I'm revisiting this due to some MAJOR fluctuations I have seen recently. For my fill up two weeks ago, I got 31.5 MPG on the tank. I just filled up this morning and averaged 36.2 MPG for the most recent tank. Air temparatures were pretty much all over the place for the duration of both tanks (form the 30's up to the 70's) and driving conditions other than that pretty much identical too. Why would the mileage vary almost a full 5mpg over a two week time period? That is a substantial difference.

 

Sounds like they got rid of winter blend gasoline and started spring blend.

What that means, depends on where you live. It's a big deal up north and not-so big in the south.

 

I have noted with mine, an 06 FEH, that you can track the mileage down & up with ambient temperatures. It does not follow a step change s would occur with a shift from summer to winter blend and back. Rather it is roughly proportional to the average temperature deviation from the 80s.

I attribute this to the amount of heat up required from cold to operating temps on the engine. That takes energy which means gas. So the longer the heat up the poorer the mileage. You might look back and see if the number of starts from cold make a difference. For example if you take a trip and start and warmup just once for a full tank is the mileage better than a tank with around town and many starts from cold?

Much of my driving in the winter is short hops to work in the morning and back in the evening. Hence the mileages I have mentioned.

In essence I see 29-31 in the summer and as low as 21 in the winter and it just follows the ups and downs of outside temps in the midatlantic.

 

Sascol, do you typically fill up at the same gas station (near home or work perhaps). If not and this uptick in FE is not realized in your next tank, I expect you found a station that had 100% gas and not E10. I was recently in Greenville, SC and found a station advertising 100% gas. I had a half tank of E10 but I topped off with the 100% gas anyway (so I effectively had a tank of E5). We finished the tank with about 36MPG with ~70%hwy miles. With E10 we're usually right at 32-33MPG with a 50/50split.

I really miss 100% gas down here on the coast.

 

I don't think the E-10 is the culprit. Alcohol has roughly 60% of the energy of Gasoline. To figure the equivalency I just use 50%. So E-10 would have 95 % of the energy content of straight gas.

So, as I see it, the kind of drop you saw is not just the E-10 issue. Some winter blends also include oxygenators that might just reduce the milage some. But in the end I think the answer lies somewhere else.

 

Here's the issue I have with the E10 vs straight gas energy content argument:

While the energy content of Ethanol may be 60% of gasoline and an E10 tank has 95% of the energy, it doesn't mean that FEHs (or other vehicles originally designed/programmed for 100% gasoline) are going to be able burn it at the same efficiency level.

I expect that Ford (and other manufacturers) realized that E10 was going to be the norm going forward and took steps in their design/programming to adjust. I think that this is one reason why the 2009 FEH reportedly handles E10 better.

Unless Ford (and others) are willing to make alternate programming available, I don't think older (than 2009?) vehicles will ever see that 95% equivalency E10 may have.

I do need to amend my previous post slightly as I just finished the E5 tank. My FE average over the past 4.5 E10 tanks (prior to this E5 tank) was 31.55MPG. This E5 tank was 35.39MPG (I was expecting ~36 from what I was seeing on the NAVI and I wasn't off by much). In any case, I was able to take a 70% highway tank and get a 12% increase over my normal FE. Argue all you want about temps, driving styles, etc. but these are the numbers I'm seeing and it's convinced me and my wallet that E10 is not good and is responsible for more than 10% FE loss in my FEH.

As I've said before, E10 causes me to burn more straight gasoline on top of the Ethanol that I burn. By my understanding, any vehicle with a FE loss of over 10% with E10 is better off without it unless it's cheaper or you feel it reduces emissions. When I bought the straight gas for the recent E5 tank, it was $1.799 and cheaper than the E10 I bought two days earlier at $1.859. As for emissions, since the FEH is already SULEV rated with 100% gasoline, I'd say the difference is negligible.

 

You and I agree on this issue but I really don't know the real effects of E10 on my '09 FEH because I can't get straight gas to compare. I know that if I drive just a little more aggressively my mileage will drop a great deal. I think the '08 - '05 FEH 2.3L is fine on straight gas but take away any energy with E10 makes it grossly under powered for the heavy body. Even on straight gas you can see the effects of the A/C compressor on any small engine vehicle. The bigger and more horsepower engines have less of a MPG hit with the A/C compressor running and I would say the same with E10.

