I think it has to do with Federal Highway Taxes. Off-road equipment users can purchase fuel for off-road use without paying highway taxes. Off-road fuel would also have red dye in it for identification.
I don't have a diesel vehicle, so I'm not up to speed on all of the related issues. But I always thought that low sulfur diesel was a good thing (problems with shortened engine life due to decreased lubricity aside).
So I was filling my car up at one of those combo petrol/diesel pumps the other day and I noticed a sticker that said something to the effect that this is "low sulfur diesel fuel" and its use in "highway vehicles" was prohibited by federal law.
What's up with that?
See this link.
Then why is it for sale at the local (Chevron, I think) station just off the highway? At the same pump as plain old gasoline?
If I remember, I'll try to snap a photo of the warning sign and post it somewhere. It doesn't say anything about it being prohibited due to its tax status. It says its prohibited because its low sulfur.
Low-sulphur diesel is required for 2007 and newer diesel engines, which are designed for the stuff. Older diesels are not but it will still work. It pretty much spells the end of diesels, at least temporarily because the new emission-control stuff that the low-sulphur stuff requires is so expensive now.
Off-road diesel is a completely different issue. Chemically the same as "on-road" diesel, it costs a bit less because it has fewer taxes, taxes being used to build roads, no sense in them paying for the roads they don't damage. And, it's dyed red and the dye sticks to everything, so when the state tax people check for compliance and find a reddish fuel filter in an on-road vehicle, big fines will follow. (yes they do this kind of thing occasionally)
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