Highway Speed: How Fast is Fast?

mcamp52 · 04-12-2009, 05:31 PM

I have a "new" 2005 and took a 100 mile trip on the interstate for the first time this weekend. I am used to driving cars with tachometers and using that as a way of driving conservatively, without really winding up the car.
On this trip a did a lot of cruising around 70 mph and avoided the temptation to go any faster. Overall, I averaged 47 mpg and I'm cool with that.
But for future reference, does anyone know at what point the Prius is really "wound up" and running to fast? It's not like I want to drive like crazy but I do want to have a feel for not over taxing the car.

**efusco** · 04-12-2009, 05:42 PM

It's fairly linear, you'll see the MPG drop, RPM rise with increasing speed.

**Tideland Prius** · 04-12-2009, 08:14 PM

As Efusco said, it's fairly linear. If it's revving up there, you're probably cloes to 100mph.

KCPrius · 04-12-2009, 08:35 PM

I've taken several road trips and set the cruise at 80 and the engine does not seem to be straining at all. Mileage is in the high 30's at that speed. For what it's worth, I don't like to do a "cruise control pass" of slower moving vehicles going close to the same speed as me, so I will occasionally take it up to 90 to 95 mph. I don't keep it there long, but it still doesn't sound like it's straining at all.

hobbit · 04-12-2009, 08:38 PM

You might be interested in the little rundown on steady-state
highway observations that I just posted over at CleanMPG.
.
I try to never go over 3 grand...
.
_H*

qbee42 · 04-12-2009, 08:50 PM

Mostly the problem is aerodynamic drag. With aerodynamic drag the power requirements go up by the cube of the speed. I wouldn't say it's linear, except in the most crude approximate sense that mileage drops with speed.

Tom

Habeepbeep · 04-13-2009, 01:10 PM

I've had my prius for 5.5 years and have driven up and down the East coast dozens of times. I usually set cruise control at 80-85 when I'm driving on I75 but in one case (fleeing a hurricane) I have reached 97mph. My prius seemed to do just fine and did not have much strain on it (granted it was a few years old at that point). I'm not recommending speeding, I'm just letting you know my own personal experience.

richard schumacher · 04-13-2009, 02:18 PM

"Too fast"? Go as fast as you like. The computers limit the speed to 102 MPH.

mcamp52 · 04-13-2009, 09:17 PM

Thanks everyone. Great answers.

danl · 04-15-2009, 01:39 PM

Too fast for me is anything above 65mph. Only because my commute to work consists of mainly a 2 laner with a 45-50 limit.

04-12-2009, 05:31 PM	#1
mcamp52 Member Join Date: Mar 2009 Location: Central Florida Posts: 32 My Car: 2010 Prius Model: IV Package: Solar Roof Thanks: 1 Thanked 0 Times in 0 Posts Friends: 0	Highway Speed: How Fast is Fast? I have a "new" 2005 and took a 100 mile trip on the interstate for the first time this weekend. I am used to driving cars with tachometers and using that as a way of driving conservatively, without really winding up the car. On this trip a did a lot of cruising around 70 mph and avoided the temptation to go any faster. Overall, I averaged 47 mpg and I'm cool with that. But for future reference, does anyone know at what point the Prius is really "wound up" and running to fast? It's not like I want to drive like crazy but I do want to have a feel for not over taxing the car.

04-12-2009, 05:42 PM	#2
efusco Troll Slayer Join Date: Nov 2003 Location: Nixa, MO Posts: 17,250 My Car: 2004 Prius Model: Package: #9 Thanks: 50 Thanked 261 Times in 157 Posts Friends: 37	Re: Highway Speed: How Fast is Fast? It's fairly linear, you'll see the MPG drop, RPM rise with increasing speed.

04-12-2009, 08:14 PM	#3
Tideland Prius Moderator of the North Join Date: Oct 2004 Location: Canada Posts: 19,633 My Car: 2010 Prius Model: N/A Package: Technology Package (Canada) Thanks: 229 Thanked 346 Times in 245 Posts Friends: 23	Re: Highway Speed: How Fast is Fast? As Efusco said, it's fairly linear. If it's revving up there, you're probably cloes to 100mph.

04-12-2009, 08:35 PM	#4
KCPrius Senior Member Join Date: Nov 2004 Location: Overland Park, KS Posts: 121 My Car: Model: Package: Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	Re: Highway Speed: How Fast is Fast? I've taken several road trips and set the cruise at 80 and the engine does not seem to be straining at all. Mileage is in the high 30's at that speed. For what it's worth, I don't like to do a "cruise control pass" of slower moving vehicles going close to the same speed as me, so I will occasionally take it up to 90 to 95 mph. I don't keep it there long, but it still doesn't sound like it's straining at all.

04-12-2009, 08:38 PM	#5
hobbit Senior Member Join Date: Mar 2005 Location: Bahstahn Posts: 3,626 My Car: Model: Package: Thanks: 0 Thanked 216 Times in 118 Posts Friends: 0	Re: Highway Speed: How Fast is Fast? You might be interested in the little rundown on steady-state highway observations that I just posted over at CleanMPG. . I try to never go over 3 grand... . _H*

04-12-2009, 08:50 PM	#6
qbee42 Senior Member Join Date: Mar 2006 Location: Northern Michigan Posts: 10,492 My Car: 2006 Prius Model: Package: #7 Thanks: 95 Thanked 392 Times in 290 Posts Friends: 10	Re: Highway Speed: How Fast is Fast? Mostly the problem is aerodynamic drag. With aerodynamic drag the power requirements go up by the cube of the speed. I wouldn't say it's linear, except in the most crude approximate sense that mileage drops with speed. Tom

04-13-2009, 01:10 PM	#7
Habeepbeep Junior Member Join Date: Apr 2009 Location: Tampa Posts: 9 My Car: 2004 Prius Model: N/A Package: Base Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	Re: Highway Speed: How Fast is Fast? I've had my prius for 5.5 years and have driven up and down the East coast dozens of times. I usually set cruise control at 80-85 when I'm driving on I75 but in one case (fleeing a hurricane) I have reached 97mph. My prius seemed to do just fine and did not have much strain on it (granted it was a few years old at that point). I'm not recommending speeding, I'm just letting you know my own personal experience.

04-13-2009, 02:18 PM	#8
richard schumacher Destination: Eschaton Join Date: Mar 2004 Location: United States Posts: 5,514 My Car: 2004 Prius Model: N/A Package: #6 Thanks: 100 Thanked 93 Times in 66 Posts Friends: 0	Re: Highway Speed: How Fast is Fast? "Too fast"? Go as fast as you like. The computers limit the speed to 102 MPH.

04-13-2009, 09:17 PM	#9
mcamp52 Member Join Date: Mar 2009 Location: Central Florida Posts: 32 My Car: 2010 Prius Model: IV Package: Solar Roof Thanks: 1 Thanked 0 Times in 0 Posts Friends: 0	Re: Highway Speed: How Fast is Fast? Thanks everyone. Great answers.

04-15-2009, 01:39 PM	#10
danl Senior Member Join Date: Jan 2009 Location: Boston, MA Posts: 164 My Car: 2009 Prius Model: Package: #2 Thanks: 22 Thanked 5 Times in 5 Posts Friends: 1	Re: Highway Speed: How Fast is Fast? Too fast for me is anything above 65mph. Only because my commute to work consists of mainly a 2 laner with a 45-50 limit.

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