As I read through this thread today my thoughts were that E10 may have been the start of Sascol problem. When you lose that energy everything else is compounded. The defroster, hills, wind or anything that takes more energy will compound your MPG. Also, the fuel maps for air/fuel ratios must adjust to E10 which is spelled out in the PCM/ED manual. What about the cold dropping the PSI in the tires?

Anytime you see a sudden drop in MPG there is a reason. Just changing the oil I found the oil in '09 FEH cannot be fully drained on front wheel ramps. This was the first time I've ever experienced an oil draining problem with my ramps. My mileage has improved by draining 1/2 quart but I need to drain it a full quart I think. This had nothing to do with me overfilling the oil, the old oil cannot be fully drained on an incline.

GaryG

 

Not trying to defend cutting gasoline with alcohol. I don't like it either. But alcohol's characteristics are straightforward: higher octane (108 or so) and half the energy. So long as the fuel injection system proportions the fuel correctly the engine will run fine on it.

There is a reason the Indy cars run on alcohol based fuels: higher octane. They can get more performance out of their fuel and far higher RPMs. They also change the compression ratio so that they can take advantage of that.

In my 92 Suburban (375k & has to go until son #3 finishes college) I don't notice the difference in mileage with E-5 or E-10 vs straight gas. I've been tracking mileage for its life as I have on every car.

What I have noticed in my FEH is a very clear tracking of mileage down with temps and up with temps. I've never seen an engine so sensitive to ambient temps. Try recording the daily average temp every day for several tanks and see what that produces.

I feel that blaming poorer mileage on something without tracking the inputs doesn't get you the info you need.

As an engineering principle the surface to volume ratio of a heat engine makes a difference. The losses to ambient of heat (read energy that is lost & therefore gasoline burned) will be higher. Note that these engines are physically smaller than the classic V-8 we were used to for so many years and aluminum blocks conduct heat away from the engine far better than cast Iron.

This sizing difference will make a difference in such things as we're talking about here. I am frankly surprised at just how much difference it appears to make with mine. But there you are.

I do run straight gas when available, but I also buy the least expensive gas I can find and have never noticed much difference between brands over the years. '71 Plymouth Duster, 225 Slant six: 161k; a '81 diesel wagon; '92 Suburban 350 V-8 375k; '01 Mustang DOHC V-8 251k.

Just never seemed to make much difference until the FEH came along and its the smallest engine vehicle I've ever had. The relation with outside temps in my observation is quite clear.

I use a spreadsheet and record odometer, date, cost, & gallons (& then have it calculate the MPG). Try adding two columns, one for Gas, E-5, or E-10 and one for temps and record the daily average temp from the Weather Channel for the area you're driving in. See what turns up.

 

There is another issue to consider.

In non-hybrid engines there are two ways to produce more power: increased RPMs and increased fuel while the transmission holds engine RPM nearly constant. In the latter case the engine produces more power by increasing the peak cylinder pressure.

The hybrid setup cannot do this. It can only increase engine power output by raising RPMs. This happens because of the interaction of the engine with the synchronous machines in the transaxle. The Synchronous machines can only raise power by raising RPMs.

If you watch the engine RPM while on speed control you'll see this clearly. Increased RPM means that fuel consumption will go up since there is increased internal friction from that higher RPM.

Not sure just how this would interact with the specific issue raised here but it is a difference from the engines and transmissions most are used to.

A method for saving fuel while cruising on speed control is to disengage it when climbing a moderate to steep hill and allow RPM to rise only, say, 500 or so. This seems to translate to better mileage with only a loss of 5 mph.

 

Right. Cruise control actually works in a completely counterproductive way when trying to maximize fuel efficiency; it works the engine even harder when going up difficult hills, and it slows the car down during a descent, which limits motor-less cruising.

I do find in my Prius, which uses the same hybrid system as the Escape, that temperature and driving time seem to have the largest impacts on fuel economy. No doubt gas blends contribute, but nothing will slaughter your fuel economy more than a few 5-minute trips on a 30-degree day.