Abysmal Mpg, What Can Be Done?

[astoy]

HI EVERYONE,

Today I cleaned the EGR, changed air filter, fitted reversing sensors, reset computer, cancelled all keys and reinstated 3 master remotes, flushed radiator and renewed antifreeze and them decided to wash 95% of my car. (I always miss a bit).

Wife hasn't spotted the unwashed panel yet, but I'm sure she will.

I'll let you know how the MPG goes now, and I'm watching the oil consumption issues. If it needs attention I have the warranty bulletin printed out and will visit MrT after Christmas .

Thanks for the advice, know how and knowledge captured on this site.

Andy.

[58 Avensis T180]

I recently bought a 58 (t25) manual Avensis 2.2 D-Cat T180. I'm roughly getting about 35-37mpg around town, in the mid to high 40's when on the motorway. From what I've read on here the engine in my car uses up more diesel than the older D-4D's because of the DPF.

[astoy]

I've done a brim to brim on my second tank.

Down to 25%, I calculated it to be 43.6mpg combined.

I'm hoping to improve on that for the next tank. The last calc included half the miles done before the egr was cleaned, that and I've just done 200 motorway miles. The onboard is saying 48.5mpg, I'll be interested to see how that compared to the next brim to brim.

Still got the fuel filter on my to do list, but I'll probably postpone the oil change until after I've taken the car to Toyota about this oil consumption issue in January.

[58 Avensis T180]

I was looking into an LPG conversation with my previous car. Really did my research, even visited a place in Glasgow installed the systems. I have to say I was impressed with the technology. Took the owners car out which had the conversion done...No noticable drop in power, cant tell when it changes from diesel to LPG. Installer claims my fuel bills could be reduced by 45% if I get the conversation. My research says it's more like 40%, but still very impressive none the less. Only problem being the installation costs £2000, but if everything goes as it should you'd get that money back in savings in no time. Does anyone know of someone who has done the LPG conversion on my type of car?

[astoy]

The big risk with LPG is if it gets popular and exchequer adds on more fuel duty.

That'll eat up any chance of savings made from your £2k investment.

At 40% savings on petrol you'd need to be spending £5k on fuel before break even.

That's about 30,000 miles.

Do you have confidence that fuel duty won't be disproportionately put up on LPG in the next 2½-3 years?

Let us know how you get along!

Andy.

[t-spiritpete]

The simple answer to the lpg conversion is it can't be done on your diesel car, the compression ratio on a diesel engine is far too high for gas. Feeding hydrogen gas into the air intake and diesel through the injectors may help but this is not normally economical with an onboard hydrogen producer as this saps power from the engine using as much power as it saves. If you want an Avensis that has good mpg buy a 2.0d4d or a 2.2d4d 147bhp NOT a T180, driving a T180 like a granny will lead to all manner of problems. The best combination of power and economy would be a 2.2 147bhp chipped to 180bhp, apart from that enjoy the T180 as its meant to be driven a suffer the cost.

Best regards ..... Pete.

[astoy]

I had assumed 58 avensis T180 was talking about a petrol car.

Not heard of a diesel to lpg conversion before.

[58 Avensis T180]

Valid points Andy...

It's amazing how many people don't know about LPG, or how cheap it is compared to other fuels. The few people I have spoken to who have heard of this alternative car fuel are under the impression that only a few fuel stations throughout the country cater for it, which has put them off. The truth is there are quite a lot of petrol stations now that do cater for LPG. I don't have a crystal ball to look into the future, but have observed that LPG hasn't really caught on in Britain compared with countries, and I think it's this fact that will ensure (for now) that fuel duty for LPG will still remain low compared to diesel and petrol. The big question is does my current mileage warrant the conversation at a cost of around £2000, and the answer is no. However, if diesel prices continue to climb and I intend to keep the car for several years then it might be an option worth exploring in the future. For now I'll continue to drive sensibly and check my type pressure, etc.

[JAPCAR]

It's amazing how many people don't know about LPG, or how cheap it is compared to other fuels.

I've used LPG systems more than 15-20 years ago...carburetor and single point injection cars. It was simple and I installed and adjusted them myself. Those years it was very cheep to use LPG. Now LPG systems are more sophisticated, gas injection computer controlled systems and more expensive as well.

