Up until this past weekend I did not believe that there was a difference between the diesel from different companies. This past weekend we to a trip to Silver Lake in Michigan. Silver Lake is a off roading State Park. I left Chicago with the camper and a half tank of diesel purchased from Citgo. The MPG by the time I filled up in Indiana was 11.4 MPG which is normal when I go from the unloaded truck to the truck with the camper. I filled up at Pilot we kept a steady speed of about 65 MPH. The MPGs kept going down until we got to Silver Lake where it was at 10.9 MPG. On our way back I filled up at BP near camp. Gas mileage started to go back up even though we were traveling at 70+ MPH. By the time we got home the MPGs were back up to 11.4 MPG. Since I always use a cetane booster I figured that the basic diesel fuel did not make a difference. I guess I was wrong. the truck seems to run much better on Citgo and BP. It is quieter and there is more power when I step on the gas. Has anybody else experienced this or did I miss something.

How many miles did you travel all together. Does your truck have a diesel particulate filter that has to regenerate? With a truck camper that much difference in mileage isn't that rare. I drive a 2011 Chevy D/A and also have a large TC. Things can very pretty quickly with any change in the wind or terrain. JMHO

I think it makes a difference, but also wind or slight elevation changes can as well.

I don't think a delta of .5 mpg from tank to tank means anything.

I have heard talk of the difference in Winter blend and Summer blend.

I would not put much in the differences in single tanks. Mileage can vary quite a bit on wind, elevation change, speed, traffic, type of terrain, temperature, etc. You would need to run multiple tanks of each fuel over time to know for sure.But this are also differences in cetane ratings of various brands. Some, including Pilot, Flying J, Valero, and others have cetane ratings at the minimum of 40. Others have cetane ratings in the mid to upper 40s according to info posted here in the past.

Diesel Fuel Quality and MPG | Good Sam Community

NHIrish
Explorer
May 09, 2014
ah64id wrote:
jimh425 wrote:
ah64id wrote:
Cetane booster actually lowers the useable BTU's and thus economy. This has been proven on the dyno, and chemically.

References? It it is somewhat common knowledge that additives are a good thing especially with respect to adding lubricity.

Lubricity additives are good, and Cetane additives can be good as well when used at the appropriate time... but 99% of the time, or more, they don't do what people think they do.

My motor will actually sound horrible in the right conditions with Cetane boost, same conditions without it and it sounds normal. They are designed to run on the level of Cetane at the pump.

Cetane is really only good for helping the truck start, and improving the quality of combustion at low temp and low load.

I run Amsoil Diesel Concentrate, it does all the things I want without a Cetane increase.

As you can see here anytime Cetane is increased the BTU's decrease.

You are right about the fine print, but there is more to it...

http://farmweeknow.com/blogs-benefits-high-cetane-diesel-fuel-3681
wintersun
Explorer II
May 09, 2014
When I travel south I have the wind at my back. Returning and heading north I am driving into the wind. Difference of about 20% in MPG. If the wind is up over 15 MPH the difference can be as much as 30%. A truck with a cabover camper has the aerodynamics and drag coefficient of a brick.
AH64ID
Explorer
May 08, 2014
jimh425 wrote:
ah64id wrote:
Cetane booster actually lowers the useable BTU's and thus economy. This has been proven on the dyno, and chemically.

References? It it is somewhat common knowledge that additives are a good thing especially with respect to adding lubricity.

Lubricity additives are good, and Cetane additives can be good as well when used at the appropriate time... but 99% of the time, or more, they don't do what people think they do.

My motor will actually sound horrible in the right conditions with Cetane boost, same conditions without it and it sounds normal. They are designed to run on the level of Cetane at the pump.

Cetane is really only good for helping the truck start, and improving the quality of combustion at low temp and low load.

I run Amsoil Diesel Concentrate, it does all the things I want without a Cetane increase.

As you can see here anytime Cetane is increased the BTU's decrease.
jimh406
Explorer III
May 08, 2014
ah64id wrote:
Cetane booster actually lowers the useable BTU's and thus economy. This has been proven on the dyno, and chemically.

References? It it is somewhat common knowledge that additives are a good thing especially with respect to adding lubricity.
generaljean
Explorer
May 08, 2014
We notice a difference in diesel mileage traveling from Michigan to Florida in december and then again Florida back to Michigan in April. We figure most of it is due to temperature change and the diesel engine running better in warmer climate. Might be a factor for you?
Raften
Explorer
May 08, 2014
Since biocides was mentioned, if your truck sits a lot and if you use a biodiesel blend, put some biocide in there. It might just save you a problem with filter clog.
trail-explorer
Explorer
May 08, 2014
gpascazio wrote:
.... Gas mileage started to go back up.

you put gas in it?
mlts22
Explorer
May 08, 2014
I can see two diesel additives: An anti-gel to use in the winter so the paraffin stays liquid. Then, a biocide, especially with biodiesel, to keep the bugs at bay. I read about cetane boosters and other stuff, but I've not really seen anything it helps with, but I could be wrong, but like posted above, it might be useful for long periods of idle time.
AH64ID
Explorer
May 08, 2014
In 85K miles I have only ever had 1 tank if fuel that was subpar, 14 mpg empty and the next tank was 17. Both the same day on the interstate with similar weather. I'd never hit 14 empty prior, and haven't since.

Cetane booster actually lowers the useable BTU's and thus economy. This has been proven on the dyno, and chemically.

About the only time Cetane booster is good is when the tank will primarily be used in cold weather at low load. I use it for elk hunting and the like, where I won't get above 20 for a few hundred miles and many hours. Engines are designed, timed, around the cetane from the pump and that's perfect nearly all of the time.

I won't buy additives with cetane boost for this reason.
drc5900
Explorer
May 08, 2014
In concurrence with the above posters for possible causes.

For me, a 0.5 MPG fluctuation isn't something I would get excited about.

When I travel many miles, I keep track on paper with actual numbers, and don't go by display in cab. If over many 1000's miles a negative difference would occur for a specific fuel brand, I would avoid that.

Did on all fill-ups a perfect top-off happen?