Hello,

I have a 2004 Octavia classic, 1.9 TDI 90bhp ALH engine.

263k miles.

Cambelt and water pump done recently (january 2013), engine running well with no fault codes apart from one for the anti-shudder valve on the EGR because it is hanging off. New starter motor too. Starts very well. Oil and filter changed in February 2013. Fuel filter changed December 2012.

I do about 700 miles a week. Same commute each day (47 miles each way) and some motorway runs. Genuine 57-59 brim to brim MPG.

I have been researching using SVO (straight veg oil) and WVO (waste veg oil) in this car for a while. I ran my Audi 80 TDI on it for a while too.

Here are my findings:

I ran approx 250 litres of biodiesel in the past few months (approx 2900 miles on biodiesel), in various proportions of bio / diesel. Proper biodiesel from a commercial supplier in Bristol. No problems, except a drop in fuel economy.52-53mpg on bio. THis meant that the MPG is 89% of the diesel MPG, at 80% of the price (£1.10 a litre tax paid vs £1.39 a litre of diesel). So slightly cheaper overall. I didn't get any fault codes or problems with the "fuel filter blocking after 1000 miles as the biodiesel cleans out your fuel lines / tank".

I also ran a mix of biodiesel / SVO (tesco sunflower and rapeseed oil) in varying proportions. When it was 70% bio and 30% SVO, it ran fine.

Then I put in 70% SVO with 30% biodiesel.

It ran like a bag of ****e.

Very hard to start.

Under hard acceleration it would suffer from fuel starvation as if the fuel filter was blocked.

It also caused the engine management light to come on. I carried my laptop with me so I could plug in VAG COM but it only did it on 3 journeys (150 miles). I suspect it was something to do with the nozzles on the VNT turbo sticking.

So, after 400 miles I put in normal diesel, and it has been fine ever since.

I don't know how people can run 100%SVO or 100% WVO, as it caused me big problems.

I also don't know why people think that "the fuel filter clogs with biodiesel as it is cleaning out years of crap in your lines / tank", when I ran bio for 3000 miles it was fine, the SVO caused the "filter blockage problems" which disappeared when I switched back to diesel. If the filter was genuinely blocked, then putting diesel back through it would not cause it to "unblock".

I decided the cost of running SVO at £0.85 per litre vs any big repair bills were not worth the hassle.

Just my thoughts and findings.

Right, i'm not a mechanic, i have no mechanical training, beyond paying atttention when things are being done to my cars over the years.

but i would imagine purely from purchasing veg oil for use in the kitchen, that it being a lot thicker than diesel

that the fuel pump and filter are going to need to work alot harder to keep fuel flowing at the correct rate, if your running on majority SVO or WVO?

thats based purely on the whole if its thicker it runs slower, esp thru a filter membrane,

and an oil is more compressible than a thinner liquid, any increase in demand, hard acceleration,

is going to take a cuple of seconds for the increased flow rate to make it from the fuel pump to the engine, as the liquid compresses first under the higher pump rate?

I was also told by a mechanic friend that a lot of the Bio diesels have too high an Ethanol content ( as do some regular diesels now) to boost the fuel efficiency.

which in one sense is great, better mpg, but on older engines it corrodes the piping faster which leads to more problems and costs.

ive not heard of the "Filter Blockage Problem" but i more say its due to the fuel not moving fast enough to the engine, ie starvation as you described.

I found low percentages of SVO made no difference. High percentages resulted in exactly what you say.

Sure someone on here said they use a lift pump with SVO to overcome these problems. Don't remember where it is though.

It depends on so many variables. I think I've done something like 25,000 miles on veg in the last two years in both a Rover 45 and a Shogun 2.8. I always used brand new veg cubies straight from Makro (whatever was cheapest that week, always either KTC or Pride). I used to mix 70/30 oil to diesel, but went to 90/10 oil to unleaded petrol. I only ever had one problem, and that was with the Shogun. On the run back down from Scotland it started lacking power and couldn't pull the **** off a chocolate mouse until I ragged in about 30 litres of diesel. Turned out to be a loose fuel line at the heat exchanger, coupled with the miserable weather over the GP weekend last year causing the oil to thicken and pull in air.

