Drove 2000 RPMs on the highway for 1 hour

Perfectlap, how fast were you going in 6th gear to only have 2100 RPM.

In 6th gear, at about 65-70 mph I am right at about 3,000 RPM.

[pbanders]

Why go slow!?! I drove up and back from Phoenix to our place in Flagstaff last week in my M3, windows up, A/C on. Door-to-door it's 175 miles, with only about 10 miles of the drive not on the freeway. You gain about 6,000 feet in elevation going to Flag, total climb with the ups and downs is probably around 8,000 feet.

I made one stop going up, my average speed overall was 67.1 mph, and I got 24.5 mpg. Coming back, I averaged 70.8 mph and got 29.7 mpg. I'll bet the Boxster with the roof up would have beaten these averages.

If I'd done as Perfectlap did, I probably would have gotten a few more MPG, but a much lower FPG

[rick3000]

I do a lot of city driving (I hate it), but whenever I'm on the freeway in fifth at 2900-3200RPM my gauge never moves. Occasionally it will go up a few miles, because I'm getting better mileage.

I just don't think you'll see a huge difference cruising at 2100RPM, except maybe some premature engine wear from things building up in the engine. There was a thread a while back, that explained the going to 5000RPM is good for the car because it cleans the engine out.
Plus, going slow is just no fun!

[Brucelee]

There was a thread a while back, that explained the going to 5000RPM is good for the car because it cleans the engine out.

Well, that is an interesting opinion. Facts would be interesting.

[rick3000]

Sorry, about not recalling all the facts, but the buildup I was referring to was a carbon buildup in the engine, that higher RPM's get rid of.

Here's the thread, and the long debate that goes with it:

Keep her above 4000rpm and she'll thank you for it every day.

[986chris]

so a couple of weeks ago I took the forums advice and started burning prem. in my truck. 03 silverado 8.1. so my commute is about 5-7 min. at 35 mph. my computer avg. mpg has dropped about 2 mpg since I started this short drive. when i,m driving it shows my instant avg is 6-8 mpg which seems odd given the low speeds. anyone help me clarify this, is the computer correct, or is the data gathered effecting the outcome. dosen't matter much since my fuel bill is now $25 a week.

[JCL12]

While driving slowly on the highway I've gotten 29.1 MPG from a 01 tip box. (Odometer mileage divided by gas fill). I would expect newer boxes to hit 32+ easily.

[Dr. Kill]

Yes, I have achieved 31MPG on the highway just by driving 65-70 in 5th gear without hard acceleration.

I am under the impression that one could attain better fuel economy with the top up and the AC on than with the top down and not running the AC.

[2000SoCalBoxsterS]

Originally Posted by 986chris

so a couple of weeks ago I took the forums advice and started burning prem. in my truck. 03 silverado 8.1. so my commute is about 5-7 min. at 35 mph. my computer avg. mpg has dropped about 2 mpg since I started this short drive. when i,m driving it shows my instant avg is 6-8 mpg which seems odd given the low speeds. anyone help me clarify this, is the computer correct, or is the data gathered effecting the outcome. dosen't matter much since my fuel bill is now $25 a week.

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

[Brucelee]

Originally Posted by rick3000

Sorry, about not recalling all the facts, but the buildup I was referring to was a carbon buildup in the engine, that higher RPM's get rid of.

Here's the thread, and the long debate that goes with it:

Keep her above 4000rpm and she'll thank you for it every day.

Thanks. I will check it out.

[jmatta]

I have a second home in Wisconsin about 125 miles from where I live. When traveling back and forth on the weekends, my Box S has far better fuel economy than my Grand Cherokee, even at premium prices; not to mention the fun factor!

(Another statement by Capt. Obvious...it's what I tell my wife so I don't have to haul stuff back and forth).

[Perfectlap]

Originally Posted by bmussatti

Perfectlap, how fast were you going in 6th gear to only have 2100 RPM.

In 6th gear, at about 65-70 mph I am right at about 3,000 RPM.

The speed limit on the Parkway here in NJ is 55. I pretty much stuck to it (saw two people get pulled over by the troopers). It really amazes me how fast people drive while they cry about high gas prices. The average speed was 20-25 miles over the limit and I'm sure the passing lane was well above that.
IMHO opinion the Roadster experience isn't that much different at 60 then at 80.
As a matter a fact at highway speeds I see no difference between any rate of speed until you go over 90+. I guess driving faster than you need to is like passing by a free buffet after you had dinner at home, 90% of Americans will eat a sandwich off the buffet even if they aren't hungry, simply because they can.

Most of my miles are done on the Parkway, I think I'm going to employ the "sticking with speed limit" tactic and see how much less I'm spending on gas over the next few months. If I want to stretch the BoxsterS' legs I go to the autocross 10 minutes away. It would be great if the Boxster had an electric back up for highway driving that you could remove and go fossil fuel during real hp driving. I'm way to frugal to blowing $60 on a tank of gas. This bs is getting crazy.
And that's coming from a guy that only drives weekends.

[fatmike]

If you've ever driven a Prius -- you wouldn't wish for a battery hybrid system in the Boxster. The Prius is, without a doubt, the worst handling car on the road. The batteries add mass and moment of inertia that is borderline unstable.

I would rather see Porsche focus their efforts going forward on building a lighter car. That will result in both better handling and fuel economy. A hypothetical Boxster that weighed 2000 lbs would have excellent performance from a 2.5 liter Direct Injected engine. It might also get 35 mpg+ on the highway. That would make the ideal daily driver for me...

[rick3000]

They have (almost) already done that!
I've gotten my 2.5L up to 33MPG on the highway. And if you stripped it, you could probably get 35+ MPG.

I would dare to say that the most wasteful use of gas on the highway is used while accelerating. Cruising at a lower RPM might help on long trips, but I think the best way to save on the highway everyday is to stop enjoying the onramp and revving to 6000k.
Although, this hasn't stopped me, yet!

[NickCats]

Rick,

33 mpg ? Are you sure about that ?

Our 2.5L have a 17 gallon gas tank.

So, are you saying you can get around 500 miles on a tank of gas ?

Your car must be magic. I get around 300 mi before the light comes on...

Nick

[pbanders]

I would think that 33 mpg for a 2.5L being driven at 60 to 65 mph on a flat highway is not surprising. Of course, you might die of boredom, but hey, at least you'd be getting good mileage.

[rick3000]

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.

[Samson]

Originally Posted by NickCats

Rick,

33 mpg ? Are you sure about that ?

Our 2.5L have a 17 gallon gas tank.

So, are you saying you can get around 500 miles on a tank of gas ?

Your car must be magic. I get around 300 mi before the light comes on...

Nick

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.

[NickCats]

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

[TriGem2k]

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

Originally Posted by NickCats

Rick,

33 mpg ? Are you sure about that ?

Our 2.5L have a 17 gallon gas tank.

So, are you saying you can get around 500 miles on a tank of gas ?

Your car must be magic. I get around 300 mi before the light comes on...

Nick