Yaris Diesel - How Many Mpg?

[Stuart303]

Thanks Mike,

Sorry about the delay in replying, I was waiting for the next refill to take place to double check the figures. Had the experience during this fuel round, and the displays were showing mpg of 60.2 for the overall mileage.

I wanted to be sure this was an ACTUAL loss of fuel consumption performance, and not a fault with the display computer. But my calculated mpg for the fuel used was 60.38 (32L/435miles), and for the type of motoring I do, I would expect a minimum of 65, (hopefully more!).

There is a definite issue here, something causes the fuel economy to go through the floor, then recovers. I will try your method when next it happens.

[Celica 190]

Hi Stuart,

Bit of an update for you here. The other day mid-end journey mpg according to the up-heads display was appalling even whilst cruising. Thought the system was just having a moment and finished the journey. However driving later on the same day on the return trip home from work, from a cold start same problem. So I thought if anything I wonder whether the particular filter had anything to do with this so I left it in 4th drove 60-65 for 10 mins or so and hey presto from that point no probs, I even managed 78.5 mpg on a 55 mile trip on my way home today - the best yet! So far 1 months into ownership just over 2k mileage on the clock all going well apart from this issue, having said that don't think I've gone over 3k revs yet so I'm not really doing the particular filter any good I suppose.

Haven't done any figures just yet re actual mpg v data as long as a tank of diesel lasts me a week (560 - 600 miles) I'm happy with that!!!

Let me know how you get on Mike.

[Stuart303]

Hi Mike,

Thanks for that. It happened again on the way to work today. After stopping at a newsagents, did a bit pulling away in too high a gear - then the consumption went to the dogs again.

I noticed there is a secondary symptom - the idle speed is raised from its customary 850-900(?) to 1000 RPM.

I double checked that there were no extras running on the car - air con etc - even turned off the lights and the wipers. This persisted all the way to work - 16 miles - and returned to normal driving the last mile or so inside the works - about 2 miles from the gate to the office. During this last mile, mpg bar chart registering 75-80 mpg at 30mph flat roads.

The average for this journey was probably 40mpg (or less?). From start to finish this morning the average consumption went down from 64 to 58.5, and climbed to 59 in the last mile!

My mileage is just over 2k in 7 weeks, average for the mileage is 61.5mpg, max 65 mpg.

I am contemplating buying a diagnostic device, - they are available for about £30 - as I have no doubt that if i return it to the dealers, they will fail to find the problem. There is supposedly an OBD II socket somewhere to plug in the device, they will show fault codes for all cars regardless of manufacture.

I will keep you posted.

Stuart

[Stuart303]

Hi Mike, By the way, I found this from the AA

http://www.theaa.com/motoring_advice/fuels-and-environment/diesel-particulate-filters.html

Interesting reading.

Stuart

[Celica 190]

Hi Stuart,

Happened to me again MPG just falling off the graph!! This time I ran the car again in 4th gear around 3k revs for 10 mins, popped back upto 5th and been fine since. My theory of the particular filter being a probable cause seems to carry some weight as well, especially after reading the article you left a link too. To quote:

On cars with a very high sixth gear the engine revs may be too low to generate sufficient exhaust temperature for regeneration. Occasional harder driving in lower gears should be sufficient to burn off the soot in such cases.

With this type of DPF regeneration will be initiated by the ECU every 300 miles or so depending on vehicle use and will take 5 to 10 minutes to complete. You shouldn't notice anything other than perhaps a puff of white smoke from the exhaust when the process is completed

Typical engine revs @ 65mph = 2k in 5th, v.low revs compared to previous cars I have owned and this would only compound the situation, and my driving at higher revs for periods at a time typically once for 10 mins every 500 miles or so seems to elevate the problem.

Personally I don't think there is a fault it's just down to the type of driving I'm doing. I knew, pre purchasing this diesel about the particular side effects although with the mileage I was doing I didn't think I would experience such issues, but as the car revs are low whilst motorway cruising it appears some of the effects still appear, but a bit of driving with revs in a lower gear seem to cure it.

