S15 (ULSD), S500 (LSD) and S5000 diesel fuel

[SkyPup]

Originally Posted by SkyPup

The American Petroleum Institute will be producing three kinds of diesel fuel labels for all diesel fuel pumps in North America, and soon there will only be two:


All Diesel Fuel Pumps must be labeled by June 1, 2006.


ULSD (All On- Road)



LSD (soon to be classified as Off-Road Red Dye added at terminal)



HSD (soon to be phased out completely)

Yup, that's 100% correctt!

[dmccarty]

Would the higher cetane in ULSD provide better mpg?

My station still has the 500ppm diesel fuel stickers on the pump but I assume they have moved to ULSD at this point.

My last fill up the hand calculated mpg was 21.3. This is WAY out of my normal mpg. The driving I do in the summer consistently gets 20.5 maybe 20.6 mpg. And this is the most I ever get in the truck. I'm doing the same old route and speed and the mpg jump to 21.3. The truck computer is usually off by .5 to maybe 1 mpg. This last fill up it was at 21.3. Sometimes the computer gets it right. What has been happening for years is that the computer shows 21.3 and I get 20.5/20.6. And 21.3 on the computer is the most I would see. Now I'm seeing 21.6 on the computer which I have never seen before.

The problem is that next week school starts up for the kids again so my route will change and the mpg historically falls to 19.5 to 19.8 mpg so I won't be comparing the same route on the next fillup.

Could the extra cetane cause this?

Later,
Dan

[SkyPup]

Higher cetane contributes nothning to higher mileage, to get higher mileage you need more BTU's per cubic volume of fuel, cetane does not increase BTU's.

Maybe the previous low mileage fuel you were using had biodiesel in it, that would lower your mileage compared to petrodiesel.

[dmccarty]

Nope, no biodiesel. Its an Exxon/Mobil station.

I almost always buy at this station and at the same pump. Heck, I can't even remember the last time I bought fuel from somewhere else.

Later,
Dan

[HGM]

Originally Posted by SkyPup

Higher cetane contributes nothning to higher mileage, to get higher mileage you need more BTU's per cubic volume of fuel, cetane does not increase BTU's.

Maybe the previous low mileage fuel you were using had biodiesel in it, that would lower your mileage compared to petrodiesel.

Not sure I agree with that...

cetane number

NOUN:

The performance rating of a diesel fuel, corresponding to the percentage of cetane in a cetane-methylnaphthalene mixture with the same ignition performance. A higher cetane number indicates greater fuel efficiency. Also called cetane rating

By increasing the cetane rating of your fuel, you are also increasing the efficiency of the burn.. By doing so, you make for a more complete burn, smoother idle, more power, and better efficiency.. So, I would havy to say, yes it would be the reason you see better fuel economy..IMO..

[SkyPup]

You may be correct about that, I can certainly see that if the cetane level is too low for fuel ignition to occur at the proper fuel injection time, in the crank angle window, that it would inhibit ignition and therefore decrease mileage from the retarded ignition.

Once the cetane level in most modern diesel engines is up to 50 though, any higher cetane level will not be benefical.