What would happen - Diesel & Gas mix-up?

[mjammer]

A local store somehow got Diesel in the gas tanks and gas in the diesel tanks. Here is a link to the article from the local paper:

http://www.fortwayne.com/mld/journalgazette/news/15340060.htm

My son and I were talking about this and was trying to figure out just how catastrophic this would be to the diesel. Anybody ever done this on accident?

[Stlheadake]

There have been a couple of (panicked)member posts about this. It seems that it isn't as bad as one might think. According to the posts, the truck will run for a very short time, then shut down. In the two most recent posts that I can recall the pro's advised to drain the tank, change the filters, and drive it like you stole it! Apparently basic daily driving isn't so bad, but if you were working it pretty hard when it stops, it could be worse.

I have no first hand experience here, just what I read. I would have thought that the damage would be fairly catastrophic myself. As for diesel in the gasoline, it would just foul out and kill the gasoline motor. Diesel is too heavy and doesn't burn well in the gasoline engine.

My buddy has an auto repair shop where he routinely gets diesels with contaminated fuel. We have burned 20% diesel in our garden tractors, log splitters, and other gasser engines to get rid of bad fuel. It smells a little different, but it burns.

[mjammer]

That's interesting as I thought is would be catastrophic too. I wouldn't think gasoline at the high compression of a diesel would be good, i.e. a big boom.

[DmaxMaverick]

That's interesting as I thought is would be catastrophic too. I wouldn't think gasoline at the high compression of a diesel would be good, i.e. a big boom.

Another part of the equation....Volume.

Regardless of what gets injected into the cylinder, it's still only as much as what would have been #2. Gas has a lower BTU than heavy oils, so even if it did all "blow up" in there, it would still be a very small explosion. Gas doesn't combust nearly as violently as #2 (hence the heavy Diesel hardware). The other "volume" is air. Once gas gets away from the ideal ratio of 15:1 air/fuel, it doesn't burn well, if at all, under compression, and since the Diesel intake isn't restricted (theoretically), the air/fuel is always way off.

The biggest issue with gas mixed in your #2 is the lack of lubricity. Gasoline can dilute the lubrication properties of the fuel. If there is a high enough concentration, it can "wash" the lube off of internal moving parts, like in the IP.

[mjammer]

Thanks DM, Dang, I learned something today. I guess my day is done ;)

[JohnC]

I wouldn't think gasoline at the high compression of a diesel would be good, i.e. a big boom.

Don't forget, the reason this is an issue in a gas engine is because the fuel is already mixed with the air before the compression starts. In a Diesel, the fuel isn't introduced until the right moment, so preignition is not an issue.

On a different note, there was an incident a few years back where some 10 - 15% diesel fuel was accidentally mixed with aviation gas. The results were disasterous. The excess BTU's and reduced detonation margin in an air cooled engine was a formula for melted pistons.