OK, now that I have the tank size down, thanks to everyones help, what's up with the gas gauge. We have a cooper, and we are getting around 31, 32 with a lot of city driving and a little highway. Not as good as I had hoped, but not horrible either. I will make my final judgement when the wife lets me drive the car for a week straight and I can do the math myself. Right now she has been resetting the ODO to see how far she runs, so I have to guess how much gas went in (she throws out the slip) and the first tanks mileage =~ the actual ODO more or less, and this on is the second tank so just sub out the 325 from the first one... After this it will get harder.

Anyway, from what I have seen in the limited amount I get to drive the car, we get about 200 miles in the first half of a tank and around 100 in the second half. Is this common? It seems to me like the half mark is more or less the third left mark... maybe I will find out when I can pump the gas myself to see how much actually goes in, but I'll see....

Love the darn car though, I just need a wife that will share.... I called the MINI dealer in the Hamptons today about their 20 MCSs that are avaliable and what they will give me for my 04 wrx.... no response yet...

Ben

 

I'm getting about 125 on the 1st 1/4, about 150 on the next 1/2 and about 50 on the last 1/4.
Makes it real hard to plan. :evil:

 

I read a while ago that such behavior is normal on newer cars lately.. some engineers studied a focus group that said that consumers expect a gas gague to work that way or something like that...

Rocketboy_X

 

Who would expect the gas gauge to be wrong.... Must be ford drivers or something....

 

>>OK, now that I have the tank size down, thanks to everyones help, what's up with the gas gauge. We have a cooper, and we are getting around 31, 32 with a lot of city driving and a little highway. Not as good as I had hoped, but not horrible either. >>>

WOAH, let the engine loosen up a bit ... not that 30 mpg around town isn't pretty good, but you've got less than 1000 miles on that right? Most cars truly finish "breakng-in" by about 10000-15000 miles, that's when fuel economy is going to hit it's peak... so once you have the oil changed for the first time, take a little road trip and see what you're getting on the highway.

Our new MCS can JUST break the 30 mpg mark (only 1900 miles on her so far) if I stay on the highway and keep it below 80 (which isn't easy ).

>>Anyway, from what I have seen in the limited amount I get to drive the car, we get about 200 miles in the first half of a tank and around 100 in the second half. Is this common? It seems to me like the half mark is more or less the third left mark... maybe I will find out when I can pump the gas myself to see how much actually goes in, but I'll see....>>

I don't recall EVER seeing a truly linear gas gauge. I grew up driving Chevys and they were the worst ... during the actual first half tank of gas the needle would move from full to 3/4 ... during the next 1/4 tank the needle would move to the halfway point... then it would drop like a stone from 1/2-empty.

I honestly haven't paid too close attention to how linear our's is, however, that's cause I just check the OnBoard Computer for range information, so I honestly don't use the gauge as much anymore (that's true in both the MCS and my Jeep). The range computers usually give me a better idea anyway.

 

Yeah, but in my experience on other cars Gas CPUs is that they will say 0 miles left for like 50 miles if you push it.... They seems to say 0 when you first hit the reserve....

Thanks for the input...
Ben

 

How big did you say the MCS tank was??? like 13.something gallons?

I don't like to run any tank down below a gallon anyway (mostly cause I don't want to risk clogging the pickup filter sock on the pump with whatever junk might work it's way into the tank)... but with that said, I DO ... and my experience with two Jeeps (a GC and a Cherokee) is that when it reads 0 ...I've got about a gallon left via capacity vs what I pump in... and in a Jeep that's NO 50 miles.

Similarly, the MCS (funny side-bar, it's the wife's car, but she didn't fill it up herself until 1900 miles

_________________
She let's me drive her MCS (which is good, cause I gave it to her as a wedding present)!!!

Our Baby? - she's an 03 Elect Blue (white roof/wheels) MCS, w/ all the toys (premium, cold, h/k, Nav, xenon, fogs etc) !

 

I've been driving my MCS around for its first 850 miles and shifting at about 3-4K RPMs. I've been averaging about 20MPG. I am hoping that the gas mileage gets better after I break in my engine. At which point should I shift, if not driving spirited, to get the best mileage? How is the mileage when revving the engine to utilize its full potential at 6,000+ RPMs?

