Using 40 or 42 cetane fuel we get 12/13 mpg city driving. Basically the same using power servce(white) at .5 ounce/gallon. Highway driving with little traffic at 65 or so mph we get 18 to 21 using power service. Grades we encounter correlate with mileage. We always use dfa before a long trip. Fuel burn is actual, not computer generated by truck. I'm satisfied with the mileage,past experience with the 5.8 1995 is 8-10mpg city driving and no more than 15 mpg highway @ no more than 60 mph(3.55 rear)F250 standard cab 8'box weighing 5,800lb on a scale. Current truck is a 2003 F350 crew cab 6.0 shortie, 3.73 rear, weighing just under 7,400lb with me in it.(and I don't weight 1,600 lbs) I'll take those numbers.

 

The 6.0Ls are 18.5:1 compression ratio. I run Stanadyne Performance Formula 8 oz to 30 gallons. It runs fine and I get about 16 around town +/- depending on traffic. I get 19-20 on the road depending on terrain and weather, mainly wind.

 

I was in NAPA and got a new "white" bottle of Powerservice. First time I really noticed the cetane boost number of 4. I also saw the silver bottle that has a cetane boost number of 6. Gota ask, curious, how much is really gained going from a 4 to a 6. Might have to try the silver bottle next.

 

I would say that it would be about a cetane rating of 2 more . HA HA HA !! sorry could'nt resist . The engineers say a cetane rating of 48 is what the 6.0 likes . So I guess it depends on the rating that the fuel has you use . If its rating is 42 and you use the 4 your 2 short . So the 6 boost would get you to the 48 rating ??? Probally not much difference in my opinion .

 

I recall my service writer saying we have a cetane rating of 45/46 in AZ and that all the 6.0s in the area aren't burning the best fuel.

I mentioned that my truck "seems" to run better when I fillup in Eloy @ Flying J and he said their fuel is as low as everyone elses.

I know running a supercharged gas motor on less than premium is bad. I wonder how much affect there is on our diesels?

 

I run the white bottles in the winter and the silver bottles in the summer. The silver bottle (Diesel Kleen) does not have any anit-gel properties. The max cetane boost levels are when mixed at maximum concentration of 0.64 oz. of additive to 1 gallon of fuel. The 96 oz. bottle will treat 150 gallons of fuel when mixed at this ratio.

I don't know if going from 4 to 6 really offers any benefit, but when the silver bottle is the same price as the white bottle (and I don't need any cold weather protection), I run the Diesel Kleen for max cetane boost.

 

I have an 05 6.0 work truck and use the power service silver bottle sometimes. I get 1/2 mile mpg better, and I use 16 ounces to a 40 gallon tank. I do see a noticeable increase in power, and can tell when I forget to add it. I get 12.5 mpg's with a van that wieghs 10,000 lbs, so I guess that is o.k., but motor only has 6700 miles on it and I hope it improves but I doubt it will.

 

Thanks Twin. Wont use the silver in the winter. Will give it a try this summer and see if there is any difference.

 

Hey Mark ,

From everything I have been reading on the 6.0 is that they do improve in mileage as they break in . Some even say it takes 12,000 mile .
I think I may try some cetane boost . You guys got me curious now .

 

Ok, Kero in your fuel added . Think about it !!!

Don

 

I have been reading these threads about bad MPG's and have to wonder where they but their fuel and if the people who get bad gas mileage are fueling up at a discount gas station. Just a thought.

 

2. Diesel Fuel and Driving Performance

Starting
Power
Noise
Fuel Economy

Wear
Low Temperature Operability
Filter Life – Fuel Stability
Emissions


There are a number of engine performance characteristics that are generally recognized as important. Their relative importance depends on engine type and duty cycle (truck, passenger car, stationary generator, marine vessel, etc.).


starting ease
sufficient power
low noise
good fuel economy

low wear (lubricity)
low temperature operability
long filter life (stability)
low emissions

Engine design, by far and away, has the greatest impact on most of these characteristics. But since the focus of this publication is fuel, this chapter will discuss how they are affected by fuel properties.

