Ultra Low Sulfur Diesel (ULSD) Fuel in Mexico

There are many questions and lots of confusion about the diesel fuel situation in Mexico when it comes to the newer US diesel engines which require ultra low sulfur diesel (ULSD) fuel. This is a summary of my findings as best as I can determine after researching the issue. I am still learning and would appreciate any additions or corrections to this information.

First, Some Background Information on ULSD

Why do we even have ultra low sulfur diesel (ULSD)?

Since 2007 the US EPA has mandated the use of ULSD in all on-road diesel engines to reduce emissions. All on-road diesel sold in the US is now the ULSD. There are 3 different types of diesel fuel, containing 3 levels of sulfur: You can see they have really reduced the sulfur level with the ULSD.

  • "Regular" Diesel
    • 5000 ppm sulfur
  • Low Sulfur Diesel (LSD)
    • 500 ppm sulfur
  • Ultra Low Sulfur Diesel (ULSD)
    • 15 ppm or less sulfur

The sulfur in the diesel fuel contributes to the lubricity of the engine, so the ULSD has required engine redesign. Additionally, the exhaust system has been redesigned to lower the emissions to the lowest level possible.

Four major components to the exhaust system designed to reduce emissions:

What is the effect of burning LSD in the newer engines?

What about the diesel fuel in Baja California, Mexico?

Mexico has a mandate to have ULSD throughout the entire country by 2009. Obviously, they have not met this deadline. The fuel system in Mexico is nationalized and called Pemex.

The diesel fuel signs at the Pemex stations will be black and can be labelled as follows:

  • Diesel
    • 5000 ppm sulfur
    • sold for off-road and marine use in Baja
  • LSD Diesel
    • low sulfur diesel
    • "diesel sin" or "bajo azufre"
    • 500 ppm sulfur
    • sold in southern Baja

  • ULSD Diesel
    • ultra low sulfur diesel
    • "UBA" or "bajo azufre ultra"
    • 15 ppm (or less) sulfur
    • probably sold in northern Baja
    • lower cetane number than higher sulfur content diesel
    • has to be refined from higher grade crude oil

However, I have never personally seen one of the UBA signs. Anybody else out there seen one?


Here is the disclaimer: I am not an expert, so you will have to form your own conclusions and act accordingly. I encourage you to do your own research. However, this is what I believe to probably be true.

  1. Pemex says that ULSD is available in Mexico along the border, Mexico City, Guadalajara, and Monterrey.
  2. I believe ULSD is also available throughout the northern half of Baja California Norte as far south as El Rosario.
  3. The diesel fuel in Baja California Sur is shipped by barge from the mainland to La Paz, and then distributed from there by truck throughout the entire state as well as the southern part of Baja California Norte. This is the 500ppm LSD, not ULSD.
  4. A trip to Mexico with your newer diesel pickup probably should cause no permanent damage to the DOC or DPT.
  5. The SCR (new since 2011) and its monitoring computer may be more problematic but is also probably manageable, as discussed in the lengthly article below by Ted White.
  6. I wouldn't go to Mexico in my newer diesel pickup without:
    • Ted White's e-mail address: whitetmp@aol.com
    • 5 gallons of DEF
    • a new oil filter
    • low-ash oil
    • a fuel filter
    • not related to the fuel system, but I would also take:
      • portable air compresser
      • tire plug kit


From 3/13/2013 Baja Pony Express, by Ted White

The Owners’ Manuals of Dodge, Ford, and GM diesel powered pickup trucks have been warning, ever since the latter half of 2007, that using Mexican diesel fuel, which is higher in sulfur content than the fuel in Canada and the USA, could cause serious damage to the emissions system, and that any such damage will not be covered by warranty. Despite these warnings, hundreds, if not thousands, of Snowbirds have driven their 2007.5 and later model diesel pickups into Mexico over the past 5 years.

