Cruising Speed "Sweet Spot"? (for best fuel economy / MPG)

[TFCfan2021]

I think we have almost all seen the speed vs mpg charts posted here, but I am curious if any scan gauge users have found a sweet spot for highway speeds that gets the most speed until wind resistance kills it?

I have been trying to slow down and stick to posted speed limits (45mph on most 2 lanes) but have found 50 to 55 to be higher mpg with a lower engine load, especially for easy rolling hills like we have here in my area.

Anyone else seeing what I am or have a solid speed number?

[BRagland]

I think we have almost all seen the speed vs mpg charts posted here, but I am curious if any scan gauge users have found a sweet spot for highway speeds that gets the most speed until wind resistance kills it?

I have been trying to slow down and stick to posted speed limits (45mph on most 2 lanes) but have found 50 to 55 to be higher mpg with a lower engine load, especially for easy rolling hills like we have here in my area.

Anyone else seeing what I am or have a solid speed number?

I can second your observation.

I live in the peidmont of NC and we have rolling hills here as well. I generally see the best MPG at 50-55 MPH.

I can generally average 55 MPG at those speeds when the hills aren't so steep. Once I get into the steeper rolling hills, I can average about 50 MPG at 55 MPH.

On the High-way doing 65 MPH I can get 48-50 MPG (but less hills).

[TFCfan2021]

I can second your observation.

I live in the peidmont of NC and we have rolling hills here as well. I generally see the best MPG at 50-55 MPH.

I can generally average 55 MPG at those speeds when the hills aren't so steep. Once I get into the steeper rolling hills, I can average about 50 MPG at 55 MPH.

On the High-way doing 65 MPH I can get 48-50 MPG (but less hills).

Going by the speed chart alone it would seem the slower the speed the better the mpg, maybe the chart data was made on a perfectly flat roadway?

Are you downshifting at all or leaving the car in 5th?

[MetroMPG]

Yeah, those speed vs. MPG charts were made on flat roads.

Generally the slowest speed you can cruise while in top gear will yield the best fuel economy.

Wind resistance is the biggest MPG killer in steady speed cruising. And its impact is felt at much lower speeds than most people guess: at approximately 30 mph (50 km/h), half your fuel is being burned to overcome wind resistance. It only gets worse the faster you go from there.

[BRagland]

Going by the speed chart alone it would seem the slower the speed the better the mpg, maybe the chart data was made on a perfectly flat roadway?

Are you downshifting at all or leaving the car in 5th?

I leave it in highest gear.

The only thing that I can think of helping is throwing it in Neurtral going down the hills.

I experimented with that just yesterday and found that on one of my hills leaving it in gear, I would accelerate from 45-55 by the time I reached the bottom; over 3 tries.

In neutral, I would accelerate much faster, going from 45-65 (a whole 10 mph faster) at the base of the hill. That extra speed means more momentum going back up the hill.

I would think, based on that, if one were to throw it in and out of neutral, that you could squeeze an extra 5 MPG easy on the hills in my area.

On the perfect flat areas around me (which ironically, aren't that flat) I can confirm that at 45 MPH I can get close to 60 MPG. But it's not flat enough around me to maintain that 60 MPG consistently.

The best I can get on a consistent regular basis without special techniques other than just being a gentle driver, is 55 MPG consistently when doing 50-55 MPH on the hills or 60-62 MPH on the highway.

Still, 55 MPG is by far much better than anything else I've driven. That's with 1% accuracy calculated at the pump, and on the gauge. So I'm pretty safe to say I can get 55 MPG consistently. My tank average right now sits at about 50.8 over the last 3 tanks.

Though, it's also winter and the gas here has been in the lesser quality for about 4 weeks now, so I'm excited for the spring and summer to come around, as I might be able to get a boost in MPG then as well.

My rear axle toe probably shaves off close to 8 MPG for me, as it's all sorts of messed up and toed in really bad. Once I get that fixed, I could probably see some nice gains as well.

[alex16]

I see the best at 45-50mph with my 5mt

I'll run non eco friendly for the most part Driving to my uber city, it's so strange how I struggled for 35+mpg in my automatic civic and the mirage gives 40 when I race it around, with shifting st 3k and leaving most traffic behind me and getting into the interstate 60mph cruise set I normally end up with 56-58 mpg. 50 psi tires, no ac, no antenna, lowered, eneos sustains oil, led lights. I avg overall around 44-47 per tank

[BRagland]

I see the best at 45-50mph with my 5mt

I'll run non eco friendly for the most part Driving to my uber city, it's so strange how I struggled for 35+mpg in my automatic civic and the mirage gives 40 when I race it around, with shifting st 3k and leaving most traffic behind me and getting into the interstate 60mph cruise set I normally end up with 56-58 mpg. 50 psi tires, no ac, no antenna, lowered, eneos sustains oil, led lights. I avg overall around 44-47 per tank

Nice numbers! A little shocked you're achieving 56-58 mpg with the manual at 60 mph, must be the lowering giving you the biggest boost, along with that no a/c.

[Teasmade]

I concur with previous posters. When I'm bumbling along the motorways of This Sceptred Isle at between 55 and 60MPH I will see around 62-72 imperial MPG (indicated), depending on conditions - obviously that's on the flat and keeping a steady speed. Ambient temperature makes quite a difference.

I'd be interested to see how the manual Euro-spec cars with the taller final drive cope in similar conditions.

[Charlie]

Just chiming in w/ my experiences. I have automatic CVT, and drive primarily for fuel economy. I regularly get ~60 mpg. I find the 'sweet spot' to be around 45 mph, but certainly not anything over 50 mph.

Best thing obviously though for fuel economy? Don't use that A/C!

-Charlie-

[BRagland]

Just chiming in w/ my experiences. I have automatic CVT, and drive primarily for fuel economy. I regularly get ~60 mpg. I find the 'sweet spot' to be around 45 mph, but certainly not anything over 50 mph.

Best thing obviously though for fuel economy? Don't use that A/C!

-Charlie-

I went out today on a fairly flat stretch of road and did 45 MPH on the way to the store in my CVT, and I did actually get better MPG at about 63 MPG.

Unfortunately, 45 MPH results is worse MPG when it comes to hills. Not sure why, but when going over hills frequently, seems an extra 5-10 MPH helps. Probably has to do with a combo of inertia, and engine load at rpm.

Either way, 45 does seem to be the sweet spot for the CVT on a flat road, of which, there are little in my area But for those easy rolling hills, you might be better off at higher speed.