actually, it is most likely because it has a higher RON, rather than the detergents.

And to be clear all fuel have detergents in them because that is mandated by regulation.

[Grumpy Cabbie]

... The downside is there is a little less energy per litre as the cleaning agents are not fuel.

Actually, it is most likely because it has a higher RON, rather than the detergents.

And to be clear all fuel have detergents in them because that is mandated by regulation.

And has been said before, all fuel has the legal minimum mandated by regulation. Others have additional additives. I'm guessing the additional additives are more expensive, hence the higher cost.

I have never had an engine snarl up like the Prius when using Asda's finest. I always used Shell and BP in the past but bought the 'all fuels are the same' line and used Asda to save 50p a tank. It cost me in a gummed up engine. I now have gone back to Shell and my engine now runs smoother. It runs slightly better on VPower than 95 at cold.

But again, it depends on your use patterns. If you whizz down motorways all day then Asda fuel is probably fine. If you do lots of cold starts and use the car in town for a couple miles at a time, then I've found VPower better. Not better economy as that seems pretty much the same as before, not better performance as the car doesn't differentiate, but better smoothness as it's cleaned the gunk out of the fuel system.

It's a marmite issue. Some are totally unconvinced, others totally convinced and many sitting on the fence not really bothered either way. I was one of those but fell onto the convinced side :)

[Joseph D]

... The downside is there is a little less energy per litre as the cleaning agents are not fuel.

Actually, it is most likely because it has a higher RON, rather than the detergents.

And to be clear all fuel have detergents in them because that is mandated by regulation.

And has been said before, all fuel has the legal minimum mandated by regulation. Others have additional additives. I'm guessing the additional additives are more expensive, hence the higher cost.

I have never had an engine snarl up like the Prius when using Asda's finest. I always used Shell and BP in the past but bought the 'all fuels are the same' line and used Asda to save 50p a tank. It cost me in a gummed up engine. I now have gone back to Shell and my engine now runs smoother. It runs slightly better on VPower than 95 at cold.

But again, it depends on your use patterns. If you whizz down motorways all day then Asda fuel is probably fine. If you do lots of cold starts and use the car in town for a couple miles at a time, then I've found VPower better. Not better economy as that seems pretty much the same as before, not better performance as the car doesn't differentiate, but better smoothness as it's cleaned the gunk out of the fuel system.

It's a marmite issue. Some are totally unconvinced, others totally convinced and many sitting on the fence not really bothered either way. I was one of those but fell onto the convinced side :)

I've never used Asda fuel, so can't comment. My foray into supermarket fuels was only Sainsbury's and Tesco and never used enough to gum up anything. Of the mainstream fuel co's, I have used Shell, BP, Esso, Total and Gleaner, all RON 95, and have not really noticed any significant difference between them, except the Gleaner -- but that was only one tank (61 MPG) and that was better than the tanks before and after.

I am exclusively using RON 95, primarily Shell Fuelsave 95, and I've never had the engine snarl up so am thinking it is a good tipple.

I did experience a noticeable and consistent improvement using European fuel, on two different trips to Europe, always RON 95, except for one tank of RON 98 in France because 95 was unavailable. Interestingly the trips to Europe were in a loaded car, 2 adults and luggage in one trip and three adults and luggage in the other, and still better fuel economy than in Britain. Was it the fuel or the load? Can't say. The Total S98 was noticeably higher consumption (53 mpg) compared to the several tanks before (avg 59 mpg).

It maybe a marmite issue. I'm one of those totally unconvinced.

[Cyker]

Well the lower energy content is purely because of stuff added to the fuel. Cleaning agents are just one part, but octane boosters are another.

If you could have petrol that had a naturally high RON then it wouldn't have a lower energy content necessarily, but if just 5% of the fuel was replaced with cleaning agents and octane boosters etc. that would lower the energy-per-litre available by a noticeable amount.

As for the fuel quality, I think it depends on the duty cycle of the car; If you're hauling ***** over the motorways and such all day then I suspect any old fuel will do as the engine will get hot enough to burn off any crap internally.

For cars that mostly do short journeys or the engine has a much lighter load (e.g. city-driven diesels and HSDs) better quality fuel does help stave off crud build up due to the engine never getting hot enough to burn it off.

When I say better quality I'm not talking about the Octane tho', but what else is in the fuel (Cleaning agents, injector lubricants, corrosion inhibitors etc.). Higher octane might give a tiny performance boost to some cars, esp. if you live at low altitude, but unless the car is set up for it with a higher compression ratio you don't get much of a benefit, and because it has a lower energy content due to all the additives replacing a fraction of the fuel, it can even give less power!

(It's a bit different with diesel; All diesel engines, but esp. high RPM ones like the D4D, benefit from better cetane ratings because it allows the fuel to ignite faster and burn more completely. Unfortunately it turns out most of the higher cetane rating diesels get that by having loads of additives in them, which lowers the energy-per-litre so you don't really gain as much as you'd hope! I'm still too chicken to try the 2-stroke thing on supermarket diesel )

[Grumpy Cabbie]

For cars that mostly do short journeys or the engine has a much lighter load (e.g. city-driven diesels and HSDs) better quality fuel does help stave off crud build up due to the engine never getting hot enough to burn it off.

