Got back today from a 3 day trip to Vegas. On the way up, got 29mpg keeping it under 70.
On the way back, did 80-90 the whole way, got 32. What's up with that?

 

2 words

power band

you made it easier for the engine to maintain that speed

 

you were traveling down hill the whole way back
tail wind maybe?

 

or your math was off...aha jk

 

I'll go with tailwind and down hill

 

There are some good hills on the way back. The longer version of the story is I was passed by a G35 sedan doing 80ish outside Boulder City, NV , where I had just gotten gas, so I fell in behind, letting them run interference. I stopped in Kingman as I had to clean the windshield again, and fell in behind a BMW X5 doing mid to high 80's. Stayed behind them, sometimes far behind until Wickenburg when we (my wife and I) stopped for lunch. That's where I got gas again and tallied it up. I was in 3rd gear a lot. Suck that the AC cuts out at WOT too.
And, there's only about 1000 feet elevation change between Vegas and Phoenix.

 

The laws of physics bow to the awesomeness of your ride? More likely a short fuel fill that's going to bite you the next time you fill. 80-90 in third gear isn't possible, is it?

 

I can go from Salinas Utah to Vegas on a tank.....

 

I wouldnt wanna try 90 in 3rd gear in my B...no way

 

only if you want a ventilation hole in the engine block

 

Yahoo maps says that's 383 miles. My best tanks are something like 552, 554, and 621 miles.

Our MT xBs turn 4500 rpm @ 90 mph in 5th gear with our overall 3.53:1 gear ratio. 3rd gear is 5.65:1, which would have the engine turning 7200 rpm. Unfortunately for ajayaitch's credibility, our engines redline at 6500 rpm. If he took his engine to within a hair's width from destruction ;) at 6400 rpm in 3rd gear, he could get 80 mph out of it.

 

^^ yea, but I was getting gas every 250 miles when I made the trip. and then I thought my gas gauge broke

 

You guys are harsh.
Fortunately, I don't really care if you believe me or not, but I'll throw a couple points out there anyway.
I've been driving this car for 4 years. I'd like to think I know it pretty well. My fuel gauge is sitting at half tank at 170 miles. It doesn't mean I have half a tank, that's just what it shows. This has been consistent for the last 45,000 miles. During this run, when we were coming into Wickenburg, the gauge was just under 1/2 at 190 miles. Today, I have 150 miles on the current tank, the one I got in Wickenburg, and the gauge is over half tank. I did not get a short fill. Yes, I know it's not accurate or scientific, but please, STFU.
SentraSE-R, I have absolutely no doubt that your math is correct. Too bad it doesn't apply to my car, since it's an automatic. With 195/60-15's, I'm only turning 5200 RPM's at 90mph in 3rd. This is assumng the sites I got the 3rd gear ratio of 1:1 and final drive of 4.15:1 is correct.

 

The gearing is correct, the 5200 at 90, not so much...

I knew I had this laying around... see, at the 1320 mark on a drag strip I was bouncing off the rev limiter in 3rd... which, as the video will show you, is not 90MPH... In 4th that is plausible, but I no longer have the xB here to test that theory

http://www.streetfire.net/video/her-...e-in_69553.htm

 

You figure it out then. Personally, I don't see how simple math can be wrong.

I'm running 195/60-15's, 24.2" diameter
http://www.miata.net/garage/tirecalc.html

This is the site I used for the RPM calculation
http://www.apexgarage.com/tech/gear_ratios.shtml
Here's some more...
http://www.angelfire.com/fl/procrastination/rear.html
http://www.f-body.org/gears/
http://www.kabamus.com/garage/gears.html

So tell me, what RPM was I turning at 90MPH in 3rd?

 

Heres an idea... grab your camera and car keys. and go test your theory... because I dont know what you did wrong, but its wrong...

Also, if your gonna try to spread BS here on SL... we have a place for that, its called the tC owners lounge...

 

I was off by 500RPM, sue me.

http://www.youtube.com/watch?v=rFqns2PAWzs

 

Since I questioned your gearing, assuming you had a MT, I agree your rpm figures are correct for ATs. It is possible to go 90 mph in 3rd gear with a 1G AT. Now prove you can get 29-32 mpg at those speeds ;).

 

Well, I will say, after watching the video a couple times (because the starting of the video with the car moving made me second guess myself) I will say bravo, as you have done something not a lot of people (with these cars) have done, and thats prove me wrong.

Although I blame it on my lack of knowledge of the auto transmission vehicles

My hat goes off to you sir...

 

Ditto. I'm not a slushbox fan, either.