Mixing LOW Sulpher w. ULTRA LOW

[Chickadee]

G'morning Newmar Gang: Have a question... Our rig runs a 500 Cummins ISM model yr. 2008. Supposed to use ULSD. If ya wanted to "top off" your fuel tank which is 3/4 full of ULSD, and could only conveniently find pumps labled "Low Sulphur Highway Diesel" (LSD), could you safely get by adding a 1/4 tank of LSD? Have read previous threads re: ULSD and LSD but is an occasional (very rare) mixing o.k.?? Thanks. Steve

[Chickadee]

G'morning Newmar Gang: Have a question... Our rig runs a 500 Cummins ISM model yr. 2008. Supposed to use ULSD. If ya wanted to "top off" your fuel tank which is 3/4 full of ULSD, and could only conveniently find pumps labled "Low Sulphur Highway Diesel" (LSD), could you safely get by adding a 1/4 tank of LSD? Have read previous threads re: ULSD and LSD but is an occasional (very rare) mixing o.k.?? Thanks. Steve

[69RoadRunner]

Unless the station is a very low volume station, it should have ULSD.

It might not be certified yet as being ULSD, but you should be getting ULSD.

They've only been delivering ULSD to stations since late 2006, IIRC. Obviously, they fill the tank before it is empty, so LSD mixes with ULSD (be careful of the brown acid!) for a while.

Eventually all of the LSD is gone, but the station has to be tested and certified to put the ULSD label on the pump.

I've heard that some don't want the ULSD label because people will think they're getting LSD, which gives better mileage and performance for diesel engines that can handle LSD.

The bottom line is, if you want to be safe, stick with ULSD. However, 1/4 tank of LSD TODAY won't kill your engine.

But, if you have 3/4 of a tank, you are not in an emergency situation. You have time to get to a ULSD station.

[GaryKD]

For me, I would not do it.

I do not know how much or how frequent LSD use will be needed to cause deterioration or failure of the burner supported regeneration. However, it would need to be an emergency situation for me to add LSD to a ULSD designated fuel system. We have a bunch of $s invested in our coaches.

Not that anyone would catch one for doing it, I think it is illegal to put LSD in a fuel system labeled for ULSD fuel only.

[afrank1971]

For what it's worth, RVDude wrote:

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> ... burning LSD in a particulate filter equipped engine will only shorten the 200,000-300,000 mile estimated filter refurbish cycle time - no other damage will occur! </div></BLOCKQUOTE>

My understanding is that in the event you have reason to burn LSD instead of ULSD, it is illegal, but will cause no damage other than shortening the life span of the particulate filter. However, my knowledge is second hand, might be worth inquiring directly with RVDude who seems to know more about it. Good luck.

[RVDude]

chick:
Your 2008 ISM does NOT have a particulate filter. Burn all the LSD or ULSD or any mix your heart wants. Even farm grade (I don't mean bio) and #2 heating oil. Yep, Mexico is also in your rigs capabilities (little ULSD there). My understanding is that the ISM is EPA certified as is (no particulate filter) until 2010. Law, not engine design, requires that the ULSD label be on ALL 2007+ diesel engines.

And yes for those that do have the particulate filter the quote above is accurate. A CAT engineer told me even if you ran only LSD in a particulate filter equipped engine the only issue is the filter refurbish cycle time drops to 50,000 miles or so.

69rr is also very correct in that in some (lower48) stations it may take months to years before they get "certified" but they are still pumping only ULSD in the lower 48. The station's tanks need to be flushed for a period of time before they are sulpher free enough to test correctly for ULSD.

More chemistry - LSD contains far more cylinder lubricants than ULSD. The only difference in the fuels is emissions - the burning of sulpher forms that black soot diesels spew out. ULSD has little sulpher and the particulate filter removes the rest of the soot. That's all it does.

[GaryKD]

Thanks RVDude

[porscheracer]

A few '08 engines, specifically the '08 MB 3.0L V6 (Sprinter chassis), DO require ULSD. It even has a sticker that specifically says DO NOT use biodiesel!!

[cb5300]

My '08 ISX requires ULSD, got a label stating so.

[RVDude]

porsche: Actually MOST 2008 engines HAVE a particulate filter. The Cummins ISM does NOT.

cd5300: As said before, all 2007+ WILL have a label (legal mandate by EPA) that says ULSD only. If you have a Cummins ISM it does NOT have a particulate filter and CAN burn LSD w/o any engineering issue even though (by law) it has a ULSD sticker. The ISX HAS a particulate filter and to minimize your operating costs (i.e. filter recycle time) burn ULSD only.

As I try to keep clear, there is a difference in "legal" requirement and "engineering" requirement where the engineering is predicated only on if you have a particulate filter.

In my post above I clarified "farm grade" to mean "off road" diesel not BIO-diesel. The distinction here is road taxes and potentially even more sulpher than LSD. You MUST verify use of BIO and to what percent by your specific engine manufacturer and engine type before using BIO-diesel.

[Spikester]

Right on RVDude, as usual, Thanks.

Out of curiosity I inquired as to the cost of replacing a particulate filter for an ISB engine, believe me you do not want to know the cost, or do anything to shorten its life cycle if possible, it is a really EXPENSIVE proposition!

Its kinda nice to have an exhaust extension that almost as shiny on the inside as the outside, no soot build up after 11K miles. Still waiting for that first regen cycle, really curious about the effects, if any, of the extremely high exhaust temperatures.

Thanks again.
Spike

[RustyJC]

The lower sulfur levels in ULSD do not directly result in lower lubricity since the sulfur is not a lubricant. Rather, the additional refining required to reduce sulfur content removes aromatics that provide lubricating qualities. Chevron's comments on this subject are:

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Lubricity:

Lubricity is a measure of the fuel's ability to lubricate and protect the various parts of the engine's fuel injection system from wear. The processing required to reduce sulfur to 15 ppm also removes naturally-occurring lubricity agents in diesel fuel. To manage this change the American Society for Testing and Materials (ASTM) adopted the lubricity specification defined in ASTM D975 for all diesel fuels and this standard went into effect January 1, 2005.

The D975 specification is based on the High Frequency Reciprocating Rig (HFRR) test (D 6079) and requires a wear scar no larger than 520 microns. </div></BLOCKQUOTE>

Rusty

[Eddie Foy]

The only thing it could hurt is the particulate filter. Very occassional use will not cause a problem.



<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Chickadee:
G'morning Newmar Gang: Have a question... Our rig runs a 500 Cummins ISM model yr. 2008. Supposed to use ULSD. If ya wanted to "top off" your fuel tank which is 3/4 full of ULSD, and could only conveniently find pumps labled "Low Sulphur Highway Diesel" (LSD), could you safely get by adding a 1/4 tank of LSD? Have read previous threads re: ULSD and LSD but is an occasional (very rare) mixing o.k.?? Thanks. Steve </div></BLOCKQUOTE>

[Ray,IN]

I wonder how the folks traveling into Mexico deal with this issue since ULSD is not available there.