 

>>I've been driving my MCS around for its first 850 miles and shifting at about 3-4K RPMs. I've been averaging about 20MPG. I am hoping that the gas milage gets better after I break in my engine. At which point should I shift, if not driving spirited, to get the best milage? How is the milage when revving the engine to utilize its full potential at 6,000+ RPMs?


It's not just WHERE you're shifting, but how often. The majority of any vehicle's gas consumption occurs during acceleration (running it in the high rpm range)... the engine takes the same amount of gas to spin at 3000 rpm whether you're in first gear going 20 mph (I'm guessing at the mpg/rpm figures so please don't jump on me) or in 6th gear going 70 mph ... but where is your mileage going to be better????

So 20 mpg, I'd guess you're predominantly doing city driving, NOT highway????

Our's is currently getting an avge of about 27 mpg with MOSTLY stop and go city driving. As I said, on the highway I can get it to 30, but I've got to stay below 80 mph.

Of course, your motor is BRAND NEW (and ours is still VERY new), so give it some time. You'll see better fuel economy in a couple months.


_________________
She let's me drive her MCS (which is good, cause I gave it to her as a wedding present)!!!

Our Baby? - she's an 03 Elect Blue (white roof/wheels) MCS, w/ all the toys (premium, cold, h/k, Nav, xenon, fogs etc) !

 

thank you KevM

Most of my driving is city driving. At what rpm range are you driving to get 27 mpg?

 

>>thank you KevM
>>
>>Most of my driving is city driving. At what rpm range are you driving to get 27 mpg?


All over the place, Jenn tends to shift by 4000, I do also, but when I'm in a mood for some more spirited driving (which is once or twice an outing) we're in the 6000 range.

The 27 figure is a mixture of city and highway driving on the last tank or two... including some VERY spirited driving last Sunday

Have FUN!

 

Hehe :smile:

 

>>Yeah, but in my experience on other cars Gas CPUs is that they will say 0 miles left for like 50 miles if you push it.... They seems to say 0 when you first hit the reserve....
>>
>>Thanks for the input...
>>Ben

On the other hand I've spent an hour sitting on the side of a highway in the middle of West Virginia waiting for AAA to come with some gas while my (GM) range computer said I had 44 miles left . So I'd rather get an early warning. Plus you don't want to be sucking up the crap from the bottom of the tank and clogging the filter.

 

>>Who would expect the gas gauge to be wrong.... Must be ford drivers or something....
>>

What, you don't trust that they know what you want more than you do?

Rocketboy_X

 

This is going to sound exceedingly boring and/or rather nerdish as far as explanations go. I have noticed over the years after owning or living with many different kinds of vehicles and working on countless hundreds the gas gauge behavior is different in almost every one. I notice that older cars and trucks have the most predictable gauges. From working on so many cars (many of which involve gas tank removals for fuel pump replacement) it seems to me the correlation of gas gauge 'linearity' to a particular vehicle involves where the level sender in placed in the tank and the shape of the tank itself.

Today's small cars have tanks that resemble human livers and other organs rather than the simple boxes that trucks and older vehicles have. This is done nowadays for space efficiency and utilizing every tiny space available. Because of that, as the tank is filled and the fuel is used, the height of the fuel in the tank can change drastically with a given change in volume depending on where in the tank the fuel is currently.

(waiting for the faces to subside )

Think of it this way: Get a bottle of Coke and open it up. Take a few swigs and see how far down the level is. Take a few more. Since the bottle is tapered at the top it holds less liquid near the top than it does at it's widest part. Since the bottle tapers in again near the bottom the closer you get to the end of your drink the faster the bottle empties with each sip. The same goes for car gas tanks.

There are also differences in where the level sensor arm pivots and how far it has to travel, but that would turn this into a geometry discussion really fast (think how a toilet tank works instead).

Hope this insight helped (and not only as an insomnia cure! )

 

Greatbear.... great point and well said... I'd forgotten how the irregular shapes of today's fuel cells should affect gauges. Thanks! (though, ironically, I still haven't seen a linear gauge and that goes back to my 1970 Olds Rallye 350 and a slew of old Chevy Trucks).

