veg oil in CDI diesels

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growlygrowler

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1990 500SL
Folks

A number of people have warned me off using veg oil in a modern common rail diesel. What I'm interested in finding out is WHY? What problems are associated with using veg oil and/or biodiesel in these engines?

cheers

Dave
 
Veg oil and biodiesel are two completely different things.

Veg oil is just that. Cooking oil from Tesco, and it will destroy any high-pressure common rail system. It's too viscous, and the pumps and injectors won't survive it for long.

Biodiesel starts life as veg oil, but is then chemically converted into a proper motor fuel.
 
Thanks.

I used to have a W124 diesel and ran straight veg oil through it, heating it first using a heat exchanger to lower the viscosity. It worked fine, but I had to replace a lot of rubber seals.

I did also make biodiesel via a transesterification process, but found it messy and expensive - easier just to pour canola oil in the tank...

cheers
Dave
 
Engine oils aren't yet able to cope with biofuels. They thicken, leading to varnishing, gumming and carbonising.
 
Which kinda knocks a hole in the green credentials of using biofuels....

Not really.... changing every 6,000 mls instead of 12,000 mls and running on veg/bio ..... vs changing every 12k and burning DINO diesel for all those 12,000 miles
 
If running WVO for environmental reasons then it's right to take a holistic view. The additional 6k oil change will have an environmental impact, but 5-7L of oil is still quite small when compared to the 600L of diesel burnt over that duration. So through my novice WVO eyes I think 6k oil changes aren't so detrimental to the whole concept.
 
Not really.... changing every 6,000 mls instead of 12,000 mls and running on veg/bio ..... vs changing every 12k and burning DINO diesel for all those 12,000 miles

Totally.

I dunno, I think I've kept quiet on this one for long enough now, but I just don't get the bio/veg oil/alternative fuel haters that threads like this attract. I simply don't get it.

I guess there's a counter argument to any position you care to voice, and these veg/alt fuel threads are there to inform as much as to discuss. Everyone who's used veg in their mercedes has probably done their homework, and if they come-a-cropper, then they're probably mature enough to swallow that pill and move on. That isn't helped by some of the mocking and derision that veg gets.

Seriously, what's the problem? It's not as if we veg burners are skewering babies on spikes.

I can't help feeling that there's a sense of injustice. Injustice that some people are getting their fuel for free (or in the case of svo at c.80ppl), aren't being dictated to by the fuel companies or the tax man, and can claim a smaller carbon footprint to boot.

I've got to say that I'm still on the fence re manmade vs natural climate change, but man, don't hate on the basis that there might be another way.
 
Totally.

I dunno, I think I've kept quiet on this one for long enough now, but I just don't get the bio/veg oil/alternative fuel haters that threads like this attract. I simply don't get it.

I guess there's a counter argument to any position you care to voice, and these veg/alt fuel threads are there to inform as much as to discuss. Everyone who's used veg in their mercedes has probably done their homework, and if they come-a-cropper, then they're probably mature enough to swallow that pill and move on. That isn't helped by some of the mocking and derision that veg gets.

Seriously, what's the problem? It's not as if we veg burners are skewering babies on spikes.

I can't help feeling that there's a sense of injustice. Injustice that some people are getting their fuel for free (or in the case of svo at c.80ppl), aren't being dictated to by the fuel companies or the tax man, and can claim a smaller carbon footprint to boot.

I've got to say that I'm still on the fence re manmade vs natural climate change, but man, don't hate on the basis that there might be another way.

How you come to see hatred in my 2 posts is beyond my comprehension.
Merely, having access to journals specific to the lubricant industry I warn you of the effects of biofuels on the engine oil. I didn't even mention veg oils.
 
How you come to see hatred in my 2 posts is beyond my comprehension.
Merely, having access to journals specific to the lubricant industry I warn you of the effects of biofuels on the engine oil. I didn't even mention veg oils.

The opinion I voiced wasn't directed at you, Bellow. If I gave that impression, that wasn't my intention. You made an elucidating comment about engine oils not being able to handle biofuels, and like I said, these threads are as much to inform as discuss.

I would have to be of the opinion that biofuels have superior green credentials to petrochem fuels.

What I stated stands for the many threads in the past, I'm guessing before you came onboard, where veg and alt fuels have been mocked as 'comedy fuels', and the users, implied as being at best mechanically unsympathetic and at worst, dimly informed. My uncle still thinks I'm playing a mickey-mouse game when I tell him I mix veg-oil in my tank 50/50. I recall a poster stating that the damage to the countryside with the increase in rape-seed production and his consequent hay-fever hell, being what he felt was legitimate grounds for debate. Possibly, but it's hardly the Exxon Valdez.

Here's a :thumb:
 
I agree that biofuels are the future, but that the future isn't here yet!
Firstly the engine oil issue, secondly, it has to be the second generation of biofuels from waste products that do not compete for land with food production.

In the mean time, I would worry that with your mix of fuels, you aren't getting enough detergency from the Diesel to keep the injectors and valves as clean as they need to be. Beyond that, I have absolutely no qualms with what you are doing.
 
Ah, yes, 2nd generation biofuel. I was talking to my friend the other day and we came to the conclusion (this was over the course of the evening in the pub!) that electric cars are a stop-gap till truly renewable energy from waste products/fuel cells hit the streets. Isn't India big on this, methane, at least for domestic applications? (thinking out loud)

I use injector cleaner and only run 50/50 through the summer. I don't put in any oil in winter and haven't had problems so far. The top-end is quieter for sure.
 
I didn't have too many problems with my 300D and found that a few tanks of real diesel, fuiel system cleaner and a good thrash up the road to Aberdeen and back cleared any issues of sluggish starting.

Veg oil does tend to clean the muck out of the system and deposit it into the fuel filter - so I changed the fuel filter regularly. Also (as stated before) I had to replace several aged rubber o-rings on the injector pump output, by the fuel filter etc.

Veg oil has about the same viscosity as mileral diesel when it gets to about 85 degrees, so a good efficient little heat exchanger using engine coolant does the job. I've also experimented with aluminium blocks and heater plugs in the fuel line to raise the temperature, though using coolant worked just as well.

I was going to put a second fuel tank in so I could run mineral diesel to start and then switch to veggie oil, since starting in the cold was a bit difficult. However the price of veg oil went through the roof and I lost interest. Now that diesel is silly prices it may be worth investigating again and resurrecting the 300D to experiment some more
 
we came to the conclusion (this was over the course of the evening in the pub!) that electric cars are a stop-gap till truly renewable energy from waste products/fuel cells hit the streets.

What about a hybrid electric car with small biofuel engine generator?
 

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