I don't think a diagnostic device will pick up anything just yet tbh and as there is a particular light in the instrument panel that would come on when any significant particular problem arises that would be a backup/conformation of an issue. I think were both just suffering light particular issues not enough to trigger a warning but enough to unbalance mpg readings, only a theory and I'm open to anybody else's input but this makes sense.

If you do purchase a fault reader the OBD II plug is f/o/s underdash just left of the bonnet release catch, easily accessible.

By the way my windscreen got chipped today right in the drivers view field :( Thats what happens with high motorway mileage; 2393 miles since 24/03/12.

[Stuart303]

Hi Mike,

Yes, I agree with you. I think it is down to low revs & should we say "careful" driving.

I am getting towards the end of a tank of fuel, and the average is 62.5 mpg this morning.

I have been resisting the temptation to bumble along in the gears, not using 5th below 40, & not use 6th below 60-65. This seems to keep the engine happier, and not cause the EGR system any problems.

Off on holidays Friday, roundabout route to Gatwick - Swansea - Reading - Bisley - Gatwick, so a good run various driving conditions speeds etc, should get a decent appreciation of the capabilities of the car.

A colleague in work has leant me a diagnostic device, and there are no faults evident on the car - as you surmised.

Bad news with the windscreen, had a similar experience 2 years ago - for the first time in 40 years of driving - what are they making windscreens out fo thes days???

[Stuart303]

Hi Mike,

Most recent experience with the Yaris.

Round trip to Gatwick plus 100(ish) miles to & from work, Speed on motorway <=70, elsewhere observed speed limits, a little queuing\traffic on the way home.

516.8 miles 34.21litres to fill tank to neck - average for consumption 68.57mpg, gizmo displayed 67.3 (slightly pessimistic)

On the way up the M4 had the experience of the consumption going to the dogs for 10 minutes too.

It does seem to be getting better as the car is loosening up!

I am still of the opinion that this particulate filter is a the bottom of it all.

[Stuart303]

Hello all,

If anyone is still interested, I have some more experiences to post.

Since last post, the car has continued to periodically guzzle fuel. The symptoms remain, increased idle speed, hyphens on some part of the display, "--/--". This seemed to be a cyclical event that occurred every 300 - 350 miles, once per tank, twice if unclucky.

The overall average for April-November was 68 mpg.

Then I took it for its first service.

Since then the mpg has reduce to an average of about 62. The periodic guzzling has change in frequency from about 350 miles per cycle to 200 per cycle! This now occurs TWICE in every tank of diesel.

Also, the service light (spanner) kept coming on. I took it back twice to have it reset.

I took it back a further time at the beginning of the month, sure there was something wrong. The dealers kept it for the day, and the only problem they found was that the engine oil had been over filled. I am not sure what effect this has, other than possibly to increase the pressure within the crank case.

They have asked me to do 500 miles & let them know how it has gone.

I am close to the 500 mile mark now, and though there is some small improvement in the mpg, it is still below the 68 mpg average I have previously experienced. AND the guzzling cycle still occurs EVERY 200 miles.

[Madasafish]

It's winter. a 10% increase in consumption is normal. in every car.

[Stuart303]

Thanks Michael,

I understand about winter fuel usage.

What's giving me grief is the cyclic guzzling of diesel, now reduced to every 200 miles.

Have you come across this phenomenon yourself?

[Madasafish]

Stuart

My Yaris diesel is pre these diabolical devices.. so I am afraid I am dumb and ignorant - as always...

[Celica 190]

Thanks Michael,

I understand about winter fuel usage.

What's giving me grief is the cyclic guzzling of diesel, now reduced to every 200 miles.

Have you come across this phenomenon yourself?

Hi Stuart,

Wowza you seem to be experiencing some issues there, when comparing it to my own situation:

I'm currently still doing 550 (or just over) miles per week - 95% motorway. This is a tank of fuel (Sometimes to 0 on the trip!), mpg isn't as great as in summer weather (Ordinarily 75mpg, best 78.9 on the same trip)), but this week I brimmed the tank with 36l of diesel and on a random cold day this week on way to work - 55 miles, the temp was 3 degrees, and I still managed to get 71mpg, average speed say 65mph, using only up to 5th gear and just driving normally through the gears.

