Veg oil/bio deisel - The final word

I ran my 200k mile mk3 golf on 100% veg for about 1500 miles. It drove fine but was a bit more clacky when cold. however the veg oil made my diesel pump leak from the head seal - Apparently they all leak a bit oncee they have some miles under their belt, but diesel evaporates when it runs down the block so you don't notice. Veg oil makes the leak worse due to higher pressure and presumably affecting the seal, so it turned a barely noticeable "slight wiff" into a real issue leaving big puddles under the vehicle when parked and affecting economy.

I just got unlucky on that front, but if it wasn't for that I would have probably got bored of running on veg not long after (I put a new pump on and just switched back to dino)

On top of that, getting the stuff into the vehicle was a pain in the backside (even with the best funnel and perfect execution, you always end up with sploshes and dribbles all over the place), as was disposing of the containers since the local tip wouldn't take any more than one at a time, and my wheelie bin is always full.

To start off with I was all for it, I could get veg for just under £1 a liter from costco, but in the end the hassle of driving to get it, pouring it all down the side of the car when trying to funnel it in and the risk of upsetting my diesel pump again pretty much stopped it being worth the hassle to save about £18 every 500 miles.


If you have a rough old beast of a car, work at some kind of filthy mechanical place who have a big bin you can chuck any old stuff in and a greasy carpark you can slosh veg oil all over, and you pass costco on the way to work then it's a no brainer. Otherwise it's a lot like spending hours on the net to find the garage 15 miles away selling diesel 2p cheaper, and then getting a load all over your hands when filling up.

In the summer you can run on 100% veg but in the winter you will want a mix of about 50% veg and 50% derv to help it start when it's cold.

I've done tens of thousands of miles running on veg oil and diesel mix in a variety vehicles. Only problem I ever had was with a Peugeot 205 that had already done over 200,000 miles with the CAV injector pump leaking and was a sub £5 fix for a new seal.
This was when veg oil could be bought for under 50p litre. Now veg oil is only a few pence less than diesel from supermarkets I wouldn't bother. Ease off your right foot and drive carefully will get better mpg that far outweighs the few pence difference between veg oil and diesel.

Paul H

And this is not entirely true...

SVO (straight vegetable oil) or WVO (waste vegetable oil) has a different viscosity than diesel (or biodiesel/RME at that). SVO/WVO is less liquid, so to speak. The injection equipment is mechanical and injection timing etc. is based upon the viscosity of the liquid runing through the injection lines, the liquid's pressure to pop open the injection nozzles etc. Many people notice that the engine runs quieter on SVO/WVO. Which is a symptom of just that...

If you alter the viscosity of the fuel, which you do so by using SVO/WVO, you need to tweak the injection equipment in accordance. Advanced timing, and higher pop-pressure for the injector nozzles is required to regain efficient burning of the fuel and regular operation of the engine. The engine will run without alterations, this is true. But it is a risk, unburnt oil may find it's way in the sump over time. And since SVO polymerisates it may cause damage. May! It's a risk, not a fact. Your decision.

However, with the altered timing you can't run pure diesel anymore; or not for prolonged time. Early injection will cause excessive combustion heat and may damage the engine. It is however possible to find a "inbetween" tune that enables you to run both fuels, more or less good.

Mixing of fuels. This is done to thin down the SVO/WVO to make it's viscosity similar to pure diesel. Which is required if it is cold anyway; SVO/WVO looses viscosity much eralyer than pure (summer) diesel. Simple indicator: store a bottle with some SVO/WVO outside and check how liquid it stays.

Not all SVOs or WVOs are the same! Some stay liquid even with negative temperatures...

Two-tank systems enable you to run pure SVO/WVO in winter, but the engine needs to start and SHUT OFF on pure diesel. Which in turn causes some milage on diesel and is considered economical only for long-ish distance drivers. It's basically a choice of how you use your car and how much you want to save/how much you'd liketo invest in runing SVO/WVO. Not more, and not less. Both ways work; either mix fuels or run two tanks. In summer it's not relevant, but if you use the car all year, it gets relevant.