So what has been the typical experience for owners of pickups using Mexican diesel fuel, and what exactly are the potential risks? This article sets out to clarify the issue, first by explaining how the emissions system works in 2007.5 and later diesel powered pickups, and secondly by identifying known “real world” issues and risks reported to the author by owners of 2007.5 and later model pickups. This article is not to be interpreted as an endorsement of the actions of owners who have ignored their Owners’ Manuals warnings. It is purely a sharing of information, in the interests of ensuring that affected owners are fully informed about their options and risks. Any decision to drive a 2007.5 or later diesel powered pickup truck into Mexico, and run it on Mexican fuel, is the sole responsibility of the owner.

If you don’t want to wade through a lengthy description of the emissions system operation, but would like to read about symptoms which might occur when using Mexican diesel fuel, and which late model pickup trucks cope well with the sulfur levels in Mexican diesel fuel, skip to the section labeled “The Question Everyone Asks”. If you have personal experiences to share, good or bad, please provide your input and feedback, by emailing me at whitetmp@aol.com. I have been gathering as much data as possible, since late 2007, so that there is a knowledge base to draw upon when, or if, an owner contacts me with a fuel related problem. The database already in place has helped clear emissions system fault codes for a number of owners, and is getting more and more useful by the day.


Beginning in the second half of 2007, diesel powered pickups started being fitted with a new type of emissions system designed to reduce the amount of oxides of nitrogen (NOx) leaving the tailpipe, and virtually eliminate emissions of black soot (carbon) in the exhaust.

Reductions in NOx at that time were achieved mainly by sending some exhaust gas back into the engine intake, (Exhaust Gas Recirculation, or EGR), a process which reduces the amount of oxygen available for combustion. This in turn causes oxygen to be stripped out of the recirculated NOx, so that less NOx, and more Nitrogen exits the exhaust pipe. Nitrogen is a harmless gas which makes up approximately 78% of the air we breathe, so converting NOx to plain old Nitrogen is very desirable.

The second, and biggest change, introduced in the latter half of 2007, was the incorporation into the exhaust pipe of a diesel particulate filter (DPF) to trap soot from combustion. We’ve all been behind black-smoke-belching diesel powered vehicles from time to time, so most of us are happy that post 2007 diesels emit no sooty exhaust. The carbon is captured, instead, by a special ceramic “honeycomb” in the DPF. The DPF though, gradually fills up with soot, so, typically around once for every tankful of fuel, the soot has to be burned out of the DPF. This is achieved by injecting fuel into the exhaust stream, either by the engine fuel injectors during the exhaust stroke, or by a separate fuel injector in the exhaust manifold. The injected fuel burns, using oxygen released by a special catalyst in the exhaust line, known as the Diesel Exhaust Catalyst (DOC). This raises exhaust gas temperatures high enough for the soot in the DPF to “light off”, and combine with oxygen to form carbon dioxide (CO2), another gas found in our atmosphere, and one we all exhale with every breath. This process is called “regeneration”.

In order for all of the above emissions equipment to work properly and efficiently, a change also had to be made to the diesel fuel available at the pump. This is because the sulfur content of standard diesel fuel in North America prior to 2007 was high enough to “poison” the DPF, by depositing in the DPF sulfur compounds formed during combustion. These compounds tend to clog the ceramic pores, gradually building up over time, until the efficiency of the DPF is reduced, causing more and more frequent regenerations. Eventually, the DPF becomes so “poisoned” that it no longer functions properly. The good news, however, is that extensive testing by the EPA and manufacturers, prior to the first DPFs being installed in vehicles, showed that permanent damage only occurred if higher sulfur fuel was used continuously for more than 40,000 miles. In other words, the DPF normally recovers completely after occasional use of higher sulfur fuels. This is why Snowbirds, who have been bringing their 2007.5 through 2010 model pickups into Mexico, have not reported in the on-line diesel forums any negative experiences. As soon as the truck returns to burning ultra low sulfur diesel fuel in the United States and Canada, after a winter in Mexico, the sulfur compounds burn out of the DPF during soot burning regeneration cycles.

