Fuel Economy Questions!! Cheapskate alert

[andy.cowman]

Hi all

I have a 200tdi Defender 90 with 100000 miles on the clock. The fuel pump is only a few years old and I have the drop in replacement AliSport intercooler.

I started thinking about 'other' fuels when I was faced with a commute. That hasn't happened but I realised I could drop the running costs of my defender quite a bit. From reading all of the internet I have the following thoughts on which I would like some discussion!

The Bosch fuel pump is happy with SVO, although the seals may wear quicker. This can be offset by mixing diesel and rapeseed oil from the cash and carry.

Pure oil won't burn properly in the 200tdi engine therefore I should use a mix

People seem confident on 50:50 in the tank with out the requirement for modification to anything.

It is illegal unless I inform HRMC and pay 27p a litre on what I chuck in the tank.

So who uses it? Who uses used oil? Who has told the Gov about it???

Cheers

Andy

[Howitzer]

I use Rapeseed oil which costs me 76p a litre.

I have run with a mixture up to 50/50 but it felt its best with a 30/70 mix of veg oil and diesel.

1 in every 10 tanks I run a 100% diesel mix, i've not heard many do this but it gives the chance for any deposits to burn off if they are infact developing.

During the winter i'll not run any veg oil due to the cold weather thickening up the mixture too much.

I haven't told anyone about it but have kept all of my receipts for the oil incase I am ever stopped.

I have no qualms in using it, it's a little bit quieter on the stuff and apart from a few diesel filters when using my first tank, it has been totally faultless.

Dave!

[Aragorn]

It was my understanding that unless you were getting the oil for nowt (ie used) and processing it into proper biodiesel, there wasnt really much to be saved any more, as the price of veg oil has risen so much, especially when your running 50:50, so the savings are instantly halved anyway.

You dont have to pay tax on the fuel if your using less than 2500litres a year. If your over that, and using real biodiesel, the charge is 27p however SVO is classed as a fuel substitute, and gathers the full rate of 47p just like diesel.

[andy.cowman]

So if I walked into Sainsburys and bought 12 litres and then poured it in the tank and filled the rest up with derv I would be ok legally? Right up until I went past 2500 litres?

It is partly an experiment to!

[Puffernutter]

My 110 has been converted to a dual tank and run on SVO for the last 2 years. I pay 86p a litre for Rapeseed Oil from Macros (I don't use soya). If you use less that 2500 litres a year then there is no duty.

I see you live in Bath, I live in Trowbridge, come across and have a chat sometime.

Cheers

Peter

[nicks90]

keep receipts of all the veg oil you use - you are allowed up to 2500 liters a year before HMRC get involved and sting you for fuel duty,

i too run veg oil and diesel mix, during the summer in very warms weeks i will go up to 70/30 veg / diesel. Rest of the spring summer and autumn i run 50/50 mix. When it starts getting chilly and consistently in the single figure temperatures - i revert back to pure diesel.

i get my veg oil for about 71p per litre, so when mixed 50/50 this equates to my fuel costing approx 95p/l

thats 20p/l saving....... well worth doing.

Even after doing this for several years - i still find it quite weird standing on my drive pouring a 20l barrel of KTC veg oil into the fuel tank.

[Retroanaconda]

I'm personally not convinced, unless you can access it very cheaply it doesn't seem to amount to much.

Using the figure above of a 20p/l saving, I would save about £15 a month....I'm not sure it's worth the hassle for that saving. Obviously if you did more miles, or had access to very cheap oil then it could become worthwhile, but my 90 does 30mpg and I'm happy enough with that on normal diesel!

[reb78]

Can you use any veg oil? i.e. you can buy sunflower, rape seed, corn, soybean, veg oil (not sure if that is a mix of several) etc...... - will they all produce the same results or do you have to be careful which you buy? Do you have to have the injectors overhauled more regulary because they gum up even if you limit it to say a 50:50 mix max in the summer?

[Puffernutter]

I was advised NOT to use any soya derivate. I only use rapeseed oil.

The higher the concentration of oil, the more risk of long term damage to the engine. I use 100% rapeseed oil, but always start and finish on diesel, so there is no veggie in the bores (or not much anyway) when I switch off.

Lucas injector pumps cannot cope with any veggie oil (well not for long anyway )

Bosch pumps are far more hardy, but again, the higher the concentration of oil, the more the need to have a heat exchanger to heat the oil and make it run more freely, reducing the load on fuel pumps and injector pumps.

