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Changing from veg oil to diesel


Lewis
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My vehicle was previously running on a 50/50 veg oil/diesel mix, and now i want to only run on pump fuel. I'm planning to run the tank as low as i can before I brim it with diesel, then dump a bottle of injector cleaner in and run the tank empty again, then fill up and change the fuel filter.

Have I got this in the correct order (injector cleaner then filter)? And have I missed anything I should be doing?

Many thanks :)

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None of that should be required, just switch back. Diesel is dirtier than veg and the issue with switching the other way is clogged filters from the increase in solvent-ability and crud coming loose. Going back to dino-diesel does not have the same issues. Probably a good idea to change the filter and clean the sedimentor bowl after you've run for a bit.

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Oh, okay, well i've already got the stuff so I'll do it anyway.

The veg oil was pre-loved from the chippy and the filter was changed regularly because of this, so I just kinda thought my above plan would be a good way to see off any dregs of veg oil.

Plus, injector cleaner always helps in a 21yr old engine :)

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If you have just been running a mix with no heater on the fuel line then definitely change the engine oil and filter as well ASAP. Finally got mine up and running on a twin tank set up with heat exchanger and am very happy with it so far. No noticeable difference in running on either tank. Can't be bothered with the collection and processing of old oil though so have just bought an IBC full of pure British Rapeseed oil for 75p a litre. Thats a saving of over £800 on the Disco doing 10K miles a year @ 25 mpg average.

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i've run my 300tdi 90 successfuly on a 50-50 mix with no preheat for some time (except winter) with no problems of polymerisation, smelly engine oil, engine oil volume increasing, fuel filter blockages, etcetcetc.

Only thing i have noticed in all that time is that when the temperature drops close to freezing over night (0-5C) then it can feel a little lumpy when feathering the throttle at say 30mph in 4th on flat roads. Once the engines warmed up its fine.

but i have just bought a heater element that fixes to the high pressure pipes from the inj pump to the injectors and supposedly heats the high pressure pipes up to 120C making 100% veg oil the same viscosity and atomisation properties as diesel. Takes less than 2 mins to heat the pipes and because of the very low flow rate through the pipes you dont lose the heat and keeps it constantly hot.

Not sure how those little inline fuel heaters work really, as once you;ve warmed the fuel to 70C, it then passes through the fuel filter and cools down a bit, passes through the inj pump and cools down a lot (big lump of metal!) and slowly....oh so slowly.... passes up the high pressure lines into the injectors. By the time its got there it'll be cold!

edited to add - i use soya veg oil, it has a lower flash point to sunflower and rape oil and a slightly higher cetane rating. Oh, and it costs about 72p/l when buying 20l barrels from the local indian cash and carry.

;)

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Nick, I've always been led to believe that when the oil passes through the injector pump it's heated, not cooled. The pump is bolted to the block, so as the block warms up the heat transfers to the pump. The main advantage of the pre-heater is that the fuel is heated before the filter, and is less likely to clog up the pipes.

I have seen first-hand that when you put too much solvent (in this case mis-fuel, 70/30 petrol/diesel) into the oil then the heat of the pump causes vapor-lock. Interesting when towing on a motorway hill... :blink: The driver was less than amused.

It's the pump that seems to be a problem, at least in a transit, as the diesel provides the pump's lubrication, whereas veg oil doesn't... I've also been told to watch for the rings getting gummed up, and letting oil past, although I don't really know how you would go about watching the rings. :huh:

HTH

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The purpose of heating the oil before the filter is to firstly aid flow through the filter, and secondly to melt any high melting point fats that would clog the filter when cold.

The third purpose is really only valid when using lucas injection pumps. These don't take kindly to thick fuels and will seize due to lack of lubrication. When heated, the oil is thin enough to lubricate sufficiently. With these however, you need to use the hot fuel (diesel) to heat the pump before switching to veg (twin tank system). Bosch pumps don't suffer from this so much - however wear of the cam plates is accelerated slightly with thicker fuels.

Heating the injector lines is pointless IMHO. Once the veg is at the injector, it will be injected at the temperature of the nozzle tip - *ing hot! If you are heating the lines when the engine is cold, then the opposite will apply - your veg will be stone cold when injected...or at least at the temperature of the head. This is why there are some cold starting issues with DI engines and veg.

These electrical fuel heaters are also next to useless. Smartveg did a study on them as part of their product development. They showed that 200W of glowplug heating fuel was not sufficient to raise the temperature of the fuel enough for lucas injection pumps. Coolant heat exchangers seem the only way to go.

And yes - due to the action of the injection pump, the fuel normally comes out hotter than it went in.

You can keep an eye on ring condition by monitoring blow-by. Bizzarly water injection has been shown to cure stuck rings!

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