Doesn't seem unrealistic. I've only had my '01 on one road trip so far, but it returned 31.4 mpg (miles driven / gallons used method), and that was with both trunks full and the top up/ac on at 74-75 mph with a few full-throttle toll booth merges.

Samson,

So, on your road trip, you were able to get around 475 miles between fill ups ? How long can you usually go before you need to fill up normally ?

( Gas tank has a 17 gallon capacity with a 2.5 gallon reserve, so I am guessing most fill up about 15 gallons when they stop )

Nick

The 2.5L cars from 97-98 had 13 gallon tanks and 99 on have a 15.8 gallon if I recall correctly.

I filled up at around 350 miles on each tank, as the other car on the trip needed to fill up more often than I did. I typically had about 1/4 tank or more left, and the car needed around 11 gallons.

I haven't had the car long enough to fill up a "normal" tank, but right now it is sitting just below 1/2 tank w/220 miles. 100 of those were highway; the rest were fun (lots of redline and full-throttle).

I have noticed that the gauge isn't very linear, meaning it will drop from full pretty quickly and hover around half for a while.

James,

Everything I can find on the web says that the 1999 Boxster has a 64 liter gas tank, which is 16.9 gallons...

I have a MY2000 owners manual, and it says the same ( except I know that the 1999 is a 2.5 and the 2000 is a 2.7 so the tank might be different ).

Not trying to be difficult, just trying to figure out how you guys are getting 30 + mpg :

http://www.fueleconomy.gov/feg/noframes/14812.shtml

Nick

I said I got up to 33MPH. It wasn't constant, but I have gotten 450+ miles out of a tank when it was 100% highway and a fairly flat road, plus a passenger and both trunks full, cruising at 72-75MPH in 5th.
My 99' has a 17 gallon tank, and I normally fill up at 1/4 tank left, but on the 450+ tank I waited until my OBC was reading about 12 miles left.

Thanks, guys. Something must be wrong with my car then. Best I have ever gotten on a road trip is 360 miles to a tank :

http://986forum.com/forums/showthread.php?t=5724&page=2&pp=20

Nick

EPA estimates are to be taken with a grain of salt... they aren't exactly real world.

http://auto.howstuffworks.com/28004-epa-fuel-economy-explained1.htm

I've had my IS for about 60k miles, and I've consistently beaten the EPA ratings. They say what, 16/22? I get 20/26, and I don't exactly drive like a grandma.

For the Boxster, I just turned on the cruise and let it do what it does. Nothing fancy there. The car just had an oil change, I replaced the air filter, and the tires were at 36/40 if I remember correctly.

changing the expensive o2 sensors has made a big difference in FE for some.

p.s.
Yesterday I drove for about 45 minutes in the right line going no faster than 52!
Highway was nearly empty (people staying home?). The RPM's never went over 2000. When I looked behind I noticed I had attracted a small convoy, about 4 cars deep. They never pulled over to pass until I exited the Parkway.
Looks like driving slower at the right hour is catching on.

You've got to be running rich if you're only getting 24 mpg on highway trips in the East, where speed is much more tightly controlled than here in the West.

Here's a trip I took:

http://986forum.com/forums/showthread.php?t=15579

I got 24.4 mpg, but over half this drive was in very mountainous terrain, on two-lane roads, where I was driving my car very hard (at least 10 full throttle runs up past 90 mph, during passing), and the rest of it was on freeway, going around 80 to 85 mph. Plus, I have Tip, which takes away at least 1 mpg or more. Oh, and the roof was down for 3/4 of the drive.

17 gal @ 24.4 mpg = 415 miles

The only problem is that it's a GM product. I have a GMC Yukon something odd always going on with a GM vehicle.