Make:

I know three people who've done "greasel" conversions, and all three yanked the systems out within a year, going straight biodiesel (which is much less expensive than this marketing blurb makes it out to be). Don't know where they get 0.15c/gal, either.

To use a dual fuel system, you need to figure out how much distance you can run on what's in your fuel lines so that you can switch back to diesel early enough to flush the grease out of the fuel rails. And you need to do this every time you stop the car for more than ten minutes. If you forget, it can be a very annoying and time consuming experience to manually heat your fuel rails to get the congealed grease to flow again. Ever have your car serviced? You will need to carefully explain that they should never switch the car to oil unless they have a similar car of their own and know exactly what they're doing. This is how automotive horror stories happen.

Second, the variability of what you'll find in a "grease bin out back" is truly astonishing. Water, food particles, rust, solid fat, cigarette butts, dead animals (both preserved and severely decomposed), paper, random garbage: all of these things do bad things to fuel pumps and fuel injectors. When you take the time to make biodiesel from oil, you get to make certain that none of these get into your tank. Yeah, it costs a little (about a dollar per gallon for the chemicals), but the really annoying part is handling the grease at the restaurant. The rest of it is fairly benign by comparison.

Third, unless you have an old engine and don't really care about how long it lasts, you're going to have serious carbon build-up (coking) in your injectors, cylinders, and engine oil. Glycerin (the chemical in oil that's swapped out when you make biodiesel) doesn't burn well except at very high temperatures. Temperatures that are not always found even in a warmed-up diesel engine. When glycerin doesn't burn well, it leaves very sticky and nasty carbon deposits that build up over time. Diesels are renowned for lasting a very long time. Don't throw that advantage ($$$) away just to save a few dollars on gas.

Finally, most restaurants around the country already know that their grease is worth something and already have an agreement with a grease recycler (most fast-food fryer grease has been recycled at least once). If you touch that stuff after being told or seeing a label on the tank indicating ownership, you're committing larceny, so make certain you have permission before "just taking some grease". With the increased popularity of biodiesel, many of the best restaurants (Oriental food restaurants tend to have the best oil by a long shot, in the mall is even better) have already been hit up by someone else. You'll have to do some serious looking, or hook up with a local biodiesel co-op to get a reliable supply of oil.*

* Unless you live in California, that is. There are so few diesel cars there (due to one rather idiotic emissions law), that biodiesel really hasn't had a chance to build up and there are still plenty of restaurants around...

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Well that's some scary stuff, there rabagley!
I live in Southern California, and need to replace my dying Saab. I have about $4500 at my disposal, and have been looking into CNG -for which it appears I would need to travel to Phoenix to pick up, and as of today, the grease-mobile option. Unfortunately, I cannot find enough info (yes, even on the wonderful www) to really take any sort of plunge.
Does anyone kow of anyone in LA area who runs a CNG or veggie car?

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