BTW what would happen if you install LPG system abroad, use it here and go to MOT?

[t-spiritpete]

Valid points Andy...

It's amazing how many people don't know about LPG, or how cheap it is compared to other fuels. The few people I have spoken to who have heard of this alternative car fuel are under the impression that only a few fuel stations throughout the country cater for it, which has put them off. The truth is there are quite a lot of petrol stations now that do cater for LPG. I don't have a crystal ball to look into the future, but have observed that LPG hasn't really caught on in Britain compared with countries, and I think it's this fact that will ensure (for now) that fuel duty for LPG will still remain low compared to diesel and petrol. The big question is does my current mileage warrant the conversation at a cost of around £2000, and the answer is no. However, if diesel prices continue to climb and I intend to keep the car for several years then it might be an option worth exploring in the future. For now I'll continue to drive sensibly and check my type pressure, etc.

Just to repeat myself .... you can't convert a Toyota Avensis diesel to LPG

Pete.

[JAPCAR]

Of course LPG relates to petrol engines... However I've red VVti engines are not easy to convert but not impossible.

[astoy]

Computer registers average MPG as 49.6mpg. Not bad.

To back it up I'm at just under 400miles and have just under half a tank of diesel left. 90% motorway miles.

Have to fill up soon to ensure I have good figures.

[58 Avensis T180]

The lastest LPG technology allows even diesel cars to be converted to LPG. I went to a garage in Glasgow that fitted the conversions and took the owners Mercedes Diesel for a spin which had been converted. I was well impressed. From what I remember the new italian system he used consisted of new injectors, an ECU which piggybacked the cars own engine management system and somekind of vapor unit, the proper name of the unit escapes me just now. I would recommend that anyone who is seriously considering doing this fully research it, as there are still some bad systems and installers out there.

[revband]

Can Diesel engines be converted to run on LPG?

There are currently two ways of using LPG as a fuel for a Diesel engine;

1. To truly convert the engine by reducing its compression ratio and provide it with spark ignition.

Lack of Spark Ignition

Diesel engines do not have this.

Spark ignition can be provided in several ways but they all amount to the same thing.

The most effective is to remove the cylinder head and machine spark plugholes into the places where the Diesel injectors were sited. This is only possible if there is enough 'meat' in that position. If not, the spark plug holes may have to be placed elsewhere in the combustion chamber. The existing holes for the original Diesel injectors may either be plugged or perhaps be used for direct LPG injection. Leaving the Diesel injectors in place would bring no benefit when the next factor is
taken into account......

Reduction of Compression Ratio

This must be done before the engine could be run properly on LPG or Petrol for that matter. Diesels often run at a compression ratio of roughly 16-1 (one of the reasons they are more economical) whereas Petrol and LPG engines need a ratio of around 10-1.

One way of reducing the compression ratio is to fit some form of spacer in between the cylinder head and cylinder block mating surfaces in order to reduce the compression ratio of the engine. This may present problems of gasket sealing because two head gaskets would have to be used. Another solution is to replace the original pistons for redesigned ones with different (deeper) crown depressions, addressing the compression ratio problem but now the costs are beginning to escalate,
and it must be remembered that when both of these changes (provision for spark ignition and reduction of compression ratio) have been made, the engine isn't a Diesel any longer.


Design Limits, Stresses and RPM

Although the Diesel engine is relatively slow-revving and produces its maximum torque at lower RPM than a similar Petrol version, this is not the case when it is converted to run on LPG. The revised engine has to'rev' more when running on LPG because its maximum torque has been pushed higher up the rev. band. This can bring new problems of reliability and longevity. Even if the 'top end' of a Diesel has been fully reworked, the crankshaft, bearings and connecting rods (to mention but a few components) will suffer higher stresses at increased RPM necessary when running on LPG. Mechanical breakdown may result in far less time, whilst increased
wear and reduced component life are certain. FinaIly, note that in all of the above cases the converted engine will cannot be a true Diesel or even a dual fuel engine as it will have lost its higher compression ratio and the means to inject Diesel.

Conclusion
The above factors combine (along with many others not discussed here) to make actual conversion of most Diesel engines uneconomic. It would be simpler and quicker to fit a Petrol engine.