For most owners of 2007.5 through 2010 diesel pickups, there are usually no observable effects from burning Mexican diesel fuel, but sometimes regeneration cycles cause blue colored smoke in the exhaust for a few minutes as the sulfur compounds burn off with the soot. The blue smoke can be quite noticeable if regeneration is happening at slow speeds, such as in-town driving, and can easily be mistaken for an oil burning problem, such as worn rings, or failed turbocharger bearings. Embarrasing though it might be to have clouds of blue smoke billowing out of the exhaust pipe of a recent model pickup, if the “problem” quickly disappears, it was probably just an indicator of a soot burning regeneration under way.


For owners of 2011 through 2013 model year pickups, things are quite a bit different. Starting with the 2011 model year, Ford and GM introduced further changes to the emissions control system, using urea injected into the exhaust to drastically reduce NOx leaving the tailpipe. This new system allowed for a reduction in exhaust gas recirculation, leading in turn to quite a big jump in power and torque for both Ford and GM engines, up to around 400 HP and 800 ft lbs of torque. Dodge chose instead to maintain higher levels of exhaust has recirculation to meet the new emissions requirements, a decision which caused them to drop behind Ford and GM in terms of power and torque, but gave them a selling "advantage" to say that their vehicles did not need to use Diesel Exhaust Fluid (62.5% distilled water and 37.5% urea). As of the 2014 year though, Dodge pickups will use urea injection, because exhaust gas recirculation alone can not achieve the latest NOx emission reduction requirements.

The illustration below is typical of a 2011 or later diesel pickup emissions system. It shows all of the components of both the 2007.5 to 2010 models, and the 2011 through present day models. It will apply fully to Dodge as of the 2014 model year.

Here's a basic explanation of how the entire system works:

  1. At all times, a varying amount of exhaust gas, controlled by a valve, is recirculated through an exhaust gas cooler and back into the engine intake. This assists in the reduction of oxides of nitrogen (NOx) by limiting the amount of oxygen available for combustion. Some of the oxygen for combustion has to be "pulled" away from the nitrogen atoms in the NOx.
  2. The DOC, or Diesel Oxygen Catalyst, uses oxygen in the exhaust to convert carbon monoxide (CO) to Carbon Dioxide (CO2) plus hydrocarbons (HC) to water (H2O) and carbon dioxide. The DOC is typically at least 90% efficient.
  3. The DEF tank, which all 2011 and later Ford and GM pickups utilise, contains Diesel Exhaust Fluid (DEF). The urea (CO(NH2)2) in the fluid is injected into the hot exhaust just ahead of the SCR. As the urea enters the exhaust stream it turns into ammonia (NH3). This ammonia reacts with NOx in the SCR to form water vapour, CO2, and nitrogen. Reduction in NOx is typically in the range of 90% or more.
  4. Finally comes the DPF, which captures the soot in the exhaust. Pressure sensing across the DPF is the main signal for a regeneration (soot burnoff) to begin, at which point the fuel injector in the exhaust manifold, or the engine injectors during exhaust strokes, begin injecting fuel into the exhaust. This fuel burns fiercely, raising exhaust gas temperatures high enough to oxidise the carbon in the DPF, and convert it to carbon dioxide. Regeneration can last as long as 30 minutes, depending on the individual manufacturer programming.
  5. The end result of all of this exhaust treatment is extremely clean exhaust. Emissions are almost entirely composed of water vapour (H2O), carbon dioxide (CO2), and nitrogen (N), which are all naturally occurring components of the air we breathe.


So, the question everyone asks is, “Which late model diesel pickup best tolerates the higher sulfur Mexican diesel fuel?”

In general terms, Dodge Ram has the edge through the 2013 model year because there is no SCR, which is the most sulfur sensitive part of the system. This means, if the only thing you care about is minimal sensitivity to sulfur in the fuel, a Dodge Ram appears to be the best choice. As of the 2014 model year though, Dodge will be using DEF and an SCR, so the sulfur tolerance advantage will disappear.

