Fuel Economy for AWD reached 24.9?

[1995E]

Right when I topped off at a shell gas station in Silver Spring, MD, it was raining pretty heavy and I guess I was driving more cautious home. There were some red lights and such but I was cruising mostly at 40 - 48 MPH. I managed to get 24.9 MPG on my AWD? Is that possible? Does rain have something to do with my higher fuel economy?

I'm not complaining by the way, I'm just really confused because I'd definitely like to learn how the heck that happened because it has never happened to me like that before. I want that fuel economy number all the time! I usually get 19 MPG going the route I took today and I have never gotten pass 24 MPG before. Anyone got a clue? I have pictures of what my fuel economy reader said.

 

[Blue Raptor]

Probably due to the speed you were traveling. Lower speeds= increased fuel economy. Unless that's the speed you normally drive.

 

[colintrax]

Actually lower speeds don't = better fuel economy. You'll drink gas if you drive 10mph. 50mph is generally considered the most fuel efficient speed. However every vehicle is different, it should be the lowest speed you can go in the tallest gear without lugging the engine to hard. Most of the newer vehicles can get better mpgs at 60 than 50.

Rain will hurt your gas mileage, not by much but it does increase your rolling resistance.

 

[tucker_bmd]

How many miles?

To the OP, was this a full tank? Just curious. I do a lot of highway miles at 70 mph on cruise control and the computer will tell me I average over 30 mpg for one 5 minute interval on the mostly flat to downhill section of my commute. I've posted my mileage in other threads, last "summer" I got 24.2 mpg over 14k miles.

Rain generally hurts mpg, it increases aerodynamic drag. Engines do have a sweet spot for efficiency. My VW Jetta TDI loved 2000 rpm in 5th, about 60 mph, too slow for my taste, but it would get 55+ mpg. Speaking of 55, mph that is, the US's only engineer president was onto something when we got the national speed limit, there was analysis done by smart people proving slower speeds will save gas.

 

[machine4321]

I just did a 600+km drive and got 23.8mpg and it still said I had 60km till empty. I was pretty impressed. Alot of that was at 120 kph. I find the best mpg when right around 85-95kph. I was a mix of 80% hiway 20% city

When I filled up it said 686km to empty. Thats a high for me.

 

[1995E]

To the OP, was this a full tank?

Yes. It was a full tank! That's why I'm so surprised! Plus I had a passenger and some bags in the back. I guess I should travel just 45 MPH from now on through that route. With this being in the rain, I'm just really surprised my fuel economy was so high. Especially since I hit a some puddles here and there pulling the car back like 1 MPH.

 

[peterk9]

Right when I topped off at a shell gas station in Silver Spring, MD, it was raining pretty heavy and I guess I was driving more cautious home. There were some red lights and such but I was cruising mostly at 40 - 48 MPH. I managed to get 24.9 MPG on my AWD? Is that possible? Does rain have something to do with my higher fuel economy?

I'm not complaining by the way, I'm just really confused because I'd definitely like to learn how the heck that happened because it has never happened to me like that before. I want that fuel economy number all the time! I usually get 19 MPG going the route I took today and I have never gotten pass 24 MPG before. Anyone got a clue? I have pictures of what my fuel economy reader said.

Your speed and the moist air would both be a plus in helping boost your mpg.

Peter

 

[1995E]

Your speed and the moist air would both be a plus in helping boost your mpg.

Peter

How would moist air increase efficiency? Wouldn't moist air mean more water content in the air fuel mixture?

 

[peterk9]

How would moist air increase efficiency? Wouldn't moist air mean more water content in the air fuel mixture?

I just did a quick Internet check on this and it seems that I was incorrect with the moist air part. I guess I maybe went too far back in years of driving. It always seemed to me that the engine appeared to work a little better in rainy conditions. In that case, your travelling speed played a major part in your mileage figure. Thank you for your comment. Another lesson learned.

Peter

 

[FIND]

Actually... higher humidity air is less compressible and transfers heat better, so that means higher dynamic compression while not increasing the octane requirement. That's why we use water injection for turbocharged cars, reduces pinging.

 

[2TimingTom]

I've fueled up, driven like 40 miles and then splashed in just a touch over a gallon in my Explorer. And this was driving up into the mountains. 32 mpg.

But over an entire tank, I think 19 is my best.

 

[colintrax]

Actually... higher humidity air is less compressible and transfers heat better, so that means higher dynamic compression while not increasing the octane requirement. That's why we use water injection for turbocharged cars, reduces pinging.

But with the power these cars are putting out, I don't see that helping with the fuel economy (if that's what you're saying? )

 

[182RG]

Actually lower speeds don't = better fuel economy.

Uh.......no

 

[2TimingTom]

Uh.......no

Lower speeds don't ALWAYS equal better fuel economy......

Happy?

 

[FIND]

But with the power these cars are putting out, I don't see that helping with the fuel economy (if that's what you're saying? )

It does help.

 

[182RG]

Lower speeds don't ALWAYS equal better fuel economy......

Happy?

Too funny. Show me one production car that gets the same MPG at 80, as it does at 55. The laws of physics says it doesn't exist....

 

[FIND]

Too funny. Show me one production car that gets the same MPG at 80, as it does at 55. The laws of physics says it doesn't exist....

He was correcting Colin's post. Basically he was pointing out that there is a speed that under which you are not increasing fuel economy, and are actually losing it because of the gearing you use while traveling at that speed. 55 is much more efficient a speed to travel at than 80, but 25 is a darn inefficient speed to travel at.

 

[dragonexplorer12]

The best FC I've recorded even after an oil change is 17.4 MPG. This is a mix of expressways, rural highways and city driving. Air conditioning is always on since I live in a tropical country. I've noticed that I get better fuel economy when cruising at 100-120kph with RPM steady at 2k-2.5k.