Low MPG on windy days?

[adventureboss]

I’m in the Phoenix area and my last few fill ups have been relatively bad on MPG. I don’t know if there’s something wrong with my TJ (06, 4.0, 6 speed, bone stock) or if it’s just the weather.

At 85 mph on the interstate I used to get 14-15 mpg. Last couple fill ups when I’ve driven out of state I’m getting 12-13. That’s AC maxed out and 100+ degrees outside. I can hear the fan clutch roaring when I downshift. It’s also been very windy lately and I’m wondering if that’s more so the reason for my poor fuel economy.

I also recently switched to 5w-40 oil and put 75w-140 in the rear which I’m starting to think was a mistake. Would the combination of heavier oil+heat+wind cause my poor fuel economy or do I have another issue lurking somewhere? Is anyone else experiencing similar with this crazy weather?

 

[Zorba]

Wind can DEFINITELY affect MPG - ask any trucker. If you're bucking a headwind - esp. in a non aerodynamic vehicle like a TJ, it happens...

 

[adventureboss]

Wind can DEFINITELY affect MPG - ask any trucker. If you're bucking a headwind - esp. in a non aerodynamic vehicle like a TJ, it happens...

Headwinds yes I understand, but it seems driving on the open parts of our highways lately the wind is coming from all different directions. I can feel it shaking the Jeep and so can my passengers. So I guess I’ll just chalk my mpg loss up to the weather?

 

[TJ Jim]

My jk when I drove it to the west coast went from 21mpg to 15mpg. The tranny shifted from high gear which I think was eight, to third gear during the headwinds coming out of the west. So yeah headwinds hurt. Went back to 21mpg going back to Tennessee with a tailwind. Still driving the 85mph speeds y’all have out there. Seems the tailwinds should have got me 42mpg coming back!

 

[NskLJ]

My jk when I drove it to the west coast went from 21mpg to 15mpg. The tranny shifted from high gear which I think was eight, to third gear during the headwinds coming out of the west. So yeah headwinds hurt. Went back to 21mpg going back to Tennessee with a tailwind. Still driving the 85mph speeds y’all have out there. Seems the tailwinds should have got me 42mpg coming back!

You must not of used the road camber and torque band correctly

 

[TJ Jim]

Tried coasting to achieve it but headwinds stopped that

 

[macleanflood]

Takes a second to check live ODB data. I'd check my O2 voltages and fuel trims. That usually tells my brain to shut up when I can see it's all normal.

-Mac

 

[adventureboss]

My jk when I drove it to the west coast went from 21mpg to 15mpg. The tranny shifted from high gear which I think was eight, to third gear during the headwinds coming out of the west. So yeah headwinds hurt. Went back to 21mpg going back to Tennessee with a tailwind. Still driving the 85mph speeds y’all have out there. Seems the tailwinds should have got me 42mpg coming back!

Okay that makes me feel a little better. I don’t think I get significantly better fuel economy with a tailwind. Only exception is that one time I got 23 mpg driving to New Mexico. Think it was 30 mph of wind blowing east or something.

 

[adventureboss]

Takes a second to check live ODB data. I'd check my O2 voltages and fuel trims. That usually tells my brain to shut up when I can see it's all normal.

-Mac

Will do. You just don’t hear people who own other vehicles stating that the wind is reducing their fuel economy. Then again I haven’t driven a vehicle more affected by wind than my softtop TJ. A Honda Element my mother used to own though was also pretty bad.

 

[TJ Jim]

When I used to be broker than I am now I watched every mile per gallon closely. There winter fuel and summer fuel and we just assume if I get x mpg we always get that. Lots of conditions affect mpgs. Just watch for proper running and fault codes.

 

[TheBoogieman]

When I bought my first TJ, I checked the MPGs by filling the tank and running it empty.....twice. I carried a gas can with me for when I ran out. That was 19 Jeeps ago and I haven't cared about gas mileage since then.

 

[lBasket]

When I bought my first TJ, I checked the MPGs by filling the tank and running it empty.....twice. I carried a gas can with me for when I ran out. That was 19 Jeeps ago and I haven't cared about gas mileage since then.

There are better ways to figure out MPGs

 

[TheBoogieman]

There are better ways to figure out MPGs

I needed an exact number (to the last drop) at the time.

 

[JKP]

The 40 and 140 wts cost you a fraction of a MPG. I'd rather have the extra protection, especially at high speeds in high heat. A 40 wt is also allowed more ZDDP than 30 and below, so it's good for the flat tappet cam. If you want to go down the oil rabbit hole, check out the Oil Geek on Youtube. Running 0w-40 and 75w-140 in both of mine.

If the fan is roaring all the time, the fan clutch may be going out. I've had them lock up and become direct drive. That will kill your mileage and it sucks up enough HP that you'll wonder what's wrong with your engine.

 

[KennethS]

You just don’t hear people who own other vehicles stating that the wind is reducing their fuel economy.

Aerodynamics. Wranglers are not aerodynamic; most other vehicles are.

 

[tworley]

You just don’t hear people who own other vehicles stating that the wind is reducing their fuel economy.

Have you driven thru Wyoming?

 

[Strizzo]

Will do. You just don’t hear people who own other vehicles stating that the wind is reducing their fuel economy. Then again I haven’t driven a vehicle more affected by wind than my softtop TJ. A Honda Element my mother used to own though was also pretty bad.

mileage in my lexus GX went from 16-17 normally to 12-13 on the highway in the winds of west texas. My Bronco was similar, went from 16 just about no matter what to like 13 driving into 20mph gusting to 30.

 

[Wheeling diver]

Will do. You just don’t hear people who own other vehicles stating that the wind is reducing their fuel economy. Then again I haven’t driven a vehicle more affected by wind than my softtop TJ. A Honda Element my mother used to own though was also pretty bad.

Try driving a 74 Westfalia VW bus!

 

[TheBoogieman]

Aerodynamics. Wranglers are not aerodynamic; most other vehicles are.

My work car only gets 35 mpg on windy days.

 

[srimes]

Will do. You just don’t hear people who own other vehicles stating that the wind is reducing their fuel economy. Then again I haven’t driven a vehicle more affected by wind than my softtop TJ. A Honda Element my mother used to own though was also pretty bad.

Most people don't pay attention. I've noticed it on high-mpg cars, too. Side winds hurt, even if they're from slightly behind.