winter fuel and additives
 

I use Stanadyne Performance Formula in my girlfriends diesel Liberty and she usually gets around 24 to 27 mpg driving around town this last summer. The last two tanks got 30mpg and 32 mpg. I fill to the top of the tank and hand calculate the mpg every week. Does winter fuel ( we have a winter blend here in Arizona ) respond better to additives than summer fuel ?

Not in my experience, I usually lose a solid 3-5 MPG no matter what.

Around here winter fuel means 50/50 mix of 1 and 2. And a loss of fuel mileage and smoke out the tailpipe.

I see a 2-3 mpg loss with winter blend.

I consistently run Power Service white bottle/red cap year round at 1 oz/3 gallons.

Interestingly, the fuel suppliers here won't discuss "winter blends".

A #1/#2 mix is rare in the lower 48 anymore since anti gel additives at the terminal are cheaper, easier and more effective.
Additive winterized straight #2 fuel shouldn't reduce mileage at all but what does reduce it is colder engines and slower driving conditions.

I would doubt that you have a winter blend anywhere in Maricopa County, except maybe at truck stops.
Mileage change is an anomoly. The better mileage had to be from hiway driving or something. Maybe she's hypermiling now!
I usually see a 1-2mpg decrease in winter (where there's actually a winter). Not sure if it's attributable to the cold wether/cold engine or anti gel additives, but in the last 10 years I've never seen more than 1-2mpg difference betwen fill ups in any diesel I've had unless it was towing vs empty driving. Even city driving vs 100% hiway driving, within a couple mpgs.

I have noticed winter blend is marked on the pumps in Idaho and Montana as "WINTERIZED".

Here in WA though, it isn't, leading me to see infidels statement as making sense about colder temps and slower speeds...

The Exxon stations in Montana have a sign on top of the diesel pumps that say the winterized fuel has Power Service in it.
Friend of mine who drives a fuel tanker says the Power service anti gel they use is extremely concentrated, half a gallon treats a 10,000 gallon tanker.

Sign at Frenchman Valley Co-op/Cenex: 50/50 blend
sign at (one of the) Ag Valley Co-op stations: 30% blend

The local Sinclair doesn't blend, and my truck gelled on it my first winter out here. At somewhere south of 20 below.

Hmmm...1/2 to 10K isn't very concentrated. In fact that seems rather diluted. Most treat ratio I see are 1:300 or 1:500 at most for a good winter additive. I wonder if PS sells Exxon a specially formulated anti-gel package...as in mostly pure anti-gel and little to nothing else with it.

I found I was actually putting a little too much additive in my fill ups.

I called the PowerService rep and he says the dilution ratio for increased lubrication is very concentrated and using more than suggested is just throwing money out the tailpipe.

I go with 1 ounce to 3 gallons of fuel. Doesn't seem like much but it gives me peace of mind that I am doing right by my VP44...

It's anti-gel only. They probably have the anti-gel concentration set up as an easy measure for the standard 10,000 gallon tanker rather than having to measure ounces.

With the standard auto parts store white bottle Power Service one gallon only treats 250 - 300 gallons of fuel.
Guy that brings my fuel treats it for me starting in Oct when he delivers.
Says he's supposed to put in four ounces per 500 gallon tank but he just pours it till it glugs twice from a container that looks like it's been around for a couple of generations. Must work, my tanks have never gelled down to -35°F.