For Ford and GM products, 2007.5 through 2010, the issues are minimal, typically only an occasional “blue smoke” regeneration, and most owners are unaware of any sulfur effects. If you prefer a Ford or GM truck, these model years do not seem to require any owner intervention to clear codes, and for all intents and purposes operate exactly as they would back in the USA or Canada, as long as they do not remain on Mexican fuel for more than 40,000 continuous miles.

Unfortunately, the SCR, found in 2011 and later model year Ford and GM pickups, is quite sensitive to sulfur in the fuel, and is easily poisoned, resulting in less than ideal NOx reduction. Eventually, for many owners, the decline in SCR efficiency results in a “Check Engine” light, or “Poor Quality DEF” light coming on. The problem, of course, is not due to bad DEF, but the vehicle computer interprets the out-of-spec NOx levels as being caused by the DEF not doing its job, so that’s the message it gives to the driver. For 2010 through 2012 Ford and GM vehicles, a normal regeneration cycle, or raising exhaust gas temperatures by towing a heavy trailer for 30 minutes, or travelling at, say, 75 mph, for about fifteen minutes, will usually clean the SCR enough to return tailpipe NOx levels to normal. Following one of these activities, the NOx sensors will indicate to the onboard computer (ECM) that things have returned to normal. This does not mean that the warning lights will extinguish immediately though. Typically, it can take 20 miles (35 kms) or more, and 2 or 3 separate engine starts, before the warning lights go out. Many owners, it should be noted, based on reports I have collected since 2010, have never experienced this type of scenario, and have never seen any warning lights, while others have seen them every few weeks while in Mexico.

The 2013 model year appears to have brought with it a further complication, because the Environmental Protection Agency apparently made changes to the requirements for NOx monitoring for 2013 and beyond. Monitoring has to be more frequent, and NOx reduction must remain within a tighter tolerance level. As a result, initial feedback from Snowbirds who have contacted me indicates that 2013 diesel pickups are likely to register fault codes more frequently, and the process required to clear the codes is more complex.

For 2013, the distance which can be travelled after a DEF fault is triggered, and before “limp mode” (maximum speed 4mph) is initiated, gets accelerated, which can create a lot of stress for an owner. There is no doubt that it would be a very upsetting experience to see a message on the dash that your truck will be in limp mode in a few hundred miles or less, especially with the knowledge that it requires a regeneration to fully clear the SCR of sulfur compounds.

Unfortunately, there is no direct method an owner can use to force a regeneration, but feedback from an owner of a 2013 in Mexico this season has turned up what appears to be a very effective fix. The information provided indicates that EPA regulations require regenerations to occur more frequently, as much as twice as often, if there is a problem with the DPF pressure sensors, so disconnecting the power to the DPF sensors can force a regeneration.

How soon that regeneration happens depends on what distance has been travelled since the last regeneration. If more than half the normal distance between regenerations has already been travelled, the driver will immediately see a message advising that regeneration has started and to keep driving until it is finished, up to 30 minutes, at highway speed. If half the normal distance between regenerations has not yet been travelled, it could be anything up to a hundred miles before the regeneration triggers. Odds are though that for a fault condition to have occurred, it is very likely that more than half the normal distance since the last regeneration has already been travelled. I have seen this procedure used, and it did work, but it would be helpful to receive feedback from other owners of 2013 model year diesel pickups in Mexico about any problems they have experienced, and how they dealt with those problems.


Some owners of 2007.5 and later diesel pickups do promote the idea of removing all the emissions equipment and using a programmer to delete the DPF and SCR controls. This may have been a solution up until 2012, albeit a very expensive, and illegal, solution. As of the 2013 model year though, new regulations require that the vehicle ECM (on board computer) be locked . As a result, removal and deletion of the emissions equipment does not seem to be an option going forward.


In the longer term, the best solution for all Snowbirds would be for Mexico to introduce ultra low sulfur diesel throughout the country, as it has been promising to do for many years. In the meantime, owners of 2013 and later diesel pickups, if they decide to ignore warranty warnings and drive into Mexico, might be well advised to carry a large amount of ULSD fuel with them, so as to delay or eliminate the need to use Mexican diesel.