The clock has just clicked over 23K in 11 or so months. and it's been serviced twice with no adverse affects.

Still every week the mpg will do some kind of self-calibrating option reducing mpg to around 30-40 mpg for 10 minutes then normal service is resumed for another week. I questioned this at the dealer on my last service and the said that this was usual and a self checking/calibrating function at that.

The worst case of fuel performance I have experienced was only getting 510 miles to a tank, but this is still well above what you've been experiencing. City driving will certainly drive down the mpg though! But no guzzling issues have been experienced.

[Stuart303]

Thanks for the reply Mike,

My daily round trip is 32 miles, 6 of them on the M4, the rest on A roads (with A LOT of traffic lights!) so I would expect it to be worse than100% Motorway driving. The time I travel helps though, early out & back so light traffic.

Been back to the dealers today, and they still can't tell me what is going on. The service manager thinks it is the system doing some sort "self cleaning", but is stumped because the diagnostics show nothing.

At 300 mile interval, it is a nuisance, at 200 it is a complete pain. The potential without this feature would be 70+ mpg, just filled it today and the average for the tank was 61.8 over 499 miles.

The guy has promised to query the Toyota technical department, but has no evidence of anyone else complaining of this problem.

I have a feeling they don't believe me, so I offered to try to deliver the car to them when it is in this mode (if only to prove I am not imagining it). This ought to be possible; I think I can predict when it will happen by now!

[Sarahnya]

I get around 62 MPG on the motorway, usually stick to a steady 70 mph. Around town I get a good 55+ though so it's pretty good :)

[Stuart303]

Finally!

After many visits & complaints & checks, the dealership & Toyota think they have cured my problem!

To recap, this has been an issue ever since the car was new -
periodic guzzling of fuel for a full 15 minute period, roughly once per tank of fuel (or 300 – 350 miles). A “regen” cycle.

After a service last November, the service light kept coming on, and I visited the dealership several times to have this reset. Also, from this point onwards over the next 6 months (November to May) , the frequency of “regens” increased from once per tank to twice, three and finally four times per tank of fuel.

In February, the car went back to the dealership to have the service light issue investigated. They checked everything they could think of, and every reading was within normal bounds, DPF saturation at 46% (a clue perhaps?? A friend of mile told me that even 5 year old BMW’s don’t get that high a reading.)

They found that there was more oil in the sump than thereshould have been. We both assumed they had overfilled the sump during the service – I am now sure this was an incorrect assumption on both our parts. I was asked to drive the car for 500 miles & return to have it checked. I did so, and all seemed well, except that the guzzling of fuel continued to get worse.

About three weeks ago, the service light came on again.
Before doing anything else, I dipped the oil. Sure enough, there was about ¼” (6mm) of oil showing over the “full” mark on the dipstick. This could not be excess engine oil.

It turns out it was diesel fuel finding its way into the sump.

I contacted the dealers, took it back and they asked me to book it in for more investigation and that they would need to keep it for a couple of days. They kept it from the 7^th to the 13^th of May. Fortunately, they provided me with a courtesy car!

During this time they checked everything they possibly could, injectors, fuel pump filters, turbo etc. All were fine.

What they did discover, was that during these "regen" cycles, although extra diesel was being squirted into the engine, it was NOT burning and NOT cleaning out the the DPF, perhaps hence the 46% saturation.

The EMU (or ECU??) was also checked, and they found that the software installed on it was for a 2011 engine. Mine is a 2012.

The DPF has had a “forced regen”, so the saturation level is now zero. They have also updated the software installed on the EMU to the 2012 level, and I am assured that the “regen” frequency will be much extended, and the event of much less duration, and barely noticeable.

I hope so!

[Cyker]

Yikes!

Did they find out why the regen diesel wasn't burning? I assume it was injecting when the exhaust wasn't hot enough or something?

Anyway, hope that they fixed it!

Thanks for reporting back too; Hopefully this will help out anyone else who runs into this problem!

Maybe you should treat it to some V-Power diesel now and then! (Only half-joking; It ignites slightly easier than normal diesel so hopefully won't just flood the dpf matrix!)