STARTING
When a cold diesel engine is started (cold start), the heat of compression is the only energy source available to heat the gas in the combustion chamber to a temperature that will initiate the spontaneous combustion of the fuel (about 750°F [400°C]). Since the walls of the combustion chamber are initially at ambient temperature rather than operating temperature, they are a significant heat sink rather than a heat source. And since cranking speed is slower than operating speed, compression is also slower, which allows more time for the compressed air to lose heat to the chamber walls. (A glow plug provides an additional source of heat in indirect-injection diesel engines.)

A fuel that combusts more readily will require less cranking to start an engine. Thus, if other conditions are equal, a higher cetane number fuel makes starting easier. As the compression temperature is reduced by variables like lower compression pressure, lower ambient temperature, and lower coolant temperature, an engine requires an increasingly higher cetane number fuel to start easily. Research indicates that fuels meeting the ASTM Standard Specification D 975 cetane number requirement of a minimum of 40 provide adequate cold starting performance in modern diesel engines. At temperatures below freezing, starting aids may be necessary regardless of the cetane number of the fuel.

Even after the engine has started, the temperatures in the combustion chamber may still be too low to induce complete combustion of the injected fuel. The resulting unburned and partially burned fuel is exhausted as a mist of small droplets that is seen as white smoke (cold smoke). This situation normally lasts for less than a minute, but the exhaust is irritating to the eyes, and can be objectionable if a number of vehicles are started together in an enclosed space. A fuel with a higher cetane number can ameliorate the problem by shortening the time during which unburned fuel is emitted to the atmosphere.

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CETANE NUMBER
Cetane Number is a measure of how readily the fuel starts to burn (autoignites) under diesel engine conditions. A fuel with a high cetane number starts to burn shortly after it is injected into the cylinder; it has a short ignition delay period. Conversely, a fuel with a low cetane number resists autoignition and has a longer ignition delay period. (See Chapter 5 for more information about measuring cetane number.) Although the cetane number of a fuel is assumed to predict its ignition delay in any engine, the actual delay represented by the cetane number is valid only for the single cylinder engine in which it was measured. The fuel's performance in other engines may differ.
A fuel's ignition delay is determined by its chemistry. In a warm engine, the delay is independent of the physical characteristics of the fuel, like volatility and viscosity. (The cetane index correlations utilize density and distillation temperature properties to estimate cetane number, but these properties are being used as indirect indicators of fuel chemistry, not as direct variables.)
Cetane numbers apply only to distillate fuels; they are not measured for fuels containing petroleum resid (marine fuels).

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POWER
Power is determined by engine design. Diesel engines are rated at the brake horsepower developed at the smoke limit.1 For a given engine, varying fuel properties within the ASTM D 975 specification range (see Figure 5-2) does not alter power significantly. For example, in one study seven fuels with varying distillation profiles and aromatics contents were tested in three engines. In each engine, power at peak torque and at rated speed (at full load) for the seven fuels was relatively constant. However, if fuel viscosity is outside of the D 975 specification range, combustion may be poor, resulting in loss of power and fuel economy.

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NOISE
The noise produced by a diesel engine is a combination of combustion noise and mechanical noise. Fuel properties can affect only combustion noise.

In a diesel engine, the fuel ignites spontaneously shortly after injection begins. During this delay, the fuel is vaporizing and mixing with the air in the combustion chamber. Combustion causes a rapid heat release and a rapid rise of combustion chamber pressure. The rapid pressure rise is responsible for the diesel knock that is very audible for some diesel engines.

Increasing the cetane number of the fuel can decrease the amount of knock by shortening the ignition delay. Less fuel has been injected by the time combustion begins and it has had less time to mix with air. As a result, the rapid pressure rise, along with the resulting sound wave, is smaller.

