Stop Burning Dinosaurs.

June 27, 2009 6:40 AM

Waste Oil Diesel. Any satisfied users?

I found a couple AskMe posts from '05 and '06 and I wanted some more current information.
I've been doing some research into running a diesel Benz on waste cooking oil and I was hoping to probe the hive mind in regards to a couple unresolved questions that I have. I'm trying to figure out if I need a special kit or not. All of the grease conversion kit websites say that a kit is critical. However, I've met people in the real-world who own and operate a number of waste oil diesels without a conversion kit (just an extra superfine filter) who claim to experience no ill-effects. Their cars start and run fine, despite the insistence by conversion kit retailers that the waste oil needs to be at least 160F to ensure correct viscosity. There are also some concerns about the waste oil causing corrosion and damage to the stock fuel system.
The science behind the kit is very convincing. However, pouring grease into a car, starting it, and seeing it run fine is pretty convincing, too.

So, do you run veggie oil in your diesel?
Did you buy a conversion kit?
Did you annihilate your car after running veg oil without a kit?
Have you had years of trouble free driving, just pouring veg oil in your tank?
Do you have an awesome recipe for SVO fuel that ensures stability and correct viscosity?


Thanks folks!

posted by Jon-o to travel & transportation (4 comments total)

I have a good friend who drives a diesel Benz with waste cooking oil, and he's very positive on the experience overall. No conversion kit, just a special superfine filter that can remove particles of one micron. When he runs dry of his own oil, he picks up waste oil at a nearby college for free.

The Benz needs to run on standard diesel fuel oil in the winter, when the viscosity of the veggie oil prevents driving. Apparently, he can switch to veggie oil once the motor is running warm. He's strictly veggie oil in the warmer months, and saves thousands of dollars in fuel costs annually.

The Benz, an entry-level '80s model, is in mint condition inside and out (I've inspected it), and was purchased at a low price. He says that the basic, minimal features and sturdy construction of this model makes it run nearly problem-free, and is particularly suited to veggie oil (for reasons I'm not certain about).

If you sensed a note of envy in my write-up, you're on target.
posted by Gordion Knott at 7:56 AM on June 27

A friend of mine once ran a Vauxhall Frontera (4x4) on pure veg oil, and managed to do something that broke the fuel injectors/turbo. His older vehicle didn't have this part, and has run fine on pure veg oil.

I don't know exactly what part it was that fouled up, but it was something that sprayed the fuel into the engine. I think the extra viscosity of the veg oil bunged the part up.
posted by Solomon at 8:42 AM on June 27

My father in law has converted three separate vehicles to WVO. Two were early 80s Benz sedans (240D in both cases I think). The other was a Ford F250 with a 7-something liter engine, and two tanks. For the Benzes, he added tanks especially for WVO. This allows him to run WVO in the winter; he just starts the car in diesel-mode and switches to veggie-mode after a few miles.

These were all kits, I think. The biggest factor in quality appears to be the restaurant he gets the fuel from. Chinese restaurants generally get good results. Sonic is horrible.
posted by mkb at 1:01 PM on June 27

I have a 2001 VW Jetta that I've been running on used cooking oil for the last four years. I have an Elsbett single-tank kit installed, which is somewhere in-between a two-tank kit and an unmodified engine.

For me running veg oil has been a very interesting exercise. I got into it as an experiment, driven by environmental motives -- basically, to answer the same question I think you're asking. And for the first three years, things went just fine. I ran on probably 85% WVO / 15% biodiesel all year long with no problems (save for the ONE TIME the restaurant I got my oil from ran out of veggie oil and I put the new ultra-low sulfur diesel in the car. The injection pump gaskets let go, something that happened to a lot of TDIs when ULSD was introduced, regardless of whether they had been running petrodiesel, biodiesel, or veg oil. Grrr.) However, over the past year the car's power has suffered a steady decline. I won't bore you with the details (unless you want -- email's in profile), but basically what happened was that veggie oil's higher flashpoint and its greater propensity for polymerization meant that unburned fuel was condensing back in the turbo, gradually turning it into a $1100 piece of metal glued together with soot. I'm actually picking it up from the mechanic today, after a thorough cleaning that was Not Cheap.

Unfortunately, this is a pattern seen a lot with veggie cars. People do the conversion, get great results for the first 40,000 - 60,000 miles, then start to have major problems. These problems seem to be in three places: the injection pump, the intake, or the engine itself. The rings seem to be the weak point for old Mercedeses -- coke deposits on the rings cause blowby, which can result in engine oil dilution and eventually polymerization of veg oil in the crankcase. Of course there are lots of stories about people running 250,000 miles without a problem, but those folks usually do all a lot of highway miles. If the engine is good and warmed up when you're introducing veggie oil, then all of the VO burns completely and doesn't go places it shouldn't. But if most of your driving is relatively short trips, you're almost guaranteed to have problems eventually regardless of what kind of kit you have.

So, that's the bad news. The good news is that if you are contemplating running veggie oil in a mid-80s non-turbocharged Benz (like the 240D), then you're probably picking the platform that is most likely to give you a good result. Those motors are built to last, and it takes a lot to kill them. Your profile says you're in South Carolina -- it's warm enough there that you might be able to get away with running VO in an unmodified Benz for quite a while.

Regardless of whether or not you decide to go with a kit, mkb is correct: fuel quality is very, very important. Be prepared to spend some money and time fabricating a fuel treatment system. Corrosion issues are linked to water in the fuel, so you need to dewater it either by settling or heating. Filtration is also very important. I think the MBZ fuel filter is a 10 micron filter -- you will need to filter down to 1 micron (nominal), and still be prepared to change filters much more often than you would running petrodiesel. You should also add a standard fuel additive (Stanadyne, Power Service) at an increased dosing rate. For lots of ideas on fuel treatment systems as well as other SVO talk, try the SVO section of the biodiesel Infopop forum. There is some great information there but be prepared to wade through some serious crap and ridiculously outsized egos to get to it.

I still haven't decided what I'm going to do with my car in the future. I got a lot out of the experiment -- about 45,000 miles of carbon-neutral driving, as well as a new appreciation of the volume of fuel I consume every year (it's a lot easier to see when you're the one collecting and handling the fuel rather than just pumping it straight from one unseen tank to another). However, between the cost of the kit and my recent repair, despite getting my fuel for basically free I just about broke even over the entire four years. I'd like to continue running veggie oil but I don't want to assume the downside economic risk again. (And the environmental risk -- those parts don't grow on trees.) I may run commercial biodiesel for a couple of years until I can get a reliable electric car, which would be a better fit for the short in-town trips I mostly do these days.
posted by harkin banks at 2:07 PM on June 27 [1 favorite]