Cheers

Peter

[Diablo]

There's also a good chance you'll need to change your injectors early on [first year or so], particularly if you have an older car.

Personally I would never put veg oil in the tank without a proper twin tank system. I don't want to have a coked up engine, hence I have 2 fuel tanks.

[Puffernutter]

Why is that? Does oil have a bad effect?

I have noticed more smoke recently, could that be the reason?

I have a two tank system.

Cheers

Peter

[andy.cowman]

Well it sounds like it might be worth a try with the thought of heading towards using UVO when I have some space to keep it.

To start with I will try a mix of diesel to rapeseed oil in the tank and see how I get on with it - not overly concerned about the saving until I know if I am happy running on it. Will pop in Sainsburys and get some oil to go in with the diesel!

Peter - I am currently living in Datchet but will be moving back to Wiltshire in Decemeber. Looking to rent around the Market Lavington / Westbury area and change job to any firm looking for MI / BI analysts and developers! (who likes my subtle hint?!)

[G_Cam]

Hi All

In my 200tdi I use a 50:50 Veg/Diesel mix in summer

100% Diesel in the winter

No ill effects to date (3 years and 30k miles later).

I tip it into the tank and run every 10th tank full on 100% Diesel.

The only disadvantage is the number of questions you get asked when you tip the Tesco veg oil into the tank in the Tesco car park

[nicks90]

There's also a good chance you'll need to change your injectors early on [first year or so], particularly if you have an older car.

Personally I would never put veg oil in the tank without a proper twin tank system. I don't want to have a coked up engine, hence I have 2 fuel tanks.

Why?

there is a lot of missinformation out there about veg oil. Veg oil (we're talking about runny oils here, not palm oil) all have a very simillar viscosity to diesel when above 50C in temp.

Once the veg oil is compressed to VERY high pressures by the injectors and squirted into the bores - trust me, it will be HOT. That means it has very simillar viscosity, very simillar atomisation and very simillar flash points to regular diesel. Search on t'interweb and you will find the flame temps and calorific values of most veg oil is simillar to standard EU spec diesel. So as far as combustion goes, as long as your injectors have a good spray pattern you will not do any harm to your engine. Ring gumming, carbon build up on the nozzles, lots of smoke etc - they are all symptoms of bad injectors and you will have simillar problems even if running on diesel.

What can cause a problem when using veg oil is that before the injectors its cold. Cold oil is thicker than diesel and therefore can put more strain on your fuel pump and injection pump. If your injection pump is weak then you may find when its cold you notice a performance loss or maybe even some uneven running as it will struggle to get the pressure right in the high pressure pipes feeding the injectors. However, the engine heats up the injection pump very quickly and this acts like a very good fuel heat exchanger, so this usually only manifests itself when the engine is cold.

i started using veg oil at 120k miles, i am now on 158k miles and still havent touched the injectors. Not had a blocked fuel filter either. Not had a failed fuel pump. Not had a leaking injection pump. Engine doesnt smoke.

Be sensible and not use super thick veg oil at high mix ratios when its cold and you will be fine.

[andy.cowman]

Lots of good info here from people who are doing it, I have a full tank of diesel at the moment and I plan to let it run down a bit (do about 85 miles) then top up using rapeseed oil from the super market and will see what happens.

If temperature at start up is a problem what options are there? could wire up a spare glowplu to heat the fuel? Are there heat exchangers to preheat the fuel?

Cheers

[reb78]

Are there heat exchangers to preheat the fuel?

Well, there are, but they need a warm engine to work since they run off of the coolant, which is why a dual tank system makes so much sense really that lets you start and purge on pure diesel at the end. Not sure if anything exists wrt heated fuel filters - seem to recall someone mentioning one from a peugeot once, but again, unless this is electric in some way, it will only be effective once the engine has warmed up. My tdi takes a while to warm up in mild weather, it takes forever to warm up in the cold! (I know, i should check the thermostat!)

[Puffernutter]

There are two methods of doing it. One is through a heat excahnger using the car hot water circuit (normally off the heater matrix), the second is a design using glowplugs.

However, both of these will require a two tank system to start and then purge at the end.

My problem (110 200Tdi) is the run of fuel pipe from the tank to the heat exchanger down the length of the car! Although once it has changed the spill pipes will feed hot oil back into the tank, so after a while the whole tank will heat up.

I used my two tank system through the whole of last winter, I just got a loss of performance when it first changed over and the cold "slug" of oil had to work through from the heat exchanger and through the injector pump.

