I purchased my 2015 3.5 in July. 4000 miles on it. Temps in Phx AZ were between 90-110. MPG was consistently 20-21. Now that the temps are colder 40-70, I have noticed a drop in MPG's...17-19. I did a search on this in this forum and read explanations about winter gas etc. I'm not sure that Phoenix has winter gas..no need for it. However I wonder if the oil companies just make it and distribute it everywhere. I need to do some research on that. Something else I've noticed is the louvers in front of the grille stay closed longer during this colder weather I guess for faster warmup (which I really don't need, it's not below 30 deg here)...is this the reason for the drop in mileage...wind resistance? I thought about unplugging them figuring they would prob remain open, but it would surely throw a code and I don't need that. Back to the gas explanation. My wife drives a 2007 4.6 Mustang GT. She uses nothing but Shell Regular in it. She gets 19 MPG all day. If she uses any other brand of gas...mileage drops. She's proven that to me several times. (Hate it when she's right) So I have filled my tank with Shell and will see what the results are. As I stated in the title...this is my observation. Input will be appreciated. Thanks.

 

I get the confusion/frustration. My mileage has dropped considerably since October-ish when the winter gas started hitting the pumps around here. I use the same fuel at the same station all the time. I use Shell regular. There were a few times when I ran 93 because I was running a 93 tune on the truck, but for life perseverance I went back to the normal tune and 87 Shell gasoline.

Now, with that said, my wife drives a 2014 Acura MDX and I haven't seen any drop whatsoever in her car. I'm the one that puts gas in the vehicles and tracks all the mileage. I filled up her vehicle yesterday and got 28.4. It's higher than usual, but she consistently runs between 25-28 depending on town/highway driving ratios. I don't get how some vehicles are more susceptible to the winter gas than others.

I never pay attention to the louvers in the front, but I thought they only closed on the highway for better aerodynamics/efficiency. I guess I'm wrong about that.

 

I believe another factor is that air is more dense when it's colder out thereby making it harder to plow through at highway speeds. That combined with winter gas, longer time to warm up, etc probably all impact decreased fuel mileage in the winter. My 5.3 Silverado dropped a couple mpgs at what seemed like 40 degrees and below. My 3.5EB does the same.

 

I wonder if the mileage drop in cool weather could be more pronounced on a turbo engine. Denser air possibly leads to denser (more) fuel being added by the computer. Turbo engines use more air than a NA engine, so the effect is more apparent. I have no idea if that's possible. Just hypothesizing.

 

I used to be a mechanic in the 60-80's. Carbed cars loved to run the best in damp cold weather. Hence why racers used to run their fuel lines into coffee cans and pack them with ice before a run. It's very weird that my truck gets better mileage on very hot, dry days. Go figure.

 

don't forget winter fuels vs summer fuels

 

About the Shell thing, they don't use ethanol. That's why in the winter I only go to shell to make up for winter gas even though it's out of the way for me.

 

Are you talking about premium? Because shell uses ethanol in regular and midgrade here in Manitoba and I'm pretty sure its standard accross canada. They do have the best additives though.

 

I believe this is a Canadian Shell Premium fuel thing. Ethanol-free fuel is so rare here in the states that there is a secret treasure map with all the ethanol-free stations plotted. There is not an abundance of them. Thank Iowa.

 

The only reason any mfg'r is using active grill shutters is for aero, ie: better fuel economy. Quicker warm ups is a nice fringe benefit for us Northerners. When they're closed, less aero drag through the front of the vehicle. These have a pretty significant impact to the overall rating that goes on the window sticker.


Ambient temp also has a big impact to fuel economy. The colder it is, the worse the fuel economy. The hotter it is, the better the economy. Performance is basically the opposite, especially with turbo motors that generate more heat.....the colder the air, the better (to a point, of course..) the performance. Ever hear street racers comment, you always wanna run the turbo guys on hot, muggy conditions, where power will be down a bit. Cold, dry air, watch out!


Winter blend fuels would be the least impact to mpg's, compared to the 2 reasons above.