Ted White March 13, 2013 whitetmp@aol.com

Ted White has more than 5 years of experience with Diesel Particulate Filter (DPF) and Diesel Exhaust Fluid (DEF) related problems while in Mexico, and can assist owners, via email, to clear fault conditions by themselves. Anyone requiring information about how these modern diesel emissions systems work, and/or how to clear fault conditions while in Mexico, can contact Ted at whitetmp@aol.com

The Latest News/Update regarding Diesel Fuel on the Baja, Mexico

From: Ted White -- WHITETMP@aol.com

April 24, 2015

On April 4th of this year, 2015, while traveling north on the Baja, I collected a sample of the diesel fuel on sale at the Pemex station in El Rosario. This station is used by most, if not all, drivers heading south as it is just BEFORE the long desert haul down to Guerrero Negro. It is also commonly used for refueling on the way north again, as it is conveniently located AFTER the long desert haul.

Going south, the station is located at the bottom of a long, steep hill following a military inspection, and just prior to the 90 degrees left turn in Mex 1. The coordinates, for Google Earth or your GPS, are: N 30 03.600, W 115 43.533.

On the basis of some credible information I received about the diesel fuel being distributed in the northern part of the Baja, on April 6, 2015 I sent the diesel fuel sample from El Rosario to a testing laboratory in the USA.

Yesterday, April 23, 2015, I received the results from the lab. The fuel sample is Ultra Low Sulfur Diesel (ULSD, or UBA in Mexico) with 10 ppm sulfur content. In other words, it is most likely from the USA, or from Japan, where some of Mexico's diesel is apparently sourced, and was distributed from the Pemex Tank Farm at Ensenada.

Clearly, the results from a single sample taken on April 4, 2015 do not prove that the diesel at the Pemex in El Rosario is always ULSD, but the results do add credibility to the information I received about fuel distribution in the Baja. In addition, I have personally received emails from Pemex stating that the Northern Baja gets its diesel distributed from Mexicali (which implies USA origin) and Ensenada (which implies USA and/or Japanese origin), which supports the credible third party claim that all of the diesel in the Northern Baja is ULSD.

FYI, Pemex has confirmed to me in an email that all of the diesel in the Southern Baja (BCS) originates at refineries in Mexico and is distributed from La Paz. All of the diesel fuel in the Southern Baja can therefore be considered to be Low Sulfur Diesel (LSD) with sulfur content up to 500ppm. In other words, there is NO ULSD in the Southern Baja.

All of this gives good reason to believe that owners buying diesel at the El Rosario Pemex are most likely buying ULSD, and it also gives good reason to believe that diesel at all of the stations in the Northern Baja, including the one just before the border with the Southern Baja, are carrying ULSD.

Again, there are no guarantees, without regular sampling, but the test kit and lab analysis costs more than $100, so I'm not about to take up the testing of diesel fuel as a hobby. It is, however, my opinion at this time, that owners could assume with some confidence that the diesel fuel in the Northern Baja is ULSD, and could plan their refueling on this basis, so as to avoid temporary sulfur poisoning of the emissions system, and inconvenient fault codes, in 2011 and later vehicles.

Please share the contents of this email with other folks you may know of who are taking late model diesel powered vehicles in to the Baja.

Best Regards

Ed (Ted) White

By the way, there isn't much point in asking the attendants at Pemex stations whether they have ULSD, because they don't have any idea. They could say yes, or no, but it would mean nothing without something in writing on official Pemex documentation.


From: Ted White -- WHITETMP@aol.com

For almost 8 years I have been gathering data on the behavior of diesel pickups while in Mexico, where most of the diesel fuel is still LSD (Low Sulfur Diesel), up to 500 ppm. Unfortunately, ULSD (Ultr-Low-Sulfur-Diesel), 15 ppm, is available only in border cities/towns, the Northern Baja, Mexico City.

