Yes and no. The cetane rating of the #2 diesel you put into your vehicle has a direct effect on mpg. The higher the cetane rating, the cleaner the burn. Specifically, the cetane Number (abbreviated CN) refers to the combustion quality of diesel fuel. It represents the time delay between the start of injection process and the the point where the fuel ignites. The cleaner the burn, the higher the mpg.

I try to avoid all "discount" stations, truck stops, and min-marts in general. It's an almost dead certainty that you'll be pumping 40 cetane fuel. The below list is a little dated, but here's what I carry on my sun-visor:
BP; (Amoco branded), 51
BP; (Powerblend 47, otherwise 40-42)
Chevron; 49, or 51 with Techron D
ConocoPhillips; through the 76 stations (California)
Countrymark fuels; Diesel-R, 47-53
Exxon/Mobil; 43-46
Flying J: 40
HESS; 40-42, can be up to 45
Holiday; 40-43
Husky; generally 40, but can vary by location (41-45)
Love's: 40
PetroCanada; 47-51
Pilot: 40
Sheetz: 40
Shell; 46
Sinclair; 46
Sunoco; usually 50, Gold 45
Valero: 40
Wawa; 40

The reason there's some bold print, is that at those stations you have to pay attention to what it says on the pump to see if you're getting their regular diesel or their better diesel. Unfortunately the only one with a reasonable presence around here is Shell, so I put that straight in the tank untreated. But when faced with pumping 45 cetane or less, I add 12oz of Power Service to a full tank. It raises the cetane number of what you just pumped, hence promoting a cleaner burn.


//greg//

 

^^^ Interesting numbers! I have never actually paid enough attention to realize there was a difference in octane for diesel fuel as well. The two closest gas stations in my area with diesel are Chevron and Conoco/Phillips/76 so I always fill the wife's CD at either of those places.

 

First the pump labels, regulations, etc for B5 and above only regulate the quantity of Bio content to D-2. It is the lubricity of Bio that is the issue. Making the engine oil work harder degrades it quicker resulting in the requirement of more frequent changes.

When last at our dealer a PCNA rep was there asking if any diesel owners were having fuel issues this winter. Our dealer brought me into the conversation where I expressed no problems thus far. The rep recommended using a product like what the Power Service folks make prior to going out in cold temps. The Power Service folks recommend using it below +30F. PCNA rep also recommended using the Power Service product '911' if out in the cold and the engine will not start. These products can be found in most auto parts stores. Will be using this next week when we go off road in the back country. Also taking '911' just in case.

As to 'name' brand vs generic, I use 'name' brands only due to issues we have had using generic gasoline in our 911s.
ie. used Costco gas once, the 911 was not a happy camper!
If you look at Gregg's above post, the cetane ratings are different for each brand.

 

Even though I don't have a Diesel, I found this thread very informative. Learned a lot!
+1 rep points if I hadn't already done so!

 

I knew about it, but ever gas station I've stopped at or driven through to check has been 40 or not marked. Even the stations that Greg lists as supposedly having the higher values.

This is interesting information. I've asked two different dealers about Porsche's stance on using these additives and have been met with a blank stare and no return phone call.

Sheetz is what I put in my CD as they are the cheapest by far around me. I haven't had any issues and get good mileage out of it, but I suppose the first fuel filter service will be the real indicator. The 996 usually gets it's fuel there too, but that's more convience than anything else. Exxon and BP are other go to options.

The only fuel issues I've ever had were from Shell, but I avoid the real no name shops unless there is absolutely no choice.

 

Just a short note. The cetane no. in California is mandated by the state. It has a minimum of 53.
http://www.arb.ca.gov/enf/fuels/dieselspecs.pdf

 

This is good information, does California also have standards for the quality of Bio fuels ?

 

That's about the only good news I've heard come out of California for years. CN53 puts California diesel fuel on a par with mid-grade diesel in Europe. You pull into service stations over there and you often have a choice of three different grades of diesel. In approximate groupings, it's: Regular (CN40-46), Mid-grade (CN47-53), Premium (CN54-60). One chain (Aral) even offers Super Diesel (CN63). The considerably higher mpg claims of many Euro-diesels are generated as a result of using Premium fuel.

Unfortunately, the American FTC does not mandate the posting of cetane numbers at/on the pump. That's typically done at ground level. That is to say, some chains give their higher grade diesel a different branding. Hence the list I posted. With it in hand, you can in some instances identify the approximate cetane level you're pumping; by trade name and branding/labeling differences on the pump itself.

The higher cetane = better mpg is one of the ways diesel fuel differs from gasoline. Higher octane does not necessarily equate to higher mpg. That's why I hope the takeaway here is that price per gallon should not be the primary reason for deciding where to fill up. In the case of diesel fuel, the bigger consideration is cost per mile.

//greg//

 

Good news for me since I don't have to try and figure out what I am getting... haha I was filling up our other car the other day and thought of this thread so I stared to check out the diesel pump and could not find any information on it related to octane!

 

You're still confusing octane and cetane. Other than being fuel stability indicators, they're not the same thing. Since I've apparently not explained it clearly enough, see http://auto.howstuffworks.com/fuel-e...question90.htm and http://alternativefuels.about.com/od...t/a/cetane.htm

//greg//

 

You've explained it fine, I just made an error typing "octane" instead of "cetane" above. When I was at the local Chevron station, I was looking a rating on the diesel pump, however, there were not any. Next time I'll fill up at 76 and see if they list it. I wonder though, if since the minimum in CA is 53, if maybe the stations in CA don't both - or are not required - to disclose the rating.

 

Took the diesel off road into the mountains on fresh snow covered roads. Prior to leaving used a can of Sea-Foam additive the dealer sold me. Other than a longer wait for the glow plugs to heat up, we had no issues starting or running. Temps got down to minus 5 degrees F

 

That explains mileage variations on a recent 2000 mile round trip toeing my racecar from Atlanta to Austin and back. Filled up at a chevron and got 17, truck stops were 15 and the original tank from my home Racetrack was 16

 

Learned lots about diesel even though I don't have one, but considering it.