While I was working in the commercial diesel truck industry I was able to attend several meetings over a 12-24 month conducted by 3 of the major US truck diesel manufacturers and one import ( Cum, Cat, Int, and Hino ). The general consensus was that fuel economy would drop by about 3%. This was about the time of the ULSD changeover. I am now retired and so have no updated info. However my SDL fuel economy has dropped from about 26.5 mpg to just under or close to 25 mpg over many, many tank fills.

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Paul 1987 300 SDL; 2000 ML; '69 MGB; '68 VW Fastback

Some of the difference you seeing Paul, could maybe be attributed to a small percentage of Bio Diesel being blended into the Fuel. I think they can go up to 5% without labeling it as Bio blend IIRC. Combined with a 2-3% loss (if we agree that could occur) you could get another percent or two maybe out of Bio Blend? Might be something else too... probably several variables together here giving you a drop?

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1983 300D-Turbo - Deep Blue w Palomino MB Tex (total loss in fire 1/5/09 RIP)
1995 E320 W124 Polar White/Grey Mushroom MB Tex
2005 F150 Supercrew - Arizona Beige - Lear topper
1985 Piaggio Vespa T5 - Black and Chrome

www.cphilip.com

I have been noticing the same thing; back in 2004 when I first got my SDL the mileage was a rock steady 23.5. Now on this last tank I'm down to 20.5.

My driving hasn't changed and the car is in better shape now, so?

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2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200

No one seems to talk about the loss of sulphur in the fuel. In the '70's I was told one reason for the crankcase oil change is to get rid of the sulphur that was placed there as part of the combustion process. The warnings were particularly strong for engines with short running periods, where some water vapor may be left in the crankcase. This would combine with the sulphur to make sulphuric acid, which would then go after all the internal parts.

It is maybe just wishful thinking on my part, but in my Cummins engine with 300+K miles, the oil I change after 3,000 miles seems cleaner than in the early '90's when sulphur had not been removed from the fuel.

Even on my '71 220D, the oil does seem cleaner than in '74 with my then new 240D. Is this just my imagination?

Ron

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1971 220D, daily driver, new paint, 142K
1973 220D, low compression
1975 300D, back on the road! 166K
1971 220D, salvage, rear hit, engine excellent
1972 250, bad cam, but runs!
1971 230, engine stuck
1971 220D, low compression, rusty
1976 240D, salvage, engine excellent
1966 230SL, water in oil after rebuild

I accept your general comments. It was just interesting that my mileage dropped as soon as I filled with ULSD. And now I have different tires, another variable. But my mileage did drop before the tire change. Also, my mileage was and is rock steady as Hatterasguy sald. My drop is over 4%, however.

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Paul 1987 300 SDL; 2000 ML; '69 MGB; '68 VW Fastback

Sulfur is not put into the fuel, it is a natural part of diesel oil and has no benefit to the injection system, engine or combustion.

The process of removing the sulfur is what reduces lubricity, the loss of sulfur itself makes no difference.

You are correct about the relationship between the sulphur in diesel fuel and acids in engine oil. That's also why the TBN of oils has been on a downward trend as less base is needed to counteract the acids when burning low or ultra-low sulphur diesel. Another advantage of ULSD is minimal SOx emissions which contribute to acid rain. Some also say ULSD leads to less carbon buildup in the intake. I'm not sure if that's true, but I'll buy that for a dollar.

Again I can't say that I've noticed a drop in mileage with ULSD but it's worth noting that I always additize my fuel with something that boosts cetane and lubricity and cleans injectors.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

Actually I think my mileage might have improved slightly with the ULSD. Since I have an 85 cali car my Ox cat doesn't plug up as much due to lower soot emissions. Its hard to say because I have made progressive improvements to my car that have upped the mileage. The lower chemical energy content due to the drop in sulfur content is partially offset by the more complete burn of the fuel.

2% seems like a reasonable figure. If anything is causing a drop in mileage I would put money on the refiners cutting the fuel to make more money off these outrageous diesel prices.

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green 85 300SD 200K miles "Das Schlepper Frog" With a OM603 TBO360 turbo ( To be intercooled someday )( Kalifornistani emissons )
white 79 300SD 200K'ish miles "Farfegnugen" (RIP - cracked crank)
desert storm primer 63 T-bird "The Undead" (long term hibernation)

http://ecomodder.com/forum/fe-graphs/sig692a.png

I wonder what in the world they would cut the fuel with? It seems that any kind of dilluter would cost close to what oil would cost. What could they be cutting it with ?
I too am seeing a pretty obvious drop in mpgs on my wifes 97 e300d in the last 6 months. I thought it was her driving style but her style hasnt changed within the last 6 months. We were getting 30 plus on average 6 or 7 months ago but are averaging 24 to 25 now. But my 85 is still getting 25-26 mpg all day. I dont know. I maintain them very well. Jim

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1997 E300D Wife's daily driver
1985 300SD my daily driver
1999 Expedition family road trip and material hauler

My mileage has been all over the place.

There was a time, pre-2004, when I would never get less than 26.5 mpg in New England winters no matter HOW I drove. And 29 - 31 mpg was average for summer driving (I have pretty favorable driving conditions).

Using the same driving techniques as used in the past (1/2 pedal from every stop, easing off as I approached 10 mph + the legal limit), I will get as low as18 mpg in the winter. 23 - 25 mpg in the summer, now. If I drive gingerly, I can notch it up to 30 mpg (I'm talking about 55 mph on flat surfaces).

That said, for some reason I used to have "peppy-good-mileage" diesel fuel and "lousy-poor-mileage" diesel fuel. Now, all fuel seems "medium pep, lousy mileage" diesel fuel.

I'd rather spell things out in Layman's than divulge in the details as was presented in the preceding observation.

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1987 300SDL (324000)

1986 Porsche 951 (944 Turbo) (166000)

1978 Porsche 924 (99000)

1996 Nissan Pathfinder R50 (201000)

Forced,

What do U think the lubricity of the sulphur does? It makes injection pumps (IP) last longer.

The new Diesel engines without IP don't need sulphur in the fuel, but it helps older IP last longer.

P E H

Incorrect, Sulfur has no lubricity qualities.

The process that removes the sulfur is what alters lubricity.

Forced is correct, the sulfur itself does nothing. The reduced lubricity is a side-effect of the process used to remove the sulfur. The lubricity is restored to the ASTM standards (with additives) before you buy it. If you don't think that standard is sufficient you can always use additional additives.

I had a CAT 3208 eat an injection pump after LSD came out, cost me $4500 and two days downtime at Camp Caterpillar. I have run RedLine Diesel Fuel Catalyst 1oz/10gallons in all diesels since. I don't know that it's necessary, nor that it fixes everything, but I don't trust the refineries to ensure the lubricity of my fuel any more.

Some of us say no additives, some of us have our favorites. It's like the synthetic vs dino oil threads, it might be better but is it necessary. Bad additives can certainly be worse in both cases.

If you decide you want to run a fuel additive, pick one that is NOT solvent based, most are solvent based "cleaners". Solvents will mess with seals and can cause other problems.

Fuel BTUs / calories have certainly decreased somewhat, Cetane I'm not sure, but I don't seem to be able to get the fuel mileage that I once did, in several vehicles. Could be other factors, I don't know. The available fuel is what it is though, so I do the best I can to get reasonable power and mileage while protecting my engines and not messing them up with miracle additives and goofy experimental fueling.

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Gone to the dark side

- Jeff

I have noticed no reduction in fuel economy from the change in diesel fuel.

Tom W

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.