Running the Diesel in Mexico

When the United States made the switch to ultra low sulfur diesel (ULSD) with model year 2007, it may have caught some in the RVing community off-guard. For those of us with "older" (should we say, "venerable") diesel rigs, the "new" fuel can cause grief with fuel system leakage, and a noticeable loss of fuel economy.

But what about those with the "newer" engines that US law mandates be operated only on the ULSD? Filling up the tank here in the US is not a problem--stations across the country have made the switch to the super low sulfur diesel. But for those taking the rig into Mexico, there could be some problems.

While the Mexican government has directed that diesel produced there should meet the US standards of ULSD by now (September 2008), the reality is things aren't moving quite at that speed. Some insiders think that it could be as late as 2010 before Mexico meets the ULSD standards, because at this time, the refineries are still catching up with changes to gasoline. Still, in border towns along the frontier, it is said that most (if not all) of what is sold as diesel is ULSD, in order for Mexican trucks to be able to cross into the US legally.

But getting away from the border, the standards are not tight, and like as not, most feel you'll be buying "low sulfur" diesel--the kind we used to sell in the states. What happens if you run your ULSD designated truck or car on the "low sulfur" variety. Dire warnings have been posted by the government. One energy site in Alaska suggests engine damage could result.

But the web site, greendieseltechnology.com has this to say: "Tests indicate that filling the tank of a low-emitting diesel vehicle with regular diesel fuel on a rare occasion won't damage the filter system. However, this shouldn't be a habit. Use on a repeated or regular basis would do damage."

That leaves RVers with the newer diesel engines in a distinct quandry. When in Mexico there's really no way to know if the diesel you're pumping is really ultra-low or just "low." And you can't be reasonably assured that if you do pump the "wrong" stuff if you'll suffer damage or not. It's a troubling issue, and one that looks like it'll be with us for some time.