Wind Affecting MPG
 

Have you noticed a significant decrease in gas mileage when driving in high winds? I took a 1200 trip this weekend and the DIC measured 29.5 mpg on the first fillup and 30.1 when I reached my destination. I did a little driving in town then returned home in very heavy rain followed by high winds. The 30.1 dropped to 28 by the time I filled up again and the last tank was 25.1. Yes, I reset everything with every fillup.

Of course, when I got home, I figured the mileage manually. The actual numbers were 27.6, 27.2, and 26.2. Quite a difference, huh! So, it looks to me like wind affects the DIC but not really the actual mileage.

The bottom line is don't believe your DIC!

I've noticed the same in every vehicle i've owned. Engine is having to work harder, less mileage.

Closest my DIC has ever been was 29.6 indicated and 29.1 actual. It's usually 1-2 mpg higher than actual.

Yep...windy conditions affect your mpg especially in a boxy car like a Matrix or a HHR.

Speaking of wind resistance etc...do you think HHRs with roof rails get less mpg than those without? Reason I ask is that some people with roof rails on Vibes were complaining that the rails created noise and their mpg was a bit less than a Matrix which does not have the rails


Goose

I can't imagine that the roof rails and cross bars alone would make too much of a difference. Throw some stuff on the rails and it will start to create some drag.

Goose in my experience it would be the crossbars that would disturb the aero/wind flow over the roof. As a cyclist for years I always saw differences with a Yakima bike rack up there on any car I used it on. In fact I would always have a wind fairing on the front of the rack to direct flow up and over. My PE HHR came with the rails but not the cross bars. Without a wind tunnel test I don't think the basic roof rail position will disturb the flow enough to affect MPG since they are in line with the vehicle direction. Perhaps in a nasty cross wind, yes, but then the side mass of the vehicle comes into play anyway. So that's my unscientific opinion FWIW.

Wilson

Had to laugh when I read this. Not to make fun, just because it brought back memories of a 2.5-hour trip down to Kingston, Ontario. It was headwind the entire way - not light wind either! It was a gusty day with a steady wind of at least 40kph. I was driving a 1985 Dodge Ram w/318cid V8, and I enjoyed fuel mileage half of what I’d normally get. Yep, around 10mpg. It was BRUTAL!

I really noticed it in my 1998 Sidekick and 1985 Jetta as well. What is it with me and boxy cars? I guess I’m a sucker for punishment!

I don't think the roof rails had as much to do with it as the molding around the side windows. Most cars have much smoother transition from the window to the frame than what the HHR does. Several times I thought the molding was going to come off as a windburst hit. Would a stabilizer bar help handling in high winds? We tend to have them quite often in the summer. The semis and motor homes were rolling along at 75mph with little interruption.

"Would a stabilizer bar help handling in high winds? We tend to have them quite often in the summer. The semis and motor homes were rolling along at 75mph with little interruption."

I'd be interested if someone would weigh in on the real world benefits of adding the Progress sway bar (correct me if it's another maker). I too notice the handling issue in the wind. It's windy very often in SoCal as well. It seems to make the HHR feel a bit slippey (as the Rally drivers would say).

Wilson