Waste vegetable oil. This is the stuff you can get for free with a bit of luck. But it comes with a price... The injection hardware is manufactured with 1/1000th mm tolerances. ANY dirt in the fuel will wear down the injection pump and nozzles, even if they are made by Bosch. It is therefore required to VERY carefully clean the WVO. By now it showed that simply filtering the oil to 1 micron is NOT sufficient. The current approach is centrifugal cleaning of the oil. This get's out ALMOST any polution. The filters in the car are by far not good enough, neither do they have the capacity required; they'll clog withhin a few miles if you just pour in untraeted WVO

However; one problem remains with WVO; water and acids. They have a similar density to the oil and are mostly emulsified in the oil; resp. can't be separated easily. Cooking is in many cases not a 100% success. And water contents WILL damage the injection hardware! Even if it's make by Bosch. Many WVO users hoard injection pumps

Thanks for reading, this was my view on using vegetable oils with diesel engines. Fueling up with 1l bottles from Lidl or Aldi is - a) time consuming, b) not as cheap as it used to be and c) produces a HUGE amount of plastic waste!! 60l fuel tank leaves you with 60 empty plastic bottles. Count 5 minutes for every bottle (to realy drain it empty)... Have fun with that!

In the end, I decided it's not worth it... I'll continue to run on dinosour juice for now...

Long story short: you CAN just burn SVO. But it's not the best way to do so, even if the whole internet does think so. Few have realy read they'r way into how exactelly diesel injection works...

See I did not disagree with your statement. But it's not just a matter of pouring some SVO in the fuel tank & it's done... To do it properly, there's some tweaks required. Yes, the engine can run it. And yes, it needs a new tune to run properly. And for this some tools are required few people posess, hence they just go on without any tweaks. Which in MY eyes (as I stated) is not the best approach on the veg-oil-burning-thing... But each to theyr own I guess. I'm just pointing out that there's more to it than first meets the eye. And whilst we're at it I felt like pointing out.

And yes I have ried it myself. And I'm sort of involved in the "hardcore SVO fraction" The newest trend is to feed FAT (chicken fat, vegetable fat, cooking fat etc.) to those engines. And it works. But it's even more complicated... And the same statement is true: the engine will run on fat. But it's not a matter of just take a shovel and scoop that solid sh!t in the fuel tank... There's again a bit more to it (a LOT actually).

I never said it won't work. I just said that there's a finer, a less redneck approach to it. No offense! That's all. And this is my final word in this thread.

FACT?
Saloon83 does 100 miles a week in a 60-70mpg car. So he will be paying circa 6 quid per week on Dino and possibly 4 quid a week on veg (70ppl, WVO). He will save apr 12 quid a month.

RISK
If he is unlucky and works 5 days a week, he does a 20 mile round trip. So the chances of running the oil in his system warm is limited, the pump will be working HARD for about the first 2-3 miles each way or 30% of its duty.

WORTH IT ON BALANCE?
Is this duty-cycle going to increase the chances of failure? Can he install a fuel heater and recover that money quickly enough on a high-miler? Fuel pump repairs can be expensive if he is not trained or capable in diesel wrenching - Diesel engineering can be a black art - can he self repair or get mates-rates? If the car fails, does he have another easy mode of transport?

I had to take these into account:
I do 400-500 a week, I run a £800 1986 Mercedes 190D, I use straight WVO at 70ppl and 38-40mpg. I save about £25-30 a week, nearly £100 a month (apr 45l @ 136 vs 70 ppl) and have run it since this January. I have 2 other cars to use if this goes boopsy and has to go offroad for repairs.

Personally, I wouldnt touch WVO or SVO for your particular circs, unless its purely an academic interest.

Hope all this helps, I would be a VERY poor puppy if I had to depend on Dino. Thank God for Mr Diesel and his peanut oil!

Chasesdragons also speaks sense /\

Also, don't use a fuel heater with an SVO / petrol mix

Using 50/50 in summer and 80/20 (Diesel:SVO) in winter in an old Audi 80 TDI, except when it's really cold, and then I don't put any veg oil in. 185k miles on the clock now.

New SVO bought from Costco in 20 litre barrels, and a hand pump bought from ebay with bit of radiator hose on the end, makes the filling operation a lot easier - faster and less spillage. The empty containers are a pain but you can get rid of them in communal bins one or two at a time. I reckon I'm saving £15-ish a tank and MPG is more or less the same. I tried a richer mix in the summer - about 75% SVO - but it was taking a lot of churning to start it - I figured that couldn't be doing the pump any good so didn't do it again.

I haven't advanced the timing but may tweak it into the more advanced end of the spec.

It's a £500 quid car so if the pump goes I'll decide whether to look for another pump or break the car and buy something else. The car had a 'fuel pump fault' when I bought it, so I reckon it'll go at some point.

Your 106 is a mega miler and if it were mine, I'd leave it well alone. For the sake of saving a few quid a month, I'd run it on what's it's been used to for the last 15-20 odd years. Why risk reliability? *

* If the car is a plaything and you don't need it for daily duties, have a play around and see what happens