Mercedes 300d 1984
Biodiesel may have superior lubricity, but also blocks the nozzles.Nonsense. Many people run 100% biodiesel without problems in the 617 engine. I have read dozens of first-hand accounts, but not one suggesting that biodiesel blocks the nozzles.
Biodiesel usually has a higher get temperature, meaning it gels long before diesel, so avoid using this in winter.Most people just reduce the percentage of bio in the winter. It depends on your climate. You can also add an anti-gelling agent just like you might for regular diesel.
No engine has been developed for use with biodiesel at the time, so there's no telling about the long term effects it could have.There are certainly lots of anecdotal reports out there suggesting that long-term use of biodiesel causes no significant problems for old Mercedes engines. Perhaps you are thinking of straight vegetable oil (SVO)?
Mercedes allows no more than 5% biodiesel.This is true of late-model Mercedes engines that use post-injection and diesel particulate filters, but as far as I know there is no limitation or even recommendation published by Mercedes regarding biodiesel use in our cars.
Biodiesel also has a lower energy density than diesel, so expect worse fuel consumption.Theoretically true, but in practice it's hard to see any significant fuel economy difference using 100% biodiesel versus 100% petroleum diesel. Driving habits and conditions make a much larger difference.
Let's talk about the reasons why biodiesel makes sense:
1) Just a small percentage mixed in with your petro diesel adds back lubricity in the fuel that was removed in the switch to ultra-low sulphur fuel.
2) Emissions improve dramatically. There is a lot of documentation for this from respected sources that have actually done tests. As little as 20% bio can improve certain emissions. And the car exhaust smells better!
3) Biodiesel is carbon-neutral.
4) Biodiesel is a domestic product, not imported from overseas. As they say, "No war required."
5) Biodiesel helps clean out your fuel system. You will likely have to replace a fuel filter or two in the process.
6) Biodiesel is biodegradable. If you have to change a fuel filter and dump petroleum on the ground, that's not too friendly to the environment. It's essentially toxic waste. But a few ounces of biodiesel will quickly biodegrade once exposed to oxygen and heat. After all, it's basically just vegetable oil that has had the glycerin removed.