2. To mix LPG with the existing Diesel fuel before induction (Fumigation, not Conversion)

Various attempts have been made to achieve this with varying amounts of success. Go LPG! have examined many systems and installations and after much consideration have come to this conclusion;

Overall, the Savings are Not Huge...

None of the LPG / Diesel mix systems examined have resulted in Diesel consumption being reduced by more than 25%. Those savings made must also have LPG costs (for the LPG that replaces some of the Diesel fuel consumed) subtracted from that 25% saving. This results in final savings of only the low teens of %, or thereabouts.

There are other problems to consider as well - The unmodified Diesel engine was relatively slow-revving, producing its maximum torque at lower RPM than a similar Petrol version. This is not the case when it is converted to run on Diesel and LPG mix. The revised engine has to'rev' more when running on Diesel / LPG mix because its maximum torque will have been moved higher up the rev. band. This can bring new problems of reliability and longevity. The crankshaft, bearings and connecting rods (to mention but a few components) were all designed to rev. at a lower rate. These components will suffer much higher stresses (stress increases at the square of RPM) at the increased RPM necessary to get sufficient torque when running on LPG. Mechanical breakdown may result in far less time, whilst increased wear and reduced component life are certain.

Given the low overall savings achieved (to date) and the cost of the adaption ( often equal to that of an injected Petrol engine conversion) many miles would have to be covered before any real savings are realised whilst reliability has been reduced. This does not seem to be an economically viable alternative.*

* Summer 2008 - We keep an open mind.

As world Diesel prices continue to rise sharply, there may be more economic benefit in mixing LPG with Diesel. We are still waiting to see a system that works well and comes with audited figures for reliability and the cost savings achieved. If such a system comes along, with UK LPG accreditation, we'll do some long-term evaluation before a decision is made to offer it to our customers.


Benefit becomes Burden

There are some other benefits apart from saving fuel cost.

The Diesel engine becomes quieter and more responsive when using the LPG/Diesel mix. The classic Diesel 'Knock' can be greatly reduced. The main reason for increased smoothness and reduced noise (vibration) is that the LPG element begins its combustion before the Diesel fuel does, a result of 'detonation' due to the compression ratio being so high. The engine may also get up to its optimium temperature more quickly, whilst harmful emissions like Particulates and Carbon Monoxide can be reduced. These all appear to be benefits.

Sadly, a new set of problems arise when the Driver begins to use the increased performance of an engine that wasn't designed to rev to the new, higher levels. As a result of this apparent improvement in performance, one of the best attributes of the Diesel engine (relative longevity and reliability) is dramatically reduced by the Diesel / LPG adaption.

Conclusion

On a purely fuel cost-reducing basis this adaption or fumigation system does not appear to be an attractive or useful alternative for the average Diesel motorist. That doesn't mean that the people working on these projects should stop, we hope they succeed. Perhaps their research will continue and go on to give us all a better solution.


Overall Conclusion

Above it has been shown that niether true conversion of a Diesel engine nor the mixing (Dual fuelling, Fumigation) of LPG with Diesel give economic benefits large enough to make either choice worthwhile for the average motorist.

With current LPG and Diesel technology as it stands, it would be more economical to simply remove the Diesel engine and fit a Petrol equivalent, which answers our original question -

[t-spiritpete]

Quote .... "With current LPG and Diesel technology as it stands, it would be more

economical to simply remove the Diesel engine and fit a Petrol

equivalent, which answers our original question" -

Exactly Revband .... LOL, ;)

I would have gone into all that detail but I didn't think it would be appreciated and anyway I was enjoying glass or two of Jamesons ....OH YES!

All the very best for the New Year to yourself and all the other members in the Toyota Owners Club.

Pete.

[benjyboy]

Are the days of economical diesel engines numbered? Probably not. I chose a 2.2 diesel because I tow a caravan. However if that weren't the case a 1.4 petrol would seem to be the way to go. Vw put a 1.4 petrol in the passat and tiguan. Skoda likewise offer one in the Superb. All are consideraby cheaper than their diesel equivalents and are nearly as economical, but are these to strangled by emissions technology. More to the point is the egr valve on a 2.2d4d engine causing the engine to overheat and then the hg fails.

on a more festive note, I'd rather have a bottle in front of me than a frontal labotamy.

happy new year!

[revband]

I have to confess that I cheated here and the text was copied and pasted, not my own take on the subject but it seemed appropriate and I fully agree with what is said in it.