My present database (November 2015) contains detailed information about the effects of Mexican LSD on the emissions systems of Ford Power Strokes, Dodge RAMs, and GM Duramax from 2007.5 through the 2015 model years.

With respect to the Ford Power Stroke, the emissions systems for all model years up to and including 2014 have been very tolerant of the higher sulfur levels in Mexican fuel. I have reports of engine lights on occasionally for varying lengths of time, but no reports of any truck entering speed limitation. All of that changed earlier this year, and that is why I am doing this post. Owners of 2015 Powerstrokes, planning to take them in to Mexico for the Snowbird season, need to read the following:

In January of 2015 the owner of a 2015 Ford F350 Power Stroke joined a caravan tour into the Baja. As expected, his truck exhibited NO symptoms of temporary sulfur poisoning of the emissions system while he was towing his fifth wheel trailer. This is because towing a heavy trailer, or carrying a camper in the truck bed, provides sufficient load to keep exhaust gas temperatures elevated high enough to prevent the deposit of sulfur compounds in the emissions system. (This is also true for late model Dodge and GM diesel powered pickups).

In this specific case though, the owner left the caravan while in the Los Cabos area and traveled to La Paz, where he booked in to an RV park, unhooked his trailer, and began driving the truck with no tow load. Within a week or so, his truck went in to speed limitation, and eventually limp mode. He contacted the local Ford dealer in La Paz and discovered that there is NO ability to service late model Ford Powerstrokes in Mexico. He then contacted a dealership in the U.S., which canceled his warranty when it was discovered that he was in Mexico.

At that stage he researched the problem on line and contacted me, but it was too late to assist due to the truck being in limp mode. The only way to clear the sulfur compounds from the emissions system, and return the truck to normal operation, would be to run a Service Regeneration.

This owner then made the decision to import a delete kit in to Mexico, and within two weeks he had removed the entire factory emissions system and installed the delete kit, at which point he was able to get the truck running normally again.

The HUGE problem with this case, is that there is no way to know whether this single owner's experience is indicative of a larger 2015 model year issue that will affect other owners driving on Mexican diesel, or whether his truck suffered a completely unrelated emissions system component failure that put his truck in to limp mode.

Erring on the side of caution I decided to do this posting, and to make a recommendation based on my extensive experience with similar problems on GM duramax post-2012 models. In conjunction with a 2015 Ford Powerstroke owner, I have confirmed that the latest model Edge Tuner CT2, can force a regeneration on the 2015 Powerstroke. I am therefore recommending that any 2015 Powerstroke owner planning to drive in Mexico using Mexican diesel should purchase and carry an Edge CT2 Tuner. (During the purchase, owners should confirm that the CT2 they are buying can initiate a regeneration cycle, and PLEASE NOTE that I do not work for Edge and I receive no compensation for this recommendation).

Once in Mexico, if or when the engine light or other DEF or emissions related message shows, a regeneration should be initiated, especially if there is warning of speed limitation. Following the regeneration, NOX emissions can be expected to return to normal range for long enough to cancel the emissions fault codes. If the Power Stroke behaves under these conditions the same as the GM Duramax post-2013, the engine light could remain on for up to 30 miles and/or three engine warm-ups, but will extinguish by itself.

Please note that I have insufficient information at this time to accurately describe the process because it is presently at the stage of a “Beta Test”. I would have preferred to witness the process myself on a 2015 Power Stroke in Mexico but that hasn't been possible to do so. For this reason, it would be of great assistance to me, and to owners of late model Power Strokes, if owners could share their Mexico experiences this season if they have 2015 or later vehicles. There is every reason to believe, based on extensive observation of 2013 and later Duramax powered trucks, that the Edge CT2 will, via its regeneration function, will similarly prevent any major sulfur-in-fuel problem from developing, but I need further confirmation before becoming 100% confident.

Feel free to contact me if you have additional information, either via a private message, or directly to whitetmp@aol.com

last updated 12/8/2015 craig@geekami.com