When I say better quality I'm not talking about the Octane tho', but what else is in the fuel (Cleaning agents, injector lubricants, corrosion inhibitors etc.). Higher octane might give a tiny performance boost to some cars, esp. if you live at low altitude, but unless the car is set up for it with a higher compression ratio you don't get much of a benefit, and because it has a lower energy content due to all the additives replacing a fraction of the fuel, it can even give less power!

I was wondering about compression ratios. The Prius has a ratio of 13.0:1 which if I recall is quite high for a petrol. I am probably wrong but are some diesels not much off that at about 15.0:1?

Perhaps that's why the Prius runs smooth on the expensive stuff?

[FROSTYBALLS]

Examples of compression ratios:

Auris 1.33 11.5:1 (both generations)

Auris 1.6 10.7:1 (both generations)

Auris & Yaris 1.4D4D 16.5:1

Auris 2.0D4D 15.8:1 (first generation)

Auris 2.2D4D 15.7:1 (first generation)

Auris Hybrid 13.0:1 (both generations)

New Aygo 11.5:1

Yaris 1.0 11.0:1

Yaris Hybrid 13.4:1

[Ethanedwards]

Cheese and Crackers! My Yaris HSD has a 13.4 to 1 compression ratio? I've bought a flipping Diesel Hybrid!

[FROSTYBALLS]

The new Atkinson cycle 1.0 litre and 1.3 litre engines that Toyota will be introducing by the end of 2015 (the 1.0 litre will replace the current 1.0 litre engine in the Aygo for example) will have a higher compression - the 1.3 having a compression ratio of around 13.5:1.

Mazda's new Sky Activ G engines will have a compression ratio of 14:1 - http://www.mazda.com/technology/skyactiv/engine/skyactiv-g.html

[Joseph D]

The new Atkinson cycle 1.0 litre and 1.3 litre engines that Toyota will be introducing by the end of 2015 (the 1.0 litre will replace the current 1.0 litre engine in the Aygo for example) will have a higher compression - the 1.3 having a compression ratio of around 13.5:1. ...

So what RON rating does Toyota recommend for these new engines?

[FROSTYBALLS]

Don't know.

[Grumpy Cabbie]

It'll be 95 RON. Nobody will buy a non performance car that uses 98 only.

I'm more concerned at how a 1.0 atkinson cycle non hybrid car can keep up with traffic. Isn't that the reason the Prius is a hybrid; it uses the much more efficient atkinson engine for better economy whilst using the electric motor to aid in acceleration? Without the hybrid system an atkinson cycle engine would be an economical slug.

[Grumpy Cabbie]

Cheese and Crackers! My Yaris HSD has a 13.4 to 1 compression ratio? I've bought a flipping Diesel Hybrid!

That's why you get diesel economy whilst driving at a steady 60 mph. If you don't already know about them, look up 'atkinson cycle' petrol engine.

http://en.wikipedia.org/wiki/Atkinson_cycle#Vehicles_using_Atkinson_cycle_engines

[Cyker]

Are you sure those figures are right Frosty?

My Yaris D4D says it is 17.5:1 and that was considered pretty low at the time; Most bigger engine diesels at the time, at least VW ones, were up in the 20:1 area IIRC!

I know Toyota's tend to have lower ratios tho' as they realised lower compression ratio = less cylinder pressure = can use aluminium instead of steel = lighter components etc.

It does mean some efficiency is lost but it's balanced out by the gains from the lower reciprocating masses/weights and is why the D4Ds have unusually high rev ranges for diesels.

The Mazda's 14:1 is the lowest I have seen tho'; I bet that'll be a absolute ***** to start in sub-zero weather without some seriously powerful glowplugs!

As for the Atkinson cycle thing, it's a bit misleading - The compression ratio is not actually 13.5:1 or it'd be detonating on a fairly regular basis without some ignition timing kludging.

The thing with the Atkinson cycle is the compression stroke and expansion strokes are asymmetrical (i.e. not the same):

The expansion ratio uses the full length of the cylinder, but the compression stroke only uses about half the cylinder (The intake valve stays open halfway into the compression stroke so some of the air actually gets pushed back out!) so the compression part of the cycle is a lot shorter than the expansion part.

That's why it's very efficient (The longer expansion stroke means it can extract more energy from the combustion event), but totally gutless (Although is a 1.5 (or 1.8L) engine, it's actually only compressing a 0.7 or 0.9L engine's worth of air-fuel mix!).

The new Atkinson (Well, technically a turbo-less Miller cycle) VVTi's are very interesting tho' as you'd think they'd be undriveably gutless, yet Toyota reckon they have high torque which should be impossible on a small Atkinson/turbo-less Miller cycle engine.

What I reckon they've done is given the engine variable intake timing (Which is a natural step since they already have variable valve timings!) so that it can switch between Otto and Atkinson/Miller mode. (e.g. when power is needed, it opens the intake valves for a full cylinder of air-fuel mix, but when less power is needed it only uses half a cylinder.)