Actually the less dense air cause better gas mileage if you are driving conservatively. You don't need very much horsepower to keep your car going at highway speeds. In fact most cars produce more horsepower than they need to travel at a constant speed in top gear. So by injecting warmer less dense air you reduce the amount of fuel being used and as a consequence you get less power. I think this effect is why people report getting good gas mileage when they drive in high altitudes. A different concept but having the same end result is the cylinder deactivation that is showing up on larger engines. Now if you are going to drive like a bat out of hell you will get worse gas mileage because you will have to press the accelerator harder to achieve the same acceleration you would get with cooler temperatures.

 

Actually according to the National Conference on Weights and Measures, every 15 degrees over the standardized temperature for the pump results in a 1% variation in volume. If you have a 30 degree temperature delta between the coolest and warmest temperatures during a week, that's 2%.

2% in itself isn't much when you're talking $1.00 gas, but at $4.50, if you're a heavy driver it'll add up over the year to potentially equate to a few hundred dollars. You can do the math by figuring out what the average daytime temperature is, on an annual basis, then calculate how that affects your volume over the year.

For someone like me who drives 5000 miles a year, it's no biggie (especially since I live in a region that, at night even during the summer temperatures drop back to mid-50s. For someone that drives 15,000 miles a year, it's potentially big if you live in the southern half of the states.

 

=[.. oh no.. reading that last post got me scared.. i average about 15k miles a year.. even though its only been a year.. and for some odd reason i can only get about 23 mpg on 90% highway.. and i only have 18"s.. i mean yeah it would make a difference..but how do the poeple that get 40mpg on freeway do it? heck. how do people get over 23 on city.. i get crap mileage.. then again there are lots of hills.. but i dont think it would do much to my mpg would it?

SinZz--

 

California emissions will kill gas mileage...

 

There is a specific way to deal with hills. You accelerate when you are going downhill, maintain speed when it is flat and let off the accelerator slightly as you go up hill. Finding the right balance between acceleration and coasting is going to depend on the size of the hills. The highways around Chicago are pretty flat but do have some small rolling hills. When using cruise control my instantaneous mpg will vary from 23-42 mpg. When I use the method described above I get a variation of 32-55 mpg, weighted more to the higher numbers. The problem with cruise control is it will try to regain speed as very quickly and then it will limit your speed on a downhill.

On another note rain really affects your mpg. Today on my way to work it was raining fairly heavily and my average mpg was down ~3 mpg. If you think about it striking all those drops of rain will have a speed impact.

 

Haha, it's not really the rain drops slowing you down, but the road. The rain on the road causes resistance on the tires which makes the engine work harder, so lower MPG.

I average 29MPG usually. Mixed driving I will get 26-27 and with highway driving get 30-33. I don't accelerate slowly either but moreso coast to red lights and off highways, I don't go more then 5 over the speed limit, use cruise anytime I can, etc...

Coasting and cruise control will help you the most with your mileage for sure. Just remember, anytime you do brake you are wasting energy that you built up. By limiting your braking and reading the roads ahead to adjust speeds or let off the gas you not only get much better mileage, but your brake pads will last longer too!

 

So Cal freeways = no coasting and very little cruise control...

 

It seems then your out of luck!

Ohio freeways = no traffic and can cruise control everywhere.


At least you guys don't have winter!

 

You're right the rolling resistance of the wet roads will have the largest impact on mpg.

 

LOL, that method doesn't work when going through mountain ranges. You guys must have really tiny hills if you can coast over them.

 

Highway In Miami Im getting 28 to 31 on the Hwy on the instant meter and on the average MPG meter or total Mpg Im averaging like 19-21 combined driving pretty bad I KNOW but I am hoping for MORE once broken in im only at 600miles...

 

I'm in Dallas/Fort Worth area, first tank on this 09 auto xb, 50/50 city/highway, with constant A/C on, max 45 MPH city, max 65 MPH highway, I'm getting exactly 27 MPG per the computer. The car got 314 miles on it right now.
I traded in my 02 manual Mini Cooper S for the xb because I need a bigger car for my family, but i'm getting slightly better MPG on the xb (26 MPG for the Mini) due to my new Green driving style. Consider that the xb is like a wind blocker and 400 lbs heavier than the mini, I'm very happy w/ the mileage I got so far. In my old Cooper S, highway speed is rarely below 80 MPH, city driving is very aggressive w/ lots of down shift and pedal to the metal.
So, bottom line is how you drive that determine your MPG. Drive like a maniac and you will never get good mileage, drive like an old man and you will surpass what the EPA rating for your car.
And why this new revelation and green consciousness you all ask? Money talk, and at $4/gallon and still going up, it changed this old dog.

 

Hmmm... my mpg average is 20.3 so far and I only have about 80 miles on my xB. It's still going up!

 

anyone from So Cal know how to up the mileage of the cars? i really dont think my 18"s can affect it THAT much.. i dont even have any engine mods minus the exhaust.. =[[[ help please

SinZz--