Fuel brand vs MPG

I've had my new 2010 Golf TDI for one month now. I just filled it for the 3rd time last night. I currently have approximately 1200 miles on the odometer.

The first two fill-ups were using the Delta Sonic station (Webster, NY). I decided to use that station before I even received delivery of the car because it was the only station that advertised "Premium Diesel". I averaged 37 MPG on those tanks.

Last night, because I was getting low on fuel (550 miles on the trip odometer), I ended up filling at a different station (the Gulf station in Fairport, NY). It was an extra 10 cents/gallon vs. the Delta Sonic price, but I didn't want to push my luck driving to the Delta Sonic station, so I accepted the higher price.

It became obvious to me almost immediately, by looking at the MFD, that I'm getting approx. 3 MPG better mileage on the Gulf fuel. At first I was thinking, "Well, the car is breaking in, so that might explain the better mileage." But then I discounted it because the MPG improvement came immediately with the new tank of Gulf fuel, rather than building gradually over hundreds or thousands of miles.

Is this a common occurance? Have others experienced significant MPG swings depending on the brand of fuel purchased?

And if my math is correct, the MPG improvement more than makes up for the higher price per gallon.

Don't count on the engine trip computer to judge your mileage.
Not to mention that your driving habits vary from day to day (and hour to hour) so short term readings from the MTB are meaningless.

The most accurate way to do it is the old fashioned way: divide your odometer reading by the volume of fuel you put into the tank at the next fillup.
MAke sure your driving patterns are consistent.
Make sure you are consistent with the top-up level.
Even then you may see variation fillup to fillup. If you check on your fuelly website you will see that many TDI owners have varying mileages. As much as 25% difference.

Anyway, your car is too new to judge fuel milage at this point.

You will find that there is a quality difference in the fuel that you buy from company to company, but in the end most will yield similar mileage. If you use biodiesel expect a slight drop in mileage versus petroleum diesel.

That should not stop you. Biodiesel is the environmentally friendly way to drive.

Henryp, I agree with everything you say. But I drive the same route to work everyday, in the same traffic. If anything, I've been driving the car harder since it crossed the 1000-mile break-in boundary. But instead of a mileage decrease, it seems to be up. And that increase was noticed on the MFD immediately after filling up with the Gulf fuel.

So I share your skepticism, but am curious about the timing. I will post more details in a week or so, after my next refueling.

Oh, and I don't have access to biodiesel here in the Rochester, NY area.

More likely the season change. New fuel deliveries will probably not be hard-core winter mix fuel, hence will give better mileage no matter the brand. Also, the weather might be moving closer to that sweet spot for mileage) My last Citgo fill up beat my previous Delta Sonic which beat my previous Sunoco (though I seem to always get weaker mileage with WNY Sunoco).

While I would tend to believe it is more likely sampling variations and error than much real change in mileage, there can be some change, but I would expect it to be less.

Keep checking and look at both the on board computer and your manual fill up computations.

My computer values are VERY close to tank fill values, within 0.2-0.3 mpg over a tank.

Yes, some diesels will have more energy/gallon than others. Depends on the type of crude the diesel is distilled from. Some crudes are paraffinic, some naththenic and others have more aromatics in them (but these aromatics now are likely chopped into naphthenics or paraffinics by the ULSD processes).

Some have posted that the BP diesel is pretty good. I use strictly Exxon or Mobil diesel because I get a 10% retired employee discount. So, the diesel by other brands would have to be pretty good for me to use them.

Steve


Based on what you've written, I would stick with the Gulf fuel for a while to see if you can duplicate the increase over several tanks. Then go back to the other fuel to see if there is a retreat.


Tim

In searching Fuelly for similar vehicles to mine (2010 model year, 10 or less fill ups, low mileage or new vehicles,etc.), I've found that I have one of the lowest MPG ratings on there for a 2010 TDI

I'm 4 tanks in, and I've purposely only filled up at Shell stations to keep it as consistent as possible. I'm going to switch it up to another brand for the next couple of tanks and see if I notice any difference, as my daily commute doesn't change much, but I agree with what was said above ^^^; I think it's too early to begin judging fuel mileage.

Time will tell.

Keep a log by date, by brand of fuel and location filled up at, and you will undoubtedly see trends. I've bought fuel in Utah and Wyoming that was a bit smokey under hard acceleration, yet was stirling under Interstate, Cruise Control type mileage. It also stunk like the dickens when fueling up, if you got some on your hands. But it easily gave me 56 mpg in my B4 passat, while in the area, locally.
I used to stock up on Summer fuel here in CA in the end of September, and buy 100 gallons, and use it clear through February, with Power Service White, if I went to the cold weather and snow of the Mountains. Huge difference in MPG between it and winter fuel, even with longer warm ups. It just flat out had more BTU's per gallon.