WATER IN DIESEL FUEL

I have a 2015 3500 dually diesel. I’ve seen a few people discuss water in fuel on a popular RV site I visit. These owners said they were getting water in the diesel fuel from a conventional service station, but the WIF sensor didn’t alert them to a water problem. They went on to say that repairs can be expensive.

My questions:

• I use the Wal-mart diesel fuel additive with each fill-up. Does this really help with this potential issue?

• I change the fuel filter every other oil change. Is this smart to do?

• Is there a better fuel filter I should use?

• Is there anything else I can do to protect against damage from a bad service station with water in its fuel tank?

Winston Falco Waco, TX

Hi, Winston,

First off, water is often exaggerated as a problem for diesel owners. Water in fuel does happen occasionally but not as often as many diesel pickup owners might think. For example, I've been driving a diesel pickup since 1986. I've never identified any water in the fuel or found any water in a fuel filter; nor have I seen a water-in-fuel warning (WIF) lamp. I've driven all over the West and as far east as Ohio from my home in Montana.

Those trucks that are more at risk are usually located in moist/humid areas of the country or areas with significant precipitation. For example, spring floods, hurricanes or similar weather events can contaminate the underground fuel storage tanks used by fuel stations. Don't buy fuel from a station that had been flooded. In addition, I also don't buy fuel from a brand-new fuel station. New tanks could be contaminated with water and all sorts of junk. I found this out the hard way:

I plugged two fuel filters with manufacturing debris before I got it all. So, buy your fuel from a known good station, preferably one that does a lot of business, because higher turnover improves your odds.

If a diesel pickup owner can prove there was water contamination that damaged the fuel injection system and that the WIF (water-infuel) sensor didn't produce a driver warning, you should have recourse with the truck manufacturer's warranty coverage. On the other hand, if you're using the wrong type of fuel treatment, you could be on the hook.

For example, GM specified in bulletin #0306-04-017, dated March 13, 2003, that Stanadyne and Racor diesel fuel additives had been approved (but not necessarily recommended) for use in their diesel engines. This is partly because the Stanadyne and Racor diesel fuel additives are a water demulsifying variety (they tend to separate water from the fuel), meaning that they work to allow free water molecules to coalesce. These can then be drained away using your fuel filter's water drain valve once you've been alerted to a water-in-fuel problem. Some of the other brands of fuel additives emulsify the water, allowing water to blend with the fuel and pass through the fuel filters and fuel injection system. There is quite a lot of debate about which is better, but ... GM provides the warranty.

Those fuel additives that emulsify water (cause water to mix with the fuel) might include chemicals such as alcohol or acetone, which act as water absorbers. The mainstream fuel treatment manufacturers do not use alcohol, which is largely condemned by all diesel fuel injection system manufacturers. You shouldn't use a treatment that contains alcohol either. Any fuel treatment you use should be labeled as being safe for the current diesel fuel emissions-equipped diesel engines. What this “safe” declaration really means is that it won't harm the oxidation converter and diesel particulate filter in the exhaust system and won't increase the bad components in the exhaust gases. A certified diesel fuel treatment also shouldn't jeopardize your engine/fuel system warranty.

As long as you change the fuel filter according to the schedule called for in your owner's manual, you're satisfying the requirements for warranty coverage (regarding the fuel filter service). Changing it sooner won't hurt. Be sure to document the fuel filter service if you do it yourself (filter brand/number). Keep receipts, date and mileage.

Due to “surface tension” and other designed-in features of fuel filter media, a quality diesel fuel filter element will resist water from passing through its media; and water is heavier than diesel fuel, so it tends to accumulate on the bottom of the fuel filter housing or canister. This is where the water-in-fuel sensor is located. It should alert the driver when more than a couple of ounces of water accumulate on the bottom of the fuel filter housing. Diesel fuel is a poor conductor of electricity, while water is a good conductor. The vehicle computer simply measures the current flow (voltage drop) between the two probes used by the WIF sensor to determine the conductivity of the liquid in the fuel filter assembly.

If you have some experience with, or have a history of, buying diesel fuel with fuel quality problems, additional fuel filtration would be recommended. Otherwise, your factory fuel filter should provide all the protection you need—at least through the warranty period. If you tend to own the same truck past the warranty period, additional fuel filtration could save you money in the long run. Always buy the latest recommended factory fuel filter, not a cheap knockoff. I'm told the factory Duramax (Bosch-recommended) fuel filter has evolved through four generations in the past 12 years. This tells me Gm/bosch is/are adapting to the real world, in terms of fuel quality and the need to minimize warranty exposure by providing a better fuel filter. Good luck.