 

Interesting thread, allow me to add some thoughts:

Like many have said, most gauges are not linear, for various reasons. However, there are some additional issues to consider:
theoretically, as your tank empties, your mileage should improve especially in city driving as the car gets lighter. However, many have noted and reported that strangely they get better mileage using the 'upper' 1/2 or 1/4 of a tank, and mileage decreases as you drain the tank. This seems paradoxic, but I have noticed it as well. I have few ideas how this might come about, but recently some interesting thoughts came up: the whole issue of the stumble and hesitation prompetd some to report that this problem may occur only or more frequently with a tank below 1/4 level (and at high temps), and may be related to vapor lock, or to the ECU adjusting in some way to vaporlock. If the ECU adjusts something related to fuel flow and combustion, then this could explain why mileage decreases as the tank empties even though the car lightens.

All that aside, I just completed a 5000+ mile road trip in my 03 MCS, and did quite a bit of experimentation with mileages.
As has been reported, the OBC is way inaccurate!!! You get more realistic mpg values when calculating mileage yourself, BUT there is an inaccuracy related to the fact that when you fill a tank, the pumps may cut off at different times, depending on type of pump, and how it is adjusted, as well as depending on how you car is positioned (leveled). So, the most accurate consumption is obtained when summing mileage and gas consumed over several successive fill-ups.

I also tried to compare the effect of A/C on vs off, windows open vs closed and dsriving style and speed.

On this trip, I consumed 167.3 gallons of fuel over 5139.7 miles for an average consumption of 30.71 mpg for mostly highway driving. Calculating mpg for individual fillups and averaging those I obtained and avg of 30.78 mpg, and a weighted average (by miles driven for each fillup) of 31.21 mpg. The OBC was reset at each fillup, and the values from the OBC averaged to 35.08 mpg, or about 4 mpg more than actual, a greater than 10% difference! What is even more astounding, are the differences between calculated and OBC values for individual fillups, where the greates difference was an indicated 37.3 vs a calculated 29.2, a difference of 8 gallons or a 27.4% !

Highest calculated individual fillup mpg was 38.59, and lowest was 19.49. The former crusing at 70 mph w/o AC and windows closed, the latter during very spirited driving on a very curvy, twisty mountain road. The 38.59 mpg value is probably related to inaccurate fillup value, and does not reflect true consumption.

A/C appears to decrease mpg by about 2-4 mpg, dependent on weather and speed you are travelling at. On average, AC on tends to decrease mileage by about 3mpg during highway driving at about 75 mph.

Windows open but AC off on the other hand only tends to decrease mpg by about 1.5 mpg when crusing at 70 mph, less at lower speeds. Contrary to what I have read in many places, AC does suck up more power (twice as much in terms of mileage change) than opening the windows, and this difference should be more notable at lower speeds!

A very interesting observation is the fact that the cruise control in the MINI decreases mileage. In my view this is because it works so poorly (even after the diode fix): it reacts too slowly and so on moderately hilly roads the car on cruise has an infuriating tendency to DECELERATE on downhills and ACCELERATE on uphills.
In comparing CC vs manual during similar streches of moderately hilly roads, CC use resulted in about 2 - 2.5 mpg lower values than manual gas, a substantial difference.

Finally, the biggest difference is brought about by how you drive. Speed makes a difference, but acceleration more so! If you optimize crusing w/o cruise control, with almost no acceleration/deceleration, AC off and windows closed, you can obtain in excvess of 35 mpg with the MCS while crusing on a highway at 75 mph. At the same time, if you have AC on, cruise control set, but also speed up and break to pass and blend back in, and set CC again, this will easily drop to below 30 mpg for highway 'cruising' at 75 mph average.

 

MG-BGT :smile:

_________________
She let's me drive her MCS (which is good, cause I gave it to her as a wedding present)!!!

Our Baby? - she's an 03 Elect Blue (white roof/wheels) MCS, w/ all the toys (premium, cold, h/k, Nav, xenon, fogs etc) !

 

>>However, many have noted and reported that strangely they get better mileage using the 'upper' 1/2 or 1/4 of a tank, and mileage decreases as you drain the tank. This seems paradoxic, but I have noticed it as well.

Well, since we're being newds here, I'll jump in.

I THOUGHT I could see better MPG numbers when I filled up more frequently,
so I did an experiment. I filled up at 3/4 tank every time, and when I did that, my
MPG gains went away. Boo Hoo.

Anyway, here is 11,000 miles of fuel economy in a 02/02 build MINI Cooper 5-speed:

You can see the experiment at around 8500 miles.