And a very happy new year to you Pete and all other board members.

[astoy]

http://www.go-lpg.co.uk/diesel.html

Its always best to quote sources!

Thanks for finding the quote though.

AS.

[Les Taylor]

Hi,

I've just bought a 2007 2.2L d4-d Avensis, making the mistake of thinking its mpg would be something like the advertised figures.

I've just done the first tank, computer says 40.3mpg: which is awful; rim to rim says it's 35.4.

I'm speechless.

I've had the car about 3 weeks and I can't believe a diesel could have been made in 2007 that achieves 35mpg.

To rule out the obvious: Driving styles, I am driving in a similar fashion to my R-Reg Audi A4 1.9TDi, and that would get about 50mpg.

Air Filter: looks barely used, service history says 5 months old, I bought a new one and decided not to replace it after looking at the other.

Fuel Filter: Not changed since purchase, service history says 5 months.

Injectors: Injector Cleaner run through as soon as I got the car.

Does anyone else get 35mpg from an Avensis?

Can anyone suggest anything I need to do to get something almost acceptable out of this car?

What about retuning?

Has anyone remapped to get better MPG?

I really need to get this sorted soon.

Thanks

[Heidfirst]

other than quoting the op's post did you want to say something?

[58 Avensis T180]

According to my on-board computer (which I understand can be optimistic) I'm only getting 34 mpg on my 2008 2.2 d4d t180. I mainly do (sensible) urban driving with some duel carriageways thrown into the mix, very disappointing. Between the poor MPG, sticky gearbox (1st and 2nd gear), squeaky clutch pedal, and strong pull on the power steering to centre itself (especially when accelerating round corners) I think I may just end up selling the car. It's a shame as it's a well looked after, good looking car which showed lots of promise....

[Heidfirst]

I'm sure that you know by now that the lower mpg of the T180 is due to the 5th injector & of course Winter temps will have knocked a couple mpg off. Tbh diesels really aren't that great for urban use (the new Nissan London Taxi is a petrol). If you are doing mainly urban are you taking it for a good blast every so often?

The notchy 1st/2nd can be much improved by using Silkolene/Fuchs SRG 75 oil instead of the standard oil.

The squeaky clutch pedal afaik isn't a common issue ( certainly no problems when I had a T25 2.2) & I don't remember a problem with the power steering on corners (more that like my current T27 t it understeered badly with that heavy engine up front).

[58 Avensis T180]

Thanks for your input Heidfirst. Yes, I recently became aware that because the engine in my Avensis is the D-cat version, fitted with a DPF, that is gets less MPG than other 2.2 litre engines that aren't fitted with this. Unfortunately I only became aware of this fact after buying the car and joining this site. I really don't want to sell the car but unless the MPG improves (maybe by remapping the ECU. Has anyone done this??), along with the gearbox issue, I fear I will have no choice but to do so. I have already changed the gearbox oil over to Silkolene /Fuch SRG 75, and although this has helped the 1st and 2nd gear are still hard to engage most mornings when the car is started from cold. Once the Sikolene oil has heated up the gear changes are usually fine...This fully synthetic gearbox oil also seems to retain heat a lot longer than the original gearbox oil. which can only help. However, due to having no garage and living in Scotland (where we are constantly subjected to crappy cold weather), I regularly encounter the problem with sticky gears when starting the can from cold start. Can anyone advise if the 5 speed gear box experiences the same problem?? Thanks

[revband]

Unfortunately the Denso ECU has not been accesed as yet and the T180 has piezo injectors, the only possibility at the moment is a chip box which fits to the common rail and on the better ones the boost sensor, I have fitted the second option bought from Kingo of this message board, this does gave a noticable power boost above about 2000 RPM but no improvement in fuel economy.

[astoy]

My lifetime MPG is now at 42MPG, with each tank now giving me (so far): 35.4; 43.5; 49.7; 39.23mpg.

I'm ok with that. May get a box to further improve.

Oil Consumption seems to have dropped, though I'm checking it again tonight. Does anyone know what the volume difference is between the two dipstick notches?

I'm confused about this D-Cat issue, mine appears not to have a DPF from descriptions (2007 2.2L) but is there somewhere I can look to be 100% sure thats not an issue either?

Thanks,

-Andy.