There are plenty of posts about observed mileage and so on, but my question may be more relevant to highway commuters.

Has anyone experimented with different cruising speeds to measure changes in MPG?

I commute almost 100 miles per day and just got a 2012 All4 with 6-speed. With the cruise set at 78mph I average 28.3mpg (according to the car computer). I plan on trying several different speeds down to 65 to see if there is a mileage sweet spot. Anybody done this? Please include if it's an All4, what type of tranny, and if you're non-US. Thanks!

 

Not a cruising speed, but I installed a boost/vacuum gage, I found that I get the best mileage by keeping the needle in the vacuum range.

Dave

 

So when the car's cruising and not under load, what RPM puts it in the vacuum range?

 

vacuum or boost is all about your right foot and not rpms.

 

my commute to work is 25 miles, with over 24 of that on the highway. I kept it right at 60 and got 36.3 mpg

 

That's not true. If it were then Dave's post would mean he gets the best mileage when his foot is down.

 

Vacuum= negative intake Pressure
Boost= Positive

when you add throttle the Blow off valve closes allowing positive pressure to build to make more power, and less mpgs

when you are off the gass the blow off opens and you get a negative pressure in the intake= better MPGS

both of these can happen at any rpm. the less throttle input it takes to maintain your speed the more Vacuum/ negative Pressure will occur in the intake manifold equaling better mpgs.

there should be a sweet spot though. on most cars it is between 60 and 70 mph. on my r53 the sweet spot is around 65mph

 

I also drive over 100 miles a day. When I'm driving 70-80mph, I get about 29-30mpg but, if I drive 60-70, MPG increases to 33-34mpg. I have a 2011 Countryman S and fill with premium gas.

 

I too, find on my 08 Non S, I average 31.1 when combines with many high mph runs (daily driving), however when I drop it below 68 and rpms drop into the mid 2000s my mpg, slides up to the 35-36 mpg range. I just can't drive that slow

 

From my experience with the All4 manual, 65 is the ideal cruising speed for max mpg.

 

Update: 74mph is 31.7mpg

 

Very nice! This is the two-way average mpg of your 100 mile commute, right?

I'll be doing some checks with my All4 manual after it is broken in. I also mounted a Scangauge, which I will calibrate to actual MPG so I can check the Mini's built-in MPG average for accuracy.

 

my 08 cooper mileage goes downhill if i go over 79 on the speedo(about 74 says the gps) and i average around 32 or so. i've hit as high as 36 on LONG trips, in which i'm taking one on thursday 1500 miles round trip! should be interesting.

 

for me there's a knee at about 3,200 rpm, above which the mileage drops rather suddenly

so I've learned to stay under 70 unless I have a reason...

the difference can be from 33 mpg down to 30 - it's significant I think...

cheers,

Charlie

 

Yeah this is all interestate with the cruise control set. At 6:45 AM there's no traffic so I don't have to brake or change speeds at all. The test distance is actually just over 70 miles. I know the computer is estimating a higher MPG than I get when I measure at the pump, but this way I can restrict the test to only when I'm going the set speed.

 

Update: 70mph is 34.3mpg

 

I think different gas from different stations also would make a difference, maybe the % of ethanol.

Which brand/retailer do you guys use?

 

Chevron or 76 Union 91 octane - CA spec.

 

Thanks, I researched a lot about gas quality from different stations. Many people confirmed that after adding 10% ethanol by law, the mpg significantly drops about 3-5.

And I found that there are no ethanol-free gas station near by, although some states do have ethanol-free gas stations. I guess the mpg manufacturer provided is under ideal condition with real gas (ethanol-free).

I will try to switch to different gas stations to see if that will make any difference.

 

Often, race tracks sell ethanol free premium gas.

Dave

 

In California all gas at regular stations is identical except for detergent additive package. This from a Chevron refinery engineer whom I am related to.

 

Here is what I get with my CMS All4 manual always filed with 91 octane (93 is not available in my neck of the woods.)



I would say I drive about 80% highways miles, mostly getting from the Bay Area to Reno and back again. Those highway miles involve driving through the Sierras going from sea level to 7,700 feet which may not be representative of everyone's highway conditions. The instantaneous mileage drops significantly while climbing. I typically drive 75 to 80 MPH in dry and light traffic conditions.

My in town miles also involve hills whether I am in Reno or the Bay Area. I don't think I'll ever break 30MPG unless I take it on a mostly flat highway trip. That being said, I am OK with the mileage I am getting. The CM is a replacement for a Jeep that barely averaged 16MPG under the same conditions.

 

Update: 66mph is 37.6mpg

This is the largest increase so far as I move down from 78 to 62.

 

Wow!! Over how many miles? What kind of terrain? Standard Cooper / S / All4?
I don't think I could get that kind of mileage even if I drove mostly downhill. I posted my numbers further up and they look pathetic compared to this.

 

86LG4T5 I believe is doing all his tests over his early morning 70 mile commute using cruise control on the highway. Very interesting results!

A suggestion would be to record the temperature and other weather conditions during the run. Wind speed could be a factor, and it is probably getting warmer.