Low sulfur fuel: a hinge that creates opportunity?

[ltslimjim]

Just reading something a lot are already aware of relatively speaking, and curiosity has the better of me.

Quote:
TBN (Total Base Number) additives in the lubricant protect against high levels of sulfur content in fuel. It is important to know the sulfur content of the fuel because over-inhibiting with high TBN lubricants will result in premature deposit formation.


Source:

http://www.spectroinc.com/analytical-tests-sulfur-content.htm

So, does typical e-10 gasoline have higher sulfur in the US compared to other parts of the world like western Europe?

Is this hurting some apps concerning ability to extend intervals 'safely', on fuel alone?

OR is this more of an issue in diesels so that doesn't translate to gasoline fueled vehicles as directly? Their needs for soot control(deposit??) and relative need to go by soot/TAN values and not TBN retention for their OCI?

 

[MNgopher]

Gasoline in the US is presently at Tier II levels of Sulfur, with an average of 30ppm. That was enacted by the EPA in 1999. There us talk of going to Tier III, which would be a 10ppm average. Gasoline in Europe is already Tier III as of 2009.

On-road diesel in the US is now at 15ppm average. Prior to about 2007, on-road was allowed up to 500ppm. Diesel is generally comparable in sulfur content now between the US and Europe.

 

[NHGUY]

Irving oil,on the east coast,once bragged in ads that its fuels had reduced sulphur content.Obviously a nod to trying to win over the tree hugging consumer to its pumps rather than someone elses.

 

[slo town]

California already limits sulfur in gasoline to 10PPM.

Scott

 

[ltslimjim]

Okay, that helps a lot. So much for that theory.

It was most strange to me to see the description of the relationship between sulfur in fuels to TBN.

 

[edhackett]

Sulfur reacts in the combustion process to form sulfuric acid. The acid makes its way into the crank case via blow-by. True for both gasoline and diesel.

Ed

 

[ltslimjim]

So, aside from being in engine oil itself(not actual sulfuric acid in virgin oil right? lol), then with the supposed move to 'lower' sulfur fuels, is sulfuric acid forming as a byproduct of combustion alone; regardless of how much native sulfur is remaining in fuels or not?

 

[edhackett]

Not sure exactly what you are asking, but here goes...

Formation of H2SO4 as a result of combustion of sulfur containing fuel is the major contributor on a vehicle operated under normal conditions(fully warmed up). The sulfur native in the oil, both in the base stock and additive package, contributes due to oil getting past the rings.

Moisture and other combustion products in the oil can react directly with the sulfur native to the oil to create acids. Moisture also reacts with NOx compounds formed in the combustion process forming nitric acid. That's one reason you see short tripped cars deplete TBN faster.

Ed

 

[ltslimjim]

^That's what I was getting at, but I didn't know which part of the process caused what. I'm trying to learn more about what's happening chemically and the various elements which come into play.

I mean, what IS 10 ppm of sulfur in 'Tier III' fuels compared to 30 ppm of sulfur in 'Tier II' fuels? It seems like comparing 'noise' and minimal, when both seem insignificant in those amounts which the 2nd post here outlines.

On the other hand, is that where QC and top-tier become more stringent on 'actually' getting those 'lower' numbers?

 

[Shannow]

Acids and acid gasses are formed during combustion...more sulfur, more sulfuric acid. Nitric oxides, nitric acid, CO2 and water carbonic acid.

Next bit is way oversimplified, but I hope hat it helps.

TBN is milligrammes per gramme of reserve alkalinity in the engine oil. Regardless of the species, it's all boiled down to how many mg of KOH (Potassium Hydroxide) would absorb the same amount of acid as the oil could.

Take my nissan, it starts with a fixed sump volume at oil change of just over 7 litres, (say) 6,0000 grammes, and say there's 10mg alkalinity per gramme (say) 6 grammes of KOH equivalent.

which could neutralise 3.8G of Hydrochloric acid, or 5.25g of sulfuric acid.

If I use 1000L (say 900,000g) of diesel in an oil change, and it's 10ppm sulfur, that's 9 grammes of sulfur that passes through the engine for that OCI, or about 3g of sulfuric acid formed.

Obviously most of it heads out the exhaust, but some ends up in the sump through blowby etc. etc., and it has to be added to the other stuff.

Make it 20ppm, and there's 6g of sulfuric acid formed, 30ppm and 9g.

Diesel used to be the bit that was left over, and therefore had a lot of "leftover" sulfur, and needed heaps of alkalinity in the oil to combat it.

low sulfur fuels, lower NOx etc. in the blowby gasses need less TBN...heck, less blowby needs less TBN...less oil consumption and cat damage allows higher TBN and additive levels in general

 

[Shannow]

Originally Posted By: NHGUY
Irving oil,on the east coast,once bragged in ads that its fuels had reduced sulphur content.Obviously a nod to trying to win over the tree hugging consumer to its pumps rather than someone elses.


Reduced sulfur (it's spelled with an f these days, much to my disappointment) has nothing to do with tree hugging, and much to do with how long do you want your limestone and concrete to last...may be advertised as green, but what do they do with the sulfur ?

There's mountains of the stuff, and not the mountains that third world children climb to grab volcanic sulfur to bring to market.

Sulfur taken out of fuel is a saleable commodity, that offsets other stuff, and is burned notin your cities.

 

[BMWTurboDzl]

It is my understanding low sulphur revolves around emissions. Low sulphur allows for cleaner burning fuel which allows for the use of low ash oils which allow for more efficient emissions (low ash oils won't poison cats and clog DPFs).

 

[MNgopher]

Low sulphur does revolve aroud emissions. There is the direct emissions and then their is the impact of sulphur on other pollution control devices that necessitate its lowering and removal from fuels.

The suplhur removed does have industrial uses (acids, fertilizers, etc...), but the cost of removing it from the fuels is high. In addition, the capital costs make it so refiners in north america generally don't remove it unless mandated to do so.

 

[ltslimjim]

@Shannow, Thus the potential for high consumption vehicles to foul cats, especially if there is the decision to use HDEO which may effectively nuke an old cat in those conditions of high sulfur/high TBN/high consumption?

I suppose it boils down to the engine/app in question and it's internal conditions/setup more so than the fuels used which leads to nuking of TBN.

So, could combating the issue of acids in an engine with 'too much' TBN lead to worse emissions to the point of failing without a failed component itself?

 

[artificialist]

I have a hard time believing there can be too much TBN and too little sulfur, because if you look at a used oil analysis of a gasoline engine filled with Shell Rotella T Synthetic, it is always impressive, even if CH-4 or CI-4 Plus versions were used.

 

[ltslimjim]

^That's what I thought. It seemed really strange and I don't know why I took it as translating to that degree, just odd testing description by the site/company quoted in the OP.