[Stuart303]

Thanks Cyker,

I hope they have fixed it too.

The major frustration here for me is the fact that I complained to the dealership right from the first time id did "regen". They failed to understand what I was telling them. It was some months AFTER I found out about "regens" BEFORE they mentioned it.

I have since had a call from a nice lady at Toyota Customer Care to ask if all was OK now. I explained to her that the fault had been found, and hopefully fixed, and I suppose it was a bit of a difficult one to find.

I also pointed out that I was hoping that running the car for potentially 15 months, with diesel fuel getting in amongst the sump oil would not provide problematic in the future.

I have tried V-Power on and off and it did seem to provide more mpg than regular diesel - doesn't seem to be any more or less expensive, cost more = more mpg?

[Steve_75]

I thought I'd join up and add my experiences to this. Bought my 1.4D new in March. Been very good (just had a bit of wind noise on the drivers door which - after I'd found the source because the dealer couldn't - was fixed).

Getting around 60-63mpg out of it on a good mix of town and longer runs. Best so far is 69mpg on a run back from South Wales. (MPGs from the computer but I've checked them over a tank against brim to brim calculations a few times and its usually within a couple of tenths).

I have the same issue with the regen that's been described here. Seems to be about every 350 miles (the last two were at 1890 and 2237 miles). I quite often drive with the 'Car' info screen on the Touch and I can be cruising gently, seeing the bar graph showing around 75mpg and then the regen starts and I struggle to get it over about 40mpg! On a run to near Daventry and back yesterday, the average mpg was showing 58.7 when I left home, up to 61.3 when I got there but it went into regen just after I left. Lasted about 15-20 mins. By the time it was finished, I was back down to 59.3 (over about 10 miles of driving gently!).

If it happens when I'm stuck in traffic, the stink of the soot being burned off is horrendous!

I'd be interested to know if Stuart303's car has stopped the regens since its been worked on. Is there any way of checking how clogged the DPF is or does that require the dealer to plug a computer in?

I wouldn't be surprised if some of the newer cars had issues due to them being moved round short distances for shipping and at the dealer. MIne was a 'stock' car so I guess came from somewhere else in the country. My previous car was a 2012 Verso 2.0D and the only time that went into regen mode was after xmas and new year where it wasn't used much and what use it did see was short journeys. It was on about 10 or 11k miles by then. That one was on the ship when I ordered it so came straight to the dealer.

If I could stop this regular regen cycle, the car would be fantastic.

[Stuart303]

No it isn't fixed!!!!!!!!!

What Steve posted above seems to be normal behaviour for the Yaris. I don't believe it can be stopped, it is required to clean out the DPF. Although Toyota don't seem to want to publish this.

Interesting to see Steve's experience with a door seal too. My front windows have never clear rain\mist when you lower\raise them to clear rain\mist! The build quality doesn't seem so good on this model as my previous Auris

The once per 350 miles regen would be a godsend to me at the moment!

Since the garage had it last (for a week) the average between regens is slightly over 100 miles, 4 times per tank.

I have just checked the oil level again today, and it has increased to 1/4" over the full level. So their claims of having fixed it with a software update do not hold water.

I am sure this is something that is "sick" with my particular car - but they can't find out what.

Been in touch with the garage, & they have asked me to bring it back again today to have the oil replaced.

I will post more as things move on.

[Steve_75]

I might give my dealer a call at some point to find out what their take on it is.

BTW, the seal I had an issue with was actually at the top of the quarter light where the vertical post met the angle at the top. Seals didn't quite meet properly so there was a 1-2mm gap. Caused quite a lot of whistling for something that was only slightly out. Dealer service is pretty good though and replaced the seals without question. Most cars I've had in the last few years don't really clear rain and mist when you lower/raise the windows.

It's a pity there aren't that many Yaris diesels out there to get more experiences from to confirm whether this is a known issue or if a handful of us are unlucky.

If your oil level is increasing like that, then surely it could damage the engine eventually, especially if left unchecked between services. Plus I don't imagine diesel is as good a lubricator as the proper oil! Would be interesting to see what Toyota say about that - I know it's recommended that we check oil levels regularly in case they drop but what are you supposed to do if it keeps going up? It's not like most people will have the facility to drain some off (which would result in the proportion of diesel in the oil increasing) and I can't imagine Toyota will pay for regular oil changes at the dealer!

