Graysilm.......one of the inherent qualities of BioDiesel is that it is a great injector and fuel system purge. It is a great carbon solvent! Even if you only occassionally fill your tank with 20 gallons of B20 for an extra $.30 per gallon your essentually getting 4 gallons of solvent/purge/Biodiesel flowing through your fuel system for an extra $6.00. A liter of "Diesel Kleen" or "Purge" would cost you more than twice that and probably would not do as thorough a job.........
I have run everything from B20, B99 and mixed my own ratio of B50 with no ill effects in my 98 with the exception of a slight loss of mpg with the B99.
The car has over 170K and the engine is running better than ever since I started using Biodiesel on occassion.

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FRED

Daily Driver: 98 E300TD 199K
Hobby Car: 69 Austin Mini
Past Diesels: 84 300SD, 312K
87 300SDL, 251K
94 Chev. K-1500 6.5Ltr.TD, 373K