Sulfur in Fuels detrimental?

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Jul 24, 2002
Quebec, Canada
Are sulfur in gasoline detrimental in our engines if it weren't for motor oil to protect it?

If so, then what can sulfur do/damage in the engine, what additive in motor oils actually fight this off?

I've always been under the assumption that heavy amounts of sulfur is more of an environmental issure than a engine reliability risk.

Thanks for the input,

I think there was an article in the Toronto Star about how Esso contains more sulfur than all the other gas stations, but that it's not harmful to the engine, it's just harmful to the environment. I noticed a good amount of sulfur on my last oil analysis, and I use Esso gas.
Yes, I've read this a while back Patman. I've stopped using Esso primarily for that reason. They have not taken the time to renovate their refinery plants.

Unfortunately, for us Quebec residents, Sunoco is no longer available here (replaced by Ultra-Mar). So, based on reports from the net, and the DSM board, I'm "forced" to use Petro Canada fuels.

I get tickled-pink everytime I fill-up with Sunoco (Canadian version only, US stations operate differently I think), as I know they are the cleanest fuels in Canada.

Patman, did the sulfur (in your oil analysis reports) indicate more wear or more oil degradation? Thanks.



Originally posted by The_Oz:

Patman, did the sulfur (in your oil analysis reports) indicate more wear or more oil degradation?

I'm honestly not sure. I think Terry is best equipped to handle this question.

I beleive it did contribute to the higher oxidation levels that you had.

Sulfur is a great lubricant that is used as such in a lot of cases. The problem is that when burned it turns into a sulfuric acid which carbonizes up and then creates hot spots as well as seeps past the rings, causing the oil's tbn to be reduced a little faster than if not there.

In diesel engines where sulfur is common in their fuel, this is true and why a TBN count is more desirable vs a car which gas has minimal amounts in most cases.

That is why in my fuel test videos you'll see me using actual sufuric acids to see how a fuel additive will neutralize it as this will help the oil from having to become depleted as much.

As for the damage, I beleive that what happens most is carbon builds up in the cyl's, cause valve wear reccession, could cause sticking valves,in diesels glow plugs become heat sinked to the head therefore not able to produce the preheat for easy starting and such. It also introduces more acidity to the oil reducing oil's ability to extend drain intervals.

As for metal wear and such I'm not sure that the sulfur itself would cause a problem here because I know it has and still is being used in off road diesel fuels and this does provide lubrication for the seals. When Gore had reduced the sulfur in OTR diesel fuels, a lot of diesel engines began to have seal/pump failures due to the lack of lubrication that was provided by the fuel which now has been rectified by manufactures.

This is one primary reason I strongly use our neutra 131 to eliminate any possible problems due to this. I can take the neutra and drop sulfuric acid directly in it and it instantly neutralizes the sulfuric acid. This is another reason for using this when changing over oils where the previous oil may not have been able to maintain acid neutralization, the 131 will provide this and then the new oil won't come back deplete prematurely having to work overtime cleaning up from the previous oils lack of ability to keep acids in check.

I suspect I just opened up a new bucket of worms here but hopefully helps explain more on the cause and effects of sulfur.

[ July 31, 2002, 10:10 AM: Message edited by: BOBISTHEOILGUY ]
The sulfur reading in a gasoline engine is not as meaningful as a diesel powered one.

For one gasoline contains less sulfur than diesel fuel. It is true as Bob said that it may contribute to oxidation as in cleaning. Also it is a lubricant for fuel side components. The diesel engine pushes more of the fuel residue by the rings and seals primarily because of increased compression pressure.

I provide the sulfur reading as a free extra for the gasoline customer but I would not put alot of stock in its importance. The most important aspect in trending analysis is to look at levels over time on a relative basis. Especially if the fuel dilution reading is negative or trace.

The gasoline fuel problem I am most concerned about is the lack of solvency by decreased "lighter "parts of the formulation. The fuel becomes "stale" faster than ever before and has decreased energy value,gums up fuel delivery systems, and does not contribute to a clean oil side as in the past.
I am not a fuel expert but a clean tight running engine will keep the oil in better shape than the opposite. The higher oxidation and nitration readings that the GM V8 folks see is the fact that the engine is relatively large ( burns alot of gas), most drive them hard, and the fuel quality isn't what it used to be.
The jury is still out on good fuel additives, if Schaeffers 131 is as good as their oils it would be a candidate for use. I am looking at it in my own cars now. TK7 was a highly recommended fuel add but I can't find it anymore. I am testing a custom designed product and will share that here when testing is finished at a later date.

Originally posted by Patman:
I noticed a good amount of sulfur on my last oil analysis, and I use Esso gas.

Patman, maybe we need to re-evaluate the MaxLife oxidation and TBN numbers from your oil analysis!
This extra sulfur certainly could throw a bit of a wrench into my plans on doing longer drain intervals.

However, all CDN gas companies are supposed to reduce their sulfur levels soon. I should probably stick with Esso and see how the analysis results change once Esso lowers their sulfur content. I don't have much choice when it comes to gas, Shell up here is only 91 octane, same with Petro Canada. And Sunoco has ethanol and nets me 2-3 MPG less, plus their 94 octane is more expensive, and their stations are out of the way for me. Esso is perfect because it's got enough octane for daily driving in the summer here (92 octane) plus I have a Speedpass and that also gets me at least 30-40 free car washes a year! (which I use up like crazy in the winter months!)
The US is also lowering sulfur in fuels. It's still a year or so away and they are phasing it in slowly so the refiners can make the adjustments and add new equipment as needed.
"Gasoline Sulfur Standards
Beginning in 2004, the nation's refiners and importers of gasoline will have the flexibility to manufacture gasoline with a range of sulfur levels as long as all of their production is capped at 300 parts per million (ppm) and their annual corporate average sulfur levels are 120 ppm. In 2005, the refinery average will be set at 30 ppm, with a corporate average of 90 ppm and a cap of 300 ppm. Both of the average standards can be met with use of credits generated by other refiners who reduce sulfur levels early. Finally, in 2006, refiners will meet a 30 ppm average sulfur level with a maximum cap of 80 ppm. Gasoline produced for sale in parts of the Western U.S. will be allowed to meet a 150 ppm refinery average and a 300 ppm cap through 2006 but will have to meet the 30 ppm average/80 ppm cap by 2007.

Small refiners (those who employ no more than 1,500 employees and have a corporate crude oil capacity of no more than 155,000 barrels per day) will be able to comply with less stringent interim standards through 2007, when they must meet the final sulfur standards. If necessary, small refiners that demonstrate a severe economic hardship can apply for an additional extension of up to two years.
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