The quality of the bio is also critical. Badly made bio often contains too much ethanol (rots the fuel lines and seals, and is very wasteful - real bio people recover every last drop possible from their brews as it's reusable) and causes bad running.

Ive been looking into this after a mate mentioned it for his diesel and from what you say i say you need to heat the svo to help it run through fuel lines easier

I ran a Mitsubishi Pajero on 100% veg oil, it was bought from a guy in Knowsley, tax paid, there was the odd occasion I ran straight mazola corn oil from asda.

As for the PD or CR engines, I understand that the high pressures in the system are not suited to higher viscosity liquids.

I believe you can use kerosene though with an addition of 40 spec hydraulic oil, this is cheap and illegal as no tax is paid. It does work very well.

Ive been looking into this after a mate mentioned it for his diesel and from what you say i say you need to heat the svo to help it run through fuel lines easier

I was running a heat exchanger I got from eBay that used to plumb into the heater circuit. It was basically a heat exchanger from a combi boiler.

Is it worth adding millers ecomax in to boost the cetane level and add detergent? adds 2p per litre to the cost

I dont know if the boster would have any effect if the fuel isnt able to change flow rates fast enough to avoid the slow throttle response?

I ran an old Merc300d on SVO 100% - did about 60k with no problems (until the price rose in 2008 from 45ppl to 130ppl) - then decided on a newer car on autogas. The merc struggled to start if the temperature was below freezing - it needed a few attempts with the ignition key to re-energise the glow plugs. I think SVO is more suited to older (indirect) low pressure diesels, and the PD/common rail stuff is doesn't like the higher viscosity of the fuel

Thanks for the thoughts and comments.

The engine is not pumpe duse (PD) or common rail (CR).

As I need it for my livelihood I will stick to diesel. Might get some more biodiesel for the slight price benefit.

I used to use Nitrox Hot Shot cetane boster, it actually seemed to make things worse to be honest. the Rover never needed it, the Shogun just hated the veg oil full stop. Some vehicles just do, no rhyme nor reason.

The engine is not pumpe duse (PD) or common rail (CR).

As I need it for my livelihood I will stick to diesel. Might get some more biodiesel for the slight price benefit.

If running the bio, just make sure to keep the hoses etc checked for being eaten by it....

Hello , I'm new to this Forum. 

 

I have just started making my own BioDiesel from Veg Oil. 

The Oil has been thoroughly filtered and looks lovely and clear - PRE PROCESS. 

We use a standard Batch Method - and bubble off as much moisture as possible - as well as extracting as much Ethanol off as possible - we condense it and use it again. 

 

I will be filling up my first tank 50 - 50 Bio D/Petrol D tomorrow. 

I have a spare fuel filter in the boot ready for the change over. 

 

I will keep you informed as to the result. 

 

I have heard "stories" of a fungus that can grow in the BioD that can clog up the fuel lines. If the vehicle is not driven enough*.. ..does anyone else know more about this. A quick Internet search has yielded nothing. 

 

*we drive ours only once a week for about 2-3hrs. 

Octavia estate 1.9 Tdi AGR,ran my fist T reg for 10k on new veg oil then 70k on filtered used oil before I scrapped it,looking back the failure of my MAF caused the egr valve to allow too much rubbissh back and blocked the air intake..2nd Y reg Octavia is still running on used veg oil now done 45k without a hicup.I have a twin tank system so startup diesel tank in boot 2 3 way walves(one for fuel select one for purging) a 2 pole a three way switch on dash to select diesel,veg or purge.Heated fuel filter to heat veg and then a small heat exchanger to heat before pump..bingo saved £1500 last year alone on fuel.I would say all parts max £250 inc 2nd tank(tank can be as small as 20 litres)fit yourself over a steadt weekend.If you want to view mine I can give you 1 hour.

Thin the veg oil down if you aren't heating.