[Steve_75]

Quick update. Called my dealer and explained the problem to them. Mentioned what had been said on here and they said that rather than assuming its a DPF regen, they'd like to start from scratch so have booked it in for a couple of days next week (which hopefully will coincide with the next set of symptoms!).

He said he wouldn't expect to have any DPF regens until 50 or 60,000 miles with normal driving.

Will be interesting to see if they can find anything.

[Cyker]

What??? 50-60,000 miles before a regen is needed!? Whoever you spoke to either didn't understand what you mean or doesn't know what they're talking about!

Under normal circumstances, all modern diesel cars with DPF's will need some sort of regen cycle every 300-600 miles depending on how they're driven! No way could a DPF hold 60,000 miles worth of soot without blocking off the whole exhaust!

Even in Hong Kong, where self-regenerating DPFs are less common (Mainly because they'd almost never go fast enough to heat up the DPF sufficiently for the regen cycle to work!), the disposable filter usually has to be changed much more regularly than that!

It may be the guy you spoke to worked for another manufacturer at some point, as apparently the self-regenerating DPFs in some vehicles need to be replaced at 75-100,000 miles as they get full of ash which can't be burnt off, but the Toyota ones are supposed to be for the life of the car!

Yeesh, it makes me glad my Mk1 doesn't have one of these things!

Oh, and re the V-Power diesel, glad you did get some better mpg out of it - I usually get a bit worse unless I'm doing lots of motorway driving!!

The only reason I suggested it is that V-Power diesel burns easier than normal diesel, so if the problem is the exhaust isn't getting hot enough when the regen triggers, the V-Power may tip the balance enough to ignite and burn off the soot.

If they cleaned it for you and it's still doing it tho', I think there is another problem; Maybe the DPF or fuel injector is so caked up with crap that it just plain isn't working!

[Steve_75]

I thought it was odd to go that far!

Starting to think that a regular regen is 'normal' (though Stuart303, every 100 miles probably isn't) - was searching online and found a forum discussing Hyundai i30s doing the same thing. Maybe my 2.0d Verso did do the same kind of cycle but I didn't notice it as it didn't have such an impact on economy (and I never used the instantaneous mpg display). The one time I mentioned noticing it with the Verso was when it had been used exclusively for short journeys and then the main symptom was a 1200rpm idle.

Seeing as all the dealer is likely to do is stick it on the computer and drive round a bit to see if it does it while they have it, I might cancel the booking with them and experiment a bit myself. Maybe try a tank or 3 of v-power or similar or a couple of tanks where I'm not driving economically, changing up early, light throttle, low revs etc and have some fun instead!

[Cyker]

Yeah, it's really ironic that these environmental crap devices actually require you to waste fuel to stop them breaking!

But yeah, the regen thing is normal; I didn't realise there were two types of regen - Apparently, if you are driving long distances or high RPM for a long time, you get something called a passive regen where the exhaust is hot enough to burn off some of the soot. Other times, when the exhaust isn't hot enough, there is an active regen which injects fuel into the exhaust to try and raise the temps so the soot starts to burn.

It's all quite stupid really, especially given that diesel engines have EGR valves which REDUCE the combustion temperature!

V-Power diesel supposedly burns more readily and cleaner so in theory it should reduce the frequency of DPF regenerations and help it burn off the soot easier when it does regenerate.

Sadly, in real life it's not so cut and dried - For some people, it seems to work well, but others have reported less success so 'your mileage may vary' as they say

(I do know I see a lot less soot when revving up my D4D with V-Power vs Sainsburys, but it hasn't stopped the soot buildup in my EGR throttle body significantly :( )

[Stuart303]

Oil replaced yesterday again.

Service manager on holiday till Thursday, must wait for him to return for further action.#

On the fuel front, the last fill was of Esso premium (or whatever the call the good stuff), and it certainly seems to be more economical. Current average near end of tank 66.4, this is better tan of late.

More as it develops.