MPG from cruise vs you

If I'm in heavy traffic, and not on the highway, I find I get better MPG with cruise "OFF", and I'm more aware of the traffic situations as they arise, but if I'm on the highway (freeway) running at highway speeds (or more) I let the car's computer do its thing w.r.t. cruising, and so far, I've not been disappointed!

 

The hillier it is, the better you will do vs Cruise. I live where it is very flat and cruise is fine (90 feet elevation gain in 154 miles)

 

you might pic up a bit manually, but it's not enough to make it worth the work. i love cc.

 

This depends strongly on the driver and the circumstances. For a competitive hypermiler in hilly country, it is absolutely worth the effort. For most ordinary non-competitive 'just drive it' folks in relatively flat territory, it isn't even close to worth it.

Only you can decide where you fit on that spectrum.

 

I find cruise pretty good, in most situations, can't fault it. I'll just "bail" when I can see an upcoming slow down, or any time letting speed fall off makes sense. I typically don't use it when there's a lot of variables, and/or it's quite hilly.

 

Cruise control does better than I do except in big hills, which we don't have around here. And if it's stop and go, of course cruise isn't practical. But, even if it's heavy traffic, as long as it's flowing well, I'll use the cruise and bump it up or down with the stalk if needed. But my right foot is always ready to spring into action in those situations.

 

The easiest tool is to get a tachometer (such as a Scanguage), and then while driving keep the engine rpm out of the extremes and especially out of the 3800+ range. I have really good luck in holding the engine rpm between 1400 and 3500 driving from Denver to Colorado Springs and back. I loose 10-15mph at the top of hills in the far right lane, but definitely get better fuel economy when doing this drive (probably 2-3mpg) using this method. Also good for the engine life to keep it away from the 5000 rpm redline.

On relatively flat ground I'm not able to notice any difference. I usually use cruise control except when on big hills/mountains, traffic, and passing when on the interstate.

On the interstate, the engine is fairly quiet up to about 3200rpm versus road noise. So if you don't have a tool, just don't rev the engine (or let the cruise control rev the engine) past the point where it just first starts to get noisy (and instead allow the car to loose a bit of speed), and you'll get better fuel economy.

The main reason for this is that the Prius engine is most efficient at about 2000rpm with okay efficiency up to about 3500, and then it drops off fairly rapidly as you get above this.

 

I get trying to squeeze the last bit of mpg out of your car. But.... if there is a lot of traffic, I for one, believe you are being at least as dangerous as a speeder (the other direction of the spectrum) by losing 10 - 15 mph, just to gain "probably 2-3mpg". First, I would be frustrated with the loss of speed. Secondly, (yes, at least you stay in the far right lane, so we can't call you a left lane bandit) you can't help but impeed some traffic with that differential. Again, you do have the right to do that, as long as you are going the "minimum" posted speed, but IMHO, it is not the safest way to travel, for either you, your passengers, or your fellow humans on the road.

I am a newbie to the Prius world. Just been driving this 07 for a couple weeks now. I commented to my wife the other day, that I am shocked how many people immediately start tailgaiting me in the interstate, even when I am doing between 70 - 75. I think they just ASSUME, based on past experience, that I am going to go slower to enhance fuel mileage. some of it you can attribute to them just being a holes. Not all. Probably got stuck behind a hypermiler at some point, and are trying to avoid getting boxed in again.

Again, your right, but think about others.

 

Or you can put your Prius in sport mode and let it rip.

 

Where I drive, there are always some trucks actually obeying the lower truck speed limit (e.g. 60 mph in my state, where cars are allowed 70 mph on the rural interstates) as a condition of continued employment. I would certainly hope that you wouldn't be one of those drivers who accepts such speeds from big rigs but bullies little cars at the same speeds.

