If MPG drops, check PSIs more frequently!

[NY Smartie]

I have an easy to use digital tire pressure gauge. it's small, and works great. good investment.

[stevenvillatoro]

Originally Posted by SharonRB

I think the rears were way down and the fronts were down by a pound or so.

Interesting... you'll note that it was MY rears that were way down (4 PSI off), too. Fronts had not lost as much air.

[WickedMessenger]

Originally Posted by SharonRB

I rarely use my AC -- I have the top down all the time unless it's raining. I did have to use it a little bit this weekend, but not much.

Hubby checked the tires for me last night, and I definitely needed some air. He said a couple of the tires were down 5 lbs. Hopefully that will help, although I did get 41 miles on the fifth bar, most of which was driven before airing up.

Convertibles with the top down have a coefficient of drag (Cd) about twice that of with the top up. Already the smart's Cd is a not-so-good 0.31. You would be MUCH better off using the AC than driving with the top down over 40 mph. Wind drag increases exponentially with speed, not so with rolling resistance.

[SmartShanna]

ooh, I've had my car since March and haven't once checked the pressure in the tires

[SharonRB]

Originally Posted by WickedMessenger

Convertibles with the top down have a coefficient of drag (Cd) about twice that of with the top up. Already the smart's Cd is a not-so-good 0.31. You would be MUCH better off using the AC than driving with the top down over 40 mph. Wind drag increases exponentially with speed, not so with rolling resistance.

I know my mileage would be better with the top up, but I've consistently had it down and all of a sudden got the drop in MPG on my third and fourth bars on this tank. My last tank I got 39.7 mpg overall and I've been doing similar driving on this tank under similar circumstances.

I'm not convinced that I'd be better off with the AC on (I did have it on a little bit this past weekend because it was rainy and very, very muggy). Besides, it's much more fun to drive with the top down.

[smart teacher]

Originally Posted by SharonRB

I rarely use my AC -- I have the top down all the time unless it's raining. I did have to use it a little bit this weekend, but not much.

Hubby checked the tires for me last night, and I definitely needed some air. He said a couple of the tires were down 5 lbs. Hopefully that will help, although I did get 41 miles on the fifth bar, most of which was driven before airing up.

Sharon, I could be wrong, but I didn't think the 'bars' were linear. In other words, I don't know, or didn't think that bars necessarily equated to a certain defined number of gallons or level of fuel in the tank. I thought it was more of a 'guestimate'. Someone correct me if I'm wrong.

[smart teacher]

Originally Posted by WickedMessenger

Convertibles with the top down have a coefficient of drag (Cd) about twice that of with the top up. Already the smart's Cd is a not-so-good 0.31. You would be MUCH better off using the AC than driving with the top down over 40 mph. Wind drag increases exponentially with speed, not so with rolling resistance.

Awww, but that takes the fun and theraputic value away!