What saves more gas?

I'm in the market for a late 80s/early 90s CRX HF. Over 40 mpg city and over 50 mpg highway

 

There is no easy answer on most of this. I don't usually use A/C but if I don't my window is down 2 inches, not wide open like was likely used on mythbusters, enough to blow air on my forehead. An already brick shaped truck probably isn't effected as much by the little extra drag of open windows. At the same time the fuel needed to drive 80 is WAY more than the energy to run A/C, crank it.

I drove from way east Denver back to Boulder at 60 with A/C on since the wife was along and got 37 mpg, I'd certainly have got better without the A/C but happy wife was worth it.

Concerning CC, I've said I use it almost constantly, but I also tap the stalk up/down to adjust my speed with great results. Climbing a hill ease off a few mph as I make the climb and easy back up or neutral, or more likely turn the motor off on the ride down. Unless I need to brake then on with engine braking.

 

I like my 22.5 mpg.

Regardless of mythbusters et al, I'm just gonna keep doing what I've been doing.

 

See my later posts, I clarified that it was an SUV at approximately 55mph. I think it was either a Ford Explorer or Expedition...

 

A/C is priceless on a super-hot day...

 

Absolutely. AC is a must in Colorado (front range)

 

I just concluded my experiment. Sure, I should have done a full week of windows down versus a full week of a/c, but as you will see below, the difference between the two methods is close to nil and the difference between either method and my standard no a/c windows up drive is tiny. Plus, having the windows down messes up my `do on the way to work.

Anyway, in the four days prior to the experiment my commute average (again, using a calibrated Ultragauge) was 21.2 MPG. A few tenths higher than the 20.8 I quoted, perhaps because of the switch to summer blend gasoline. The numbers for the rest of the week looked like this:

Tuesday: 20.7, windows down
Wednesday: 20.7, a/c on
Thursday: 20.7, a/c on
Friday: 20.5, windows down

Bottom line, IMHO, it doesn't matter, do what's most comfortable and if you really care about MPG, just slow down.

 

Very nice analysis.

 

I'm with you MM. Most of my miles are back and forth between CO and OK. I get 22 going to OK and 21 coming back and darn sure use CC (and AC). When I go up in the mountains I still use the cruise on long stretches and when the climb/descent gets too steep, engaging the clutch to shift shuts it off and I take control.

I think the keys to good MPG is to keep your foot out of it as much as possible, be steady and don't be in a hurry.

BTW MM have you done mileage comparisons with your topper on/off? I was worried when I put mine on that it'd hurt my gas mileage. So far no discernible difference. The weight/aerodynamic ratio seems to even out.

 

Makes sense to me. How much do they weigh (roughly)?

 

My topper is on almost exclusively, so I have no comparison.

But from what I've read the difference is nominal.

FWIW this tank I am not using cruise control at all and focusing like hell on hypermileaging. So far a couple of days with the AC on, but it seems to be right on par with my "cruise control" technique or even just slightly less mpg

 

Roughly 200 lbs.

 

I'm not sure that I understand. It's clear to me that at lower speeds with variable driving conditions (terrain mostly), you will experience noticable differences. I imagine that in flat areas, driving with an even foot or with CC probably yields similar numbers. But where you have small to moderate hills, the level loaded foot will prevail.

For me, if I am comfortable with the windows down (cool enough and lower humidity) and I'm traveling under 50 mph, I put the window down, open the slider, and drive with a level foot. If the weather is just too hot, the AC goes on and MPGs go down. Luckily for me, my route to work is shaded so having the window cracked to full open is how I prefer to drive when the humidity is bearable.

Regarding the cap, there was a study performed at a university (you can find the article and discussion at CleanMPG.com) that showed how different configurations of bed covers peformed vs. open bed. Fuller caps provided some of the best 'slip' situations. It could be that at 200 lbs, the cap provides enough slip to compensate for the mpg loss due to the additional weight. Practicality of removing a cap might be enough to grin and bear the FE losses.

 

Mythbusters (take it FWIW) did a show on topper vs no topper. Without the topper bed created a circular wind current (for lack of a better term) inside the bed that allowed for better aerodynamics.

 

Don't drive it!!!

 

Wax her up!

 

walking

 

Thanks Madjik. I did catch that episode and while the show is very entertaining, it's not as scientific as might be needed for some of their experiments. I'll see if I can find the link to the university study in case members here are interested. From what I've read, covers do help. The tailgate down scenario (also tested by Mythbusters) appears to make sense, so those driving with the grills and nets for FE purposes are probably not going to see anything. Bottom line though, folks need to be happy, so picking what makes them happiest should eleviate the need to bang their head.

Kevin

 

It looks like some of the links have gone broken, but here is some of the links to discussions if interested. The second link has a clipping from Texas Tech's study on bed configurations and what works best.

http://www.trucktestdigest.com/TTDfeatures/FeatureTailgateUporDown.htm

http://www.cleanmpg.com/forums/showthread.php?t=41763&highlight=cover+vs+open+bed&page=2