Do I need to worry about "bad" or contaminated diesel gas if purchasing a used diesel vehicle?

I’m in the market for a used SUV. Looking at a 2010 VW Touareg with just under 70K miles, but the model I’m considering is diesel. I’ve never owned a diesel car. I know that the diesel fuel is currently priced higher than regular gas but is also more efficient. I know, too, that diesel cars are good for towing and we have that need. My main concern is that when I searched for issues with the 2010 VW Touaregs, I came across some NHTSA reports where the vehicle suddenly stopped driving on highway - seems like the underlying issue in most of these was that fuel pump went bad as a result of bad/contaminated diesel fuel. This seems like an issue with the gas itself not necessarily the vehicle (and I subsequently found this same issue reported with diesel Audis and BMWs). Is bad diesel fuel a common thing that should make me stick with a regular gas vehicle? Or, is it more of an edge case and if we fill the car up at high volume, name-brand fuel stations something that we don’t need to be concerned about?

That would most likely be do to operator error, if gasoline is found in the diesel fuel it was put in the fuel tank by the driver of the vehicle. Gasoline will damage the high pressure fuel pump on a diesel engine.

I have seen this happen a few times with diesel pickup trucks, usually when loaned to someone unfamiliar with diesels, I suspect that this is a more common mistake with cars and SUVs.

Why do you want a diesel again? If you know nothing about them and their maintenance?

Yes you need to be concerned about contaminated fuel. Back in 1981 I had 20,000 miles on my Olds diesel. Coming back from KC, I stopped at fairly high volume truck stop to fill up for the 200 miles left. I made it about 50 miles and I was down to 20 miles an hour for the rest of the trip. Fuel filter was all clogged up. After replacing filters several times, I finally dropped the tank and cleaned it out. The tank was like a swamp with algae growing in it. Sure they have filters now but how often do you clean your tank out? Maybe you can tell after 480,000 miles in a diesel, I’m not a fan and not for the faint of heart or folks trying to save money. Of course in my humble opinion rendered free of charge. Fool me once shame on you, fool me twice shame on me.

find a local VW diesel club in your area, if you can, and ask them. I have found that diesel fuel can vary greatly depending on where you live.

I also know that I wouldn’t purchase a VW. I’ve heard too many horror stories about them and working on them.

1 Like

I remember reading a while ago, fuel pump failures in us were due to sulpher standards. The allowable maximum in Europe is lower than in the US, and that was the cause for diesel fuel pump failures. Just a memory, cannot find internet facts to back it up.

I don’t know about that,after over 40 year’s of driving diesel’s I have had only one fuel pump go out on me.

1 Like

Ultra low sulfur diesel fuel (15 ppm) has been required in the U.S. since 2006, the previous standard was 500 ppm.

1 Like

Fuel pumps or injector pumps? Replaced a number of injector pumps but never a diesel fuel pump. The Stanadyne injector pumps used on the Olds were known to be fussy I guess but I was told the Mercedes pumps tolerated a lot more. No idea who made them but probably Bosch which would be the same as VW. Still I had my fill of head gaskets, $300 starters in 1980’s prices, leaky injectors, injector lines, etc. that I have put out of my mind like a night mare.