As for "probably 2-3mpg" gain, various tests show much greater MPG gains than that:
PriusChat: Updated MPG vs MPH chart:
2010 Prius: Updated MPG vs MPH chart | PriusChat
CleanMPG: Steady State Speed vs Fuel Economy results:
2012 Prius 5: Steady State Speed vs Fuel Economy results | CleanMPG
2017 Prius Prime: Steady State Speed vs Fuel Economy results | Page 13 | CleanMPG

 

I practice what fuzzy has written. The Prius at 3500-4000rpm has significantly more power/weight than a fully loaded semi. The super steep hill between Denver and Colorado Springs has 3 lanes, and I share the right lane with the Semis when going up and don't end up with anyone on my rear bumper due to the other lanes (okay there's the occasional guy who wants to go 90 in the right lane, but that's a separate issue. It's not my problem he can't wait use the left lane). When there's two lanes I'm at or a little over the limit, and I pass plenty of slower cars, so I don't think you can say I'm impeding traffic. No extreme hypermiling from me - I got to get to work on time!

 

Kevin: " I share the right lane with the Semis when going up and don't end up with anyone on my rear bumper due to the other lanes"

That changes everything. Sorry for any insinuation that you were impeding traffic. I bit of a pet peeve of mine, so I probably assumed the worst.

Fuzzy: I don't bully anyone on the highway. 70 mph is not a good time to be flexing one's muscles, in any way. I do, however, go out of my way to facilitate smooth flow. That means I will bump it up a bit to get past a slower car, especially if I can see someone coming up on me. I hate when driver A, going 70.5 mph takes 5 to 10 miles to get around driver B, doing 70 mph. If you can't get by fairly quckly, just stay behind.

 

Not sure what you mean by the "minimum posted speed limits". Most of the speed limits represent the maximum, although it doesn't end up working that way in real life. But nobody should apologize for driving the speed limit on the right hand lane in a multilane highway. If a slower driver strays from the right lane, that's as rude as a speedster refusing to staying in the in the passing lane.

I've seen minimum speed limits posted, and driving that speed would be dangerous, IMO.

 

Minimum speed limits are generally just a warning to people whose vehicles aren't able to go that fast. A car in disrepair, a tractor, etc. They basically tell those people, "If you can't go at least this fast you are not allowed here". That said, if you're not impeding traffic it's ok to be anywhere between the minimum and the maximum.

 

On the interstates if it's fairly level I leave it to the cruise control. If it's rolling terrain at 65 mph (Hwy 395 north of Victorville, CA) my foot is about 3-4 mpg better than cruise. Sometimes it use it, sometimes I don't depending on my mood and the traffic. On any type of a decent climb I always use my foot instead of cruise control.

 

Ok, I've seen these signs here and there. Many drivers consider the speed limit the minimum speed limit and not the maximum- actually some consider the posted speed limit + 5 mph to be the minimum speed limit based on the driving habits I see.

Although California has crazy fast drivers, the trucks have a lower speed limit and stay in the right lanes, the faster drivers usually stick to the left lanes and the carpool lanes. It's when those two territories overlap, that's when you'll see road rage, IMO. I'm a slow driver, but even I get frustrated when I see a slowpoke in the carpool lane, driving slower than normal traffic.

 

I really don't have a problem with slow drivers.... in the right lane.

As for "minimum" speeds, some of the turnpikes in OK (and we have way too many.... you almost can't leave Tulsa in any direction without using a turnpike) have max and minumum posted. I am not aware of any road in OK where trucks are regulated to less than the posted max for cars. Not saying they don't exist, just saying I haven't seen them, and I h ave lived here since 1962.

It is also a violation to “... drive a motor vehicle at such slow speed as to impede the normal and reasonable movement of traffic.” Whatever that is.

Lastly, at least everyone who has posted HERE gets that slower traffic should keep right. It is the law in all 50 states, as well as DC. In addition, in OK, unless you are passing, or moving over for traffic entering from an on ramp, it is illegal to be in the left lane of a limited access highway. Still, lots of idiots over in the left lane doing 60 and making everyone pass them on the right.

Sorry to go off topic a bit. The original question was mileage with cruise, or with your foot. I think there is no doubt you can achieve better mileage with your foot. Dead foot drivers that go "dragonfly" get better mileage than you can on cruise. BTW, that is drag up hills and fly down.

 

Ok, against the law, to obey the law: got it...

Stop the world, I want off.