I actually concur with mools on it.
I run anything I can get my hands on in the any of the landie diesels upto and including the tdi300
I sat down and punched through some numbers on the cost of various fuel system components VS the cost savings per tank and worked out the mean time between failure rate of various components AND the cost of a worst case scenario failure (mechanicing cost only I didnt factor in the "what if the failure of that component at a certain critical time causes the vehicle to go out of control burst into flames as it careens out of control through an orphanage burning it to the ground prior to coming to a rest in the local cute puppy pound and exploding" type stuff) I also factored in a an additional 2l/100KM to compensate for a degredation in performance caused by accelerated wear on the fuel system.
Ignoring all the cost benefit stuff and going straight to worst case remembering that The td5 runs a 75 PSI fuel rail into injectors that provide the seal between this fuel line and the combustion chamber. Pressure control is achieved at the return end of the fuel rail and the fuel pump can potentially deliver fuel at about 150psi assuming nothing else fails and the pump is delivering to a zero flow condition
The worst case scenario for this is with 2 injectors failing open is the combustion pressure from one cylinder will over pressurize the fuel rail forcing excess fuel into the other cylinder through its open injector. Left long enough this will cause piston failure (if the head doesnt let go first) Ignoring this as the most immediate and likely cause of a runaway engine the piston failure will have combustion gasses blasting into the sump overpressurising the engine, the first place these gasses will exit the engine is through the crankcase ventilation system once that starts happening you will have lubricating oil being fed back into the air intake via the turbocharger air inlet trunk. And theres a runaway.
Whats the cost of replacing a TD5? How quickly can you do it? whats the impact of having your vehicle off of the road for that long?
Given that the cost of TD5 parts is down and diesel is up it might be nearer the balance point if the final 2 parts of the cost/benefit ratio are in your favor (how fast and the impact of not having the vehicle) if you can get enough distance between failures.
Just as an example.... (and remember I dont pay mechanics labour so if you cant do the work yourself you need to factor in those costs)
at current prices in the tdi 300 everytime I refil the tank I save enough money to replace the fuel filter and one injector. If I dont blow any injectors Every 8 tanks I can afford to replace the fuel injector pump with a second hand untested unit and every 14th tank I can replace it with a reco off shelf item.
My current savings on a full tank of fuel is to the tune of $120 for a complete refill. (80ish L ~$1.60/l)
When I did the math for the TD5 the cost for replacing all the injectors, the filter and the fuel pump was a shade over $6k and fuel was around the $1.20/l mark
but as you say, the engine will run bueatifully on whatever you chuck in it for its entire life, but remember that that once bad batch of fuel that sticks a pair of injectors could well mark the end of that life... the same way as a lifetime guarantee on some cheaper tools is only valid till you break the tool then its life is over.
best of luck to you if you decide to run it on vege oil.
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