We took a road trip this weekend . . .

Pittsburgh to Philadelphia on Saturday, then back to Pittsburgh on Sunday,
all on the PA Turnpike. Travelling east, we got 31 MPG, but traveling west
this decreased to 29 MPG. This really tells how much the wind direction
effects mileage.

Rachel

 

there could be a different explanation. elevation of Pittsburgh is 45 feet and elevation of Philadelphia is 1223 feet.

 

that means they were going downhill on the way back which doesnt explain the lower gas mileage :hehe:

 

No, it just shows that something was different. I doubt there was a constant wind the entire trip there, while you were in Philadelphia and all the way back.

More likely it has to do with speed, temperature, humidity, etc. You can't pin it down on wind from that singel observation. By any chance did you buy gas in Philadelphia? Di you buy anything in Philadelphia that would have made the car heavier? That would throw a wrench in it too.

 

Maybe too much knoshing on those Philly cheesesteak sandwiches.

 

The TL does get great mileage when driven for it. I just took a trip from upstate SC (elev 700 ft) to Daytona Beach (elev 50 ft). I got 31mpg running around 75 on the way down and got 29 on the way back running closer to 80 (average 77). I think elevation may have a little to do with the difference, but speed is likely the main difference. Once after filling up and resetting the TC, i got 35 mpg averaging 65 mph for about 30 miles. (This leg was also part of the trip down, so it may have helped boost that number.)

berlinrl, do you know your average speeds? Were they they same?

 

Does anyone ever calculate by yourself?


I found out my TL's MID isn't that accurate while MPG > 27. MID seems to tell you "better MPG" than you actually have.

For example, if MID tells me the trip has 32 MPG, my own calculation will only show 29~30 MPG.


(I always try to fill up my tank by myself to "the same level"... in past 15 years...)

 

Slight variations in filling the tank will result in variances from the MID. Filling up one time on level ground, and then next time on an incline, might result in the amount of fuel in the tank being at a different level.

Other factors come into play here also. If your actual computed miles per gallon comes out to 29.6-30.4, the MID will show 30. Also, filling up on a hot day will give a different figure than filling up on a cool, damp day.

I have always manually computed miles per gallon figures after each fill-up, but since finding the MID is always, in my case at least, extremely accurate, I just note the MID MPG before holding down the reset button.

 

I'm fully aware of those factors... and still experimenting on these issues... in my computer database, I have all my gas/gallon/price/mileage info since 1990, and always make sure myself to fill up the tank by the similar way and the uniform standard if possible.


So far, my issues/problems are only showing up in those high MPG trips. If I got 30 MPG, the MPG by my compute is usually around 27-28. In my amazing trip with 500+ miles, my MID display 34+, but I got 31~32 MPG after the calculation.


My car is around 20k, and there are 30+ fill-up with MPG > 25~28... 90% of them are showing up the similar result... hopefully this is only happening on my car...

 

I think you have this bass-akwards. I would bet you pink slips that pittsburgh sits at a higher elevation than Philly.

 

Interesting.... but it has to be more than just wind and elevation. How hard you accelerated things like that make a difference... how many times u passed people... etc etc

 

Average speed was higher on the return trip . . . about 72 rather than 69.

Interestingly, the previous week we went to Williamsburg for Thanksgiving and
had similar results.

Pittsburgh to Williamsburg 29 mpg
Williamsburg to Pittsburgh

 

Average speed was higher on the return trip . . . about 72 rather than 69.

Interestingly, the previous week we went to Williamsburg for Thanksgiving and
had similar results.

Pittsburgh to Williamsburg 29 mpg
Williamsburg to Pittsburgh 27 mpg

(We had a lot more traffic on this trip, given that it was a holiday
weekend)

On this return trip to Pittsburgh (Saturday, 11/28) I could feel myself
driving into the wind. Gusts were about 30 mph.

 

Just returned from round trip Ottawa to Destin Florida, 3 day drive, 1500 miles each way, average speed 65mph, and average of 29.6 mpg.

 

Keep in mind it also depends on the gas. Different gas stations put different additives in their gas. My #1 choice is 76. I Use it on my motorcyle and gets good miles. My least choice is Cheveron. The techron is good for cleaning your engine but horsepower is reduced. So if you are testing MPG, be sure to use same type of gas from the same station. Not a lot of people know that.

 

my guess is that you're riding in the Jet stream, and back you were against it Just kidding

 

That might be it, but my guess is it has more to do with the rotation of the earth

 

we liv in a small town and use the tl daily to got 2 miles back and forth each day (ben a yrs, only 3200 miles lol) the ave. mileage is 18mpg???!!! seems ok in comparison wit our suburban...

 

Sounds like wind could be the big difference. I would expect that air drag has the biggest impact on gas mileage on the highway. ( At city speeds mechanical drag - tires, gears etc - is likely a bigger factor.) If you were driving 70 with an average 20 mph wind going the same way, the wind drag would be more like 50 mph. In the return direction the effective speed would be more like 90 mph. With that difference, I would not have been surprised at an even larger difference in your mileage.


Also, rets, for the first 3 or 4K miles, I calculated each tank and compared to the TC. I rarely found it only off by 1 mpg. I did a long average and it was maybe 1/2 a MPG high. I suspect that each car is slightly different.

Lakeman

 

I think you have that backwards. Philly is on the coast and the 'burgh in the hills of Western PA. That would lend some cred to your theory.

 

Thanks for your input. I'll keep paying attention to this issue on my TL.