What speed is the Sonic most efficient at?

[HotBoxer]

Has anyone experimented with different speeds to see what gives the best MPG?

Today I was able to average 5l/100km (47MPG) with my cruise control set to 100kph(62mph) on the highway. On completely flat road it went as low as 4.2l/100km(56MPG). This is on a 1.4T Auto in 6th gear.

 

[nickalltogether]

I think for me if I could do 45-50mph in 6th gear on flat I'd get similar to you with my M6 1.4T.

 

[pbkn1p]

The most I've gotten is a steady average of 37.1 mpg in 90% hwy driving. This is what it's showing on the display I'm usually at 70 mph for about 30 miles. And 55 for another 25 miles. Lately I've been trying to slow it down by 5 mph on my commute. This is running regular 87 gas.


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[nickalltogether]

The most I've gotten is a steady average of 37.1 mpg in 90% hwy driving. This is what it's showing on the display I'm usually at 70 mph for about 30 miles. And 55 for another 25 miles. Lately I've been trying to slow it down by 5 mph on my commute. This is running regular 87 gas.


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My mpg is all over the place above 70mph. Drove a 3.5 hour trip at about 75mph last week, got 36mpg. Filled up and then got 32mpg on the way back. Flat trip, very little elevation change either way.

 

[Natesriv]

anything below 70mph IMO... after that you're pushing harder...

I'd say probably 40-55 with the windows closed... however, at that speed you'll get run off the road!

 

[pbkn1p]

Well since I work very early I don't have that worry about keeping up with anyone or being ran over by a truck. So I do have the luxury of slowing down a bit on the way to and from.
I've read a lot about how premium gas does nothing for mpg on stock tune. But I read somewhere that plus is the way to go. So I will try that next tank full. the computer says the average but the mpg per tank is steady at around 35 at fill up. By calculation of course.

Now I do have the RS with a manual. So I also try to shift at 2.5 rpm.


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[Natesriv]

I run e091, no ethanol 91 octane. I get 3mpg better with it, offset by the higher price though.....

 

[eggsalad]

In theory, you would want the lowest speed achievable in the highest gear. Manual transmissions are best for this; automatics will often force a transmission kickdown.

In my 1.8/M5, the upshift light for 5th will come on at about 29mph on a level surface. Given the right conditions - level ground, low elevation, no wind, one could probably achieve 60mpg at 29mph.

This summer, I did a lot of back-road driving at around 45mph. I saw at least two tanks at 47mpg average.

However, there really aren't any real-world conditions at which one could safely drive 29mph for long distances.

 

[mitdr774]

My personal best was a 350 mile trip with 95% highway at 60 MPH and a calculated average economy of 51.92 MPG. Not bad for a 1.8/5MT.

Every vehicle will be different and will require experimentation to find the ideal speed. Generaly 60 MPH is a decent compromise between speed and economy though.

 

[HotBoxer]

In theory, you would want the lowest speed achievable in the highest gear. Manual transmissions are best for this; automatics will often force a transmission kickdown.

In my 1.8/M5, the upshift light for 5th will come on at about 29mph on a level surface. Given the right conditions - level ground, low elevation, no wind, one could probably achieve 60mpg at 29mph.

This summer, I did a lot of back-road driving at around 45mph. I saw at least two tanks at 47mpg average.

However, there really aren't any real-world conditions at which one could safely drive 29mph for long distances.

Thanks for this informative post. I tested this and found that the automatic transmission will allow me to shift into 6th at 70kph(43mph), and will not force a downshift into 5th unless I go down to 65kph(40mph). Setting cruise at 70 seems to work well.

 

[Palmaris]

In my unofficial testing I have determined that its pretty much the lowest speed possible in 5th gear (or 6th for you lucky ones). Of course you won't go anywhere unless its flat or downhill anyway.

But I would say that generally you'll get better mpg at 50 mph than at 60, and once you start going higher speeds then it really has an effect.

 

[mja]

Just got back from a road trip from Houston to Austin. Was excited to finally see 50mpg on a tank, I usually cruise around at 55mph.

Nope. Too many hills over in central Texas killed the mpgs, 95% highway driving I returned 45 mpg :blankface: I have a feeling cruising at 60mph wouldn't have affected my overall mpg for that trip.

On Houston's flat ground I easily see over 45 mpg on a tank with about 60/40 city/hwy driving. Have seen 49-49.8mpg's but never 50mpg yet.

 

[tdiller]

Has anyone experimented with different speeds to see what gives the best MPG?

Today I was able to average 5l/100km (47MPG) with my cruise control set to 100kph(62mph) on the highway. On completely flat road it went as low as 4.2l/100km(56MPG). This is on a 1.4T Auto in 6th gear.

I would suggest that it's not so much a speed at which you get the best gas mileage rather it's at what rpm. I've found that at or just below 2000 rpm is where I get the best gas mileage. That puts me right about 60 mph most days. I've tried maintaining speed but I've found that maintaining rpm seems to affect the mpg better.

 

[mja]

I would suggest that it's not so much a speed at which you get the best gas mileage rather it's at what rpm. I've found that at or just below 2000 rpm is where I get the best gas mileage. That puts me right about 60 mph most days. I've tried maintaining speed but I've found that maintaining rpm seems to affect the mpg better.

The near 50mpg tank's (best mpg) I've had have been at the lowest revs - under 1500 rpm with the 6 spd.

Weather + terrain plays a huge factor for applied engine torque vs mpg.

 

[HotBoxer]

Yeah I can get close to 50MPG in 6th gear with my RPM very low, around 1200.

 

[bluejay]

not sure what my mpg is but i think when im doing 65km/h at 1500 rpm in 6th is when my car is most efficient . or highway @110km/h at just under 3000rpm.

 

[benkanobi]

I drove our 2018 Corolla to Indiana and back in 2018- I set the radar cruise control to 65 and stayed in the right lane- sometimes I had to go around a slow truck. My 2300 mile trip averaged 40.4 mpg. I think the EPA highway is 37 .
I sold a 2009 Chevy HHR last year and my best was 31mpg- normal highway was 28-30, IF you set the cruise control- if not, the mpgs were 1-2 less at the same speed. --2.2L 4speed.
I suspect the engine is leaned out a bit more when the cruise is engaged, that is why the mpgs are better.
My 2.4L, 4 speed auto, Honda Element gets around 22mpg mixed driving- the Chevy Avalanche I sold last year after 2 months got 13mpg- 15 on the interstate at 75-80.
My 1984 diesel Chevette 5peed MT, could easily get 50 mpg - almost 60, if you drove the then legal 55 mph speed limit.