One design approach to reducing combustion noise is to shape the injection – setting the rate slow at first and then faster – to reduce the amount of fuel entering the cylinder during the ignition delay period. Another is to use indirect-injection (see Chapter 6).

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FUEL ECONOMY
Here again, engine design is more important than fuel properties. However, for a given engine used for a particular duty, fuel economy is related to the heating value of the fuel. Since diesel fuel is sold by volume, fuel economy is customarily expressed as output per unit volume e.g., miles per gallon. Therefore, the relevant units for heating value are heat per gallon (Btu per gallon). Heating value per gallon is directly proportional to density when other fuel properties are unchanged.

ASTM specifications limit how much the heating value of a particular fuel can be increased. Increasing density involves changing the fuel's chemistry – by changing aromatics content – or changing its distillation profile by raising the initial boiling point, the end point, or both. Increasing aromatics is limited by the cetane number requirement (aromatics have lower cetane numbers [see Figure 4-7]); changing the distillation profile is limited by the 90% distillation temperature requirement.

Combustion catalysts may be the most vigorously promoted diesel fuel aftermarket additive (see Chapter 7). However, the Southwest Research Institute, under the auspices of the U.S. Transportation Research Board, ran back-to-back tests of fuels with and without a variety of combustion catalysts. These tests showed that a catalyst usually made "almost no change in either fuel economy or exhaust soot levels."2 While some combustion catalysts can reduce emissions, it is not surprising that they don't have a measurable impact on fuel economy. To be effective in improving fuel economy, a catalyst must cause the engine to burn fuel more completely. But there is not much room for improvement. With unadditized3 fuel, diesel engine combustion efficiency is typically greater than 98%. Ongoing design improvements to reduce emissions are likely to make diesel engines even more efficient.

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HEATING VALUE
The heating value (also referred to as energy content) of diesel fuel is its heat of combustion, the heat released when a known quantity of fuel is burned under specific conditions. In the U.S., the heating value is usually expressed as British thermal units (Btu) per pound or per gallon at 60°F. (International metric [SI] units are kilojoules per kilogram or per cubic meter at 15°C.) For gross heating value, the water produced by the combustion is recondensed to a liquid. For the lower net heating value, the water remains as a gas.
Since engines exhaust water as a gas, the net heating value is the appropriate value for comparing fuels. Heating value is customarily expressed per unit volume, specifically Btu per gallon, because customers buy fuel by volume.

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1 In engine terminology, brake horsepower is the usable power delivered by the engine (see Chapter 3). The smoke limit is the fuel-air ratio at which visible particulate emissions become excessive and are no longer acceptable.

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2 David S. Moulton and Norman R. Sefer, Diesel Fuel Quality and Effects of Fuel Additives, Transportation Research Board, Washington D.C., 1984, p. 23.

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3 Rather than repeatedly use the awkward phrase "addition of an additive," the petroleum industry has coined the word "additize."

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Gotcha, I think.

 

Now that's a post!


That was good reading and helps to explain white smoke, slow starting and poor fuel economy (only when compared to other FTE member claims).
Although the white smoke and sputtering on my truck only occurs when warm and after I recieved the latest reflash, about 4000 miles ago.

 

I promised results from my "test" this weekend. 100hp installed with 16oz per 25 gal--running speed was 85mph, distance of 443 miles--17.75mpg. Mileage for the next tank was virtually the same but included running down a 600 crummins and kickin his tail--actually was 18mpg. Oil change at stealership/deprogram/reprogram with 65hp and unhook EGR--463 miles--23 gallons--20 mpg. all hand calculated. Performance with EGR unhooked is definitely lower, but mpg's are higher. Didn't have Powerservice for the trip home, but would have definitely been better. OH--forgot to include 3rd tank with no powerservice on 100hp was only 15 mpg then went for scheduled service/oil change.