Cheers

Peter

[Adam001]

Grant has pointed me in this direction

I too have a 200tdi defender and I run on 100% vegetable oil, I have a twin tank system with a coolant heated veg filter and a flat plate heat exchanger in a closed loop, so I start on diesel, the diesel heats the pumps and injectors then I switch over to veg oil, nice and simple

Cost me DIY about £230 about 4 Months ago and I have already saved about that.

I do have a ton of photos if it's any help

But if you want a simple method then you can just mix it, but you won't save as much

[reb78]

I do have a ton of photos if it's any help

Do us a tech archive thread on it...........

[andy.cowman]

Grant has pointed me in this direction

Hi Adam!

I spoke to Grant last night, he says you are 'the man' for veggie oil! So How did you do it? Having just done 500 miles in the landy this weekend I am upset that I only averaged 25mpg (i say upset, more like broke) so i want to get on and convert.

My next questions are about sourcing the oil, I will be moving down to the Wiltshire area in December - anywhere from Devizes to Norton St Philip - so where do people get their oil? Peter this is mostly aimed at you!! Are you cleaning up your own waste oil or picking up new on the cheap? Adam what do you use?

Cheers!

Andy

[Puffernutter]

Andy,

I buy new oil that works out at about 86p/litre from Makros. I only buy rapeseed oil and I have heard that soya can be more harmful.

I have thought about processing (I have been offered a processing set up for £900) that will give me oil at about 10 or 12p a litre (assuming that you get it for nothing) but I can't guarantee usage, so I'm loathe to commit to collect x litres from a local chippy and end up with the garden swimming in oil!

Cheers

Peter

[Adam001]

I'll do a tech archive later on how I went about doing it with a few diagrams even

My veggie system works on the normal twin tank method, I have 2 filters, one for diesel one for veg (coolant heated) which feed into a 3 way solenoid valve which leads to the lift pump then via a coolant heat exchanger and a small inline filter (safety) into the injection pump. The return is fed to another 3 way solenoid which either sends fuel back to the veg tank (for quick purging of fuel, or back into the coolant heat exchanger to form a closed loop (less fluid then has to feed through the filters etc) there a benefits to different types of systems, but this works for me.

Currently I am buying sunflower from tesco at 80ppl but hoping to get on and source WVO or get SVO from costco or similar. But for me, I don't know about anyone else but since I converted my fuel economy has gone up massively and by cost I get the equivalent of near 50mpg on a run. (which obviously is now negated because I drive faster )

[Puffernutter]

I have also have a twin tank system:

Main tank (veggie) > heat exchanger > (from cab heater circuit) filter > 6 port switch > injector pump.

The slight disadvantage with using a 6 port (rather than two 3 ports) is that immediately on switching the spill will feed to the same take as is feeding, so I get a bit of diesel in my veggie tank, but also a bit of veggie in my diesel tank!

I have a thermal switch (from RS) on top of the heat exchanger and when the magic temeperature is reached (70degC I chose), my system switches automatically. I have a light on the dash that goes from red (diesel) to green (SVO) so I know it has switched. Before journey's end I have a switch on the console that puts it back to diesel to purge. When I stop and remove the ignition key, a buzzer sounds, reminding me to re-toggle the switch ready for next time.

I also have a couple of hidden switches that can force it to SVO or to diesel if needsbe, in case I have problems with either tank.

Cheers

Peter

[Disty]

I'm suprised nobody has mentioned homebrew biodeisel yet?

Having done my own research I've come to the conclusion that my best option is to convert the SVO to Biodeisel using methonal and sodium hydroxide (aka caustic soda). This can then go straight into your tank no worries. with 12% of the mixture being methanol, you'd need to buy it in bulk to get a decent price. (my latest quote was "£17.00 per 25L drum (based on a load of 4 drums)" making it 68p a litre- pretty cheap)

You can get 100% rapeseed, 20 litres for £15.50 from my local chinese supermarket (78p per litre) and convert it to biodeisel very easily. Only difficult part is heating up large volumes I would say.

[andy.cowman]

I had no idea the MPG increase from burning Rapeseed would be so much, i am even more keen now!! What twin tanks do you run? I have seen that a td5 tank would fit between the rear chassis members but is there a better option?

Rapeseed is the way - really need to go and buy some and see what happens!

Adam a technical article would be much appeciated, it will help Grant help me

Peter - yes the storage and work involved with the WVO is something that makes me hesitate. If Rapeseed can be bought for less than 80ppl and makes you go a lot further than the same volume of diesel then it seems well worth it.