WC Archive

I discovered on experimenting on a few road trips that my subaru got good mileage when i drove slow. I drove one tank at 50 miles/hr through Kansas and got 35mpg when normally I would get maybe 28 driving normal speeds on the highway. its a much more sane pace also!

The sweet-spot for my 2003 HCH has been at 80km/h on roads sign-posted 80km/h. On two such trips I averaged 4.0L/100km and 4.2L/100km; works out to 58.8mpg and 56.0mpg respectively.

Now if only someone could come up with a tweaked cruise-control to use this technique automatically...

The sweet-spot on most cars is 80-110km/h or 60-80mph because they're not designed like bullets (to have a very low resistance profile) - at these moderate speeds the air resistance is kept at a minimum so the engine does not need to work hard to keep the momentum up. The amount of power required to maintain a higher speed is exponentialy higher than the equivalent gain in speed.

Put on some sweet tunes and enjoy the ride.

And if you drive a bullet-shaped sports car (pedestrians beware!), you can cruise at a higher speed for the same fuel economy :)

With a diesel engine I seem to get over 50 mpg (but note, those are UK gallons) at any speed from crawling to 75 mph. If I keep the speed between about 30 and 60 then I get about 60 mpg. Above 75 (not that I would drive that fast, of course) fuel economy drops sharply.

Our old econline ford van normaly got 6-8 mpg but it went to 20 if driven at 75 mph. Tank of a van that one was heavy as hell and 2 33 gallon gas tanks gave it great range on a fillup.

http://amazngdrx.myblogsite.com/blog/_archives/2005/8/9/1120557.html

Hard to believe but true! GM manufactures a $5000 43 mpg minivan in China.

But rather than sell it here...they pushed the guy who pioneered the effort in China for them to resign.

The same wacko execs who sent GM bonds into junk status. Why was this inovator not made CEO instead? Because US auto companies are run for the benefit of big oil? That's my guess.

Actauly they cant sell it here as no one could sit in it;/ The seats are that small. Its a very small van made for very small people.

As for them firing him they didnt they downsized and we wound up too close to management for his comfort so he resigned. I have seen that effect before. It doesnt even have to mean anyone even so much as poked him even.

As one of the drivers of the Prius mentioned above, let me add a few facts and a thought or two.

The course was 30 miles round trip, including 31 traffic lights and a couple of moderate hills. Our speed was mostly in the 30-40 range using the pulse and glide technique, sometimes a little slower. The gas engine was on only 27 percent of the time.

While our efforts were a bit extreme, admittedly, there are three primary lessons any driver can use to improve their fuel economy:

Slow down. Whoever posted above that cars do best at 60-80 mph is very wrong. Every vehicle on the road will get better economy at the speeds we drove. So whatever speed you normally drive, if you knock a little off you'll get better mpg. Rather than trying to keep up or beat other traffic, try driving as slow as you can to avoid being a nuisance to other drivers.

Minimize your need to brake. By anticipating the need to slow or stop and taking your foot off the gas sooner you'll save valuable fuel.

Keep you tires pumped up to the sidewall maximums, not the car maker reccomendations. This will save another 2-5 mpg.

All of the above is about choices. You can choose to drive to achieve your goals. If saving gas means more than saving time to you, maybe this will help.

Dave Bassage

Say what you will our old van ALWAYS got by far its best gas milage at 75 mph.

Did you ever try driving that same van an entire tank at 35 mph? I grant that peak efficiency can vary from one car to another, but would need to see it with my own eyes to believe any vehicle gets better mpg at 75 than 35.

Just my perspective,

dave

Last summer, my 2003 Subaru Forester with a 5-speed manual transmission was getting about 37 mpg (city/highway combined). In the winter it gets about 34 mpg. This summer it is getting 38-39 mpg. The engine friction losses exceed both the tire rolling resistance and the air drag below 35 mph, so I get good mpg by keeping the engine speed below 2000 RPM, and not using the air conditioner. The engine efficiency is maximum at about 30% of redline and about 80% of maximum torque. The secret for getting high mpg is to minimize the engine revolutions per mile.

Overdrive... our econline ford had a very agressive overdrive gear. When it kicked into overdrive the engine noise vanished entirely and all you could hear was the wind.