Great Experiment. I haven't added anything to my fuel I'm starting to think I've been lucky having no problems. Next cold snap I think I will try doing it here. I have no idea what is in our diesel the pumps just say diesel.
So the verdict on anti-gel, anti-cloud additives is..... ?
Either us an additive or a mix of #1 and #2 diesel when the temps get below 10 degrees if you park your vehicle outside.
The key with the additive is to get it in the fuel before it hits the cloud point. Once it starts to cloud the additive is not very affective at reversing the process. And always carry a bottle of 911 or equivalent. When you see or feel any signs of gelling (fuel press drop/power loss) dump it in there ASAP.
Here i a copy of one of the tests. This diesel sample had the Schaeffer's Winterized Dieseltreat additive added into it.
It shows the cloud point at 10F and the cold filter plug point at -22F. But there is a catch (there always is) .This does not mean the fuel will gell at or below -22F in my 7.3L. Keep in mind that the CFPP (cold filter plug point) determined by the ASTM D6371 test uses a 45 micron filter. IIRC the fuel filters in our 7.3L Powerstroke is 14 microns and some of the newer diesels are 2 microns. So the CFPP will actually be much different.
This is also the problem with some of the marketing on these products. read the back of the bottle and see what some companies claim there product will do. Unfortunately the ASTM D6371 standard is pretty old and IMO can no longer be applied to newer diesel engines. Each company is following the standard test, but unfortunately the standard does not apply to our vehicles.
How much do these tests cost? How long does it take to get results?
As for the CFPP, could you request that they test with a "tighter" filter instead?
According to the above results, the cloud point +10F and the CFPP is -22F. Lets assume, for arguments sake that the CFPP is accurate. (even though I understand why its not) So, we are saying that at -22F, the filter is plugged. The truck won't run. Pretty simple and clear cut.
But, there is a 28deg swing between cloud and CFPP. At what point will the truck technically still run, but not in an acceptable manner? at what point will it run acceptably ("good enough"), but with degraded performance?
Here is another thread that gets into more of the details about winter blend diesel fuel and how it is more region specific. Why those that drive up from the south on a different blend and occasionally encounter problems.