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Hi all
I have enjoyed this forum for some time now. It looks like we will get our 08 red prius Monday or Tuesday.

I have lots of questions but I will only ask one for now. I currently use my cruse control most of the time on our 03 Impala and get excellent gas mileage (around 31-32) on the hwy.

Will I get mid 40's with the cruse control on or is it better not to use the cruse ?

Thanks
Chuck

Answer is: It depends.

First, let's talk interstate highway driving. The potential downside to CC is that it is very aggressive in trying to maintain speed. In hilly terrain it easily pushes engine RPM into inefficiently high ranges. On flat terrain, however, that generally is not a problem. On the flat or downhill, CC can allow RPM to drop into what some consider to be, at least theoretically, inefficiently low ranges.

There are methods of driving that will keep RPM in efficient ranges, but they require continuous adjustment of the go-pedal. I did a controlled test comparing CC to one of those methods. You can read the test report here:

http://priuschat.com/forums/knowledge-b ... prius.html

My conclusion: On flat or gently rolling terrain, CC is just as good as the alternative method, and a lot simpler. In hillier terrain, however, I tend to stick with active manipulation of the go-pedal.

Next is the "mid-speed" ranges of, say 45-55 MPH. The same can be said of CC as compared to the method described in my paper. However, there is another advanced technique that probably can net better fuel economy on terrain that is flat or nearly so, but it takes practice and probably is best done with add-on instrumentation. And it is not practical at interstate speeds. It has been dubbed "super highway mode," and a thorough discussion can be found here:

http://www.cleanmpg.com/forums/showthread.php?t=6179

Finally, at speeds of 40 MPH or less, I avoid CC. Instead, a technique known as "pulse and glide" will net better fuel economy when it can be applied. There are lots of threads here and in other forums discussing the technique, but to get you started, this is probably the most complete:

http://www.cleanmpg.com/forums/showthread.php?t=1224

Good luck!

I have the 'old' Prius. On the freeway or around town, I consistently get around 48MPG. I don't use cruise control because my commute is all stop-n-go. We live in California and the freeways and streets are almost completely flat, so perhaps my example isn't a good one. The trick I've found is to put lots of space between you and the person on front of you. If they start slowing down, let off the gas and let er' cruise as much as possible. This way you're letting the wheel generator motors recharge the batteries. You'd be surprised at how much you can do this. That seems to make the biggest difference for me.

There's other things to consider. We live in a mild climate, which is most ideal for these cars to get the best fuel economy. Colder climates tend to zap the economy a bit. It seems like the going rate is indeed around 45MPG for these cars.

I do better with the CC... it helps me keep my speed down where I can get better mileage and annoy the other drivers behind me. Without CC I tend to creep up to the 10+ MPH over the limit like the other idiots out there, who are all complaining about the price of gas.

For steady speed interstate driving your best mileage will be achieved with the cruise control.
If you can keep your speed at 60 MPH, your Prius will reward you with results at or beyond
60 MPG! Drive faster, and your interstate mileage goes down.

Slower speed driving, and variable speed driving is best done without cruise, employing driving techniques that are efficient and exploit the amount of time the gas engine is not running . Glide, stealth, warp stealth. Research those terms and techniques and you can exceed this car's original EPA estimates of 60 MPG, and 600 miles per tank. I do it, every tank.

One nice, summer day, I drove North through central Alabama - speed limit 55 and lots of small-town cops on the road. I set the cruise control at 55 and enjoyed the day. When I got to my destination, the MFD said I had an average of 60.4 mpg. More recently, driving through a long construction area with speed limit of 45, the MFD said I had a 5-minute average of 70mpg. It looks like slower is better

I try to keep my cruising speed at 57 or 58 mph, except when I am in the carpool lane, where I will do 70. If that lane is going faster, it usually means I can do at least 50 in the regular lanes.
I do use cruise control when traffic permits. My overall average is around 54.5 mpg, figured by using actual gas purchased. The MFD usually shows around 56 or 57 at either in town or my lower speed freeway driving, but I think it is a little optimistic.

JimboK and others thanks for all the info.

I have put 824 miles on this little Red beauty so far. After reading many post i have tried P&G and i think i have been successful. I got 483 miles out of the first tankful with 2 bars left. The second tank full gave me 51.8 MPG. The MFD MPG matched the calc MPG on the second tank full so i am very happy so far with this little Red beauty.

I have not seen many post on what gas is being used (non ethonol or 10% ethonol). In our area the non ethonol is 87 octane and the 10% is 89 octane.

My question is what do most people use non ethonol or 10% ethonol ?

Quick answers (though, just my opinion):

Cruise control -- All the time, city, highway, mountains and on the flats.

Ethanol -- I buy whatever is the cheapest.

Mileage last fillup was 56.5 mpg. However, it will be 100+ degrees in the next few days, and fuel economy will drop to mid- to high-40's in mostly city driving.

I drive a 2002 Prius, and I am currently running 46/44 psi in Michelin HydroEdge tires. Dropping to 44/42 psi, drops mileage about 2-3 mpg.

[quote="Chuck41"]JimboK and others thanks for all the info.

I have put 824 miles on this little Red beauty so far. After reading many post i have tried P&G and i think i have been successful. I got 483 miles out of the first tankful with 2 bars left. The second tank full gave me 51.8 MPG. The MFD MPG matched the calc MPG on the second tank full so i am very happy so far with this little Red beauty.

I have not seen many post on what gas is being used (non ethonol or 10% ethonol). In our area the non ethonol is 87 octane and the 10% is 89 octane.

My question is what do most people use non ethonol or 10% ethonol ?[/quote]

In some states like California, you don't have a choice. All gas has to be "oxygenated" which requires use of MTBE or ethanol. The former is a known carcinogen, while the latter is mainly from Archer Daniels Midland, the big agro-business. So the People's Republic of California MANDATED using MTBE! (Heaven forbid that a company make a profit.) Finally after about 10 years, it was replaced by ethanol.

I am presently running a series of trials on a flat 5-mile stretch that I drive every day, using pulse and glide one day, and cruise control, attempting the same average speed. Average speeds are 20-30 MPH. Preliminary results indicate that CC is as good as P & G most of the time. Optimal P & G, when everything is done just right, is better then CC.

I will be presenting the data and more conclusive results at HybridFest this year.

It doesn't happen often, but sometimes my car goes into glide mode on its own while the cruise control is engaged.