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-   -   Increasing L/100km??? (http://www.maxbimmer.com/forums/showthread.php?t=152478)

nzibbs 08-06-2012 10:27 AM

Increasing L/100km???
 
Hi there,
wondering if anyone has had a similar problem or has any mechanical advice, ie. should I go into dealer for service check...

I just bought (1.5months) a pre-owned 2010 328i x-drive.
When I picked it up, reading on L/100 km was at 11.1.
Since then, its slowly creeped up to 12.7. I know this is related to driving style, which is what perplexes me. I may have driven somewhat more aggressively in the first week or two, but since then, have been driving very normally, not aggresive at all in driving style etc... so why does it keep increasing by 0.1 every 2-3 days?.... Anyone have any insight to offer?

Cheers,
NZibbd

Smitty 08-06-2012 11:34 AM

Are you referring to an overall average? A per-tank average?

nzibbs 08-06-2012 11:39 AM

Sort of, its a reading on the digital dash, but it is an average and of course as a result i am getting fewer and fewer kms for each full tank...

SiR 08-06-2012 11:41 PM

why not do a manual calc over a few tanks and see where you sit?

blakneto 08-07-2012 02:48 AM

I would go by $$$ per full tank. Use the meter to warn you when you are driving bad.
It doesnt take much... Driving fast doesnt give you a high number, hitting the gas hard and breaking hard does. Auto or Manual?

Smitty 08-07-2012 08:26 AM

Tell us about your commuting patterns.

sproule905 08-07-2012 09:05 AM

my M5 gets on average 12.2L/10km. although back roads to the cottage in 6th gear for me 8.9L

Blades 08-07-2012 09:29 AM

I would say thats some pretty crappy mileage.

Did you change your spark plugs recently? Is your air filter clean?

MrRWD 08-07-2012 11:42 AM

1 Attachment(s)
There are many factors.... AWD, outside temperature (AC Running), 100% Highway, 100% City, combined (what % of each ).

It's been hot, perhaps you're running the AC more.

You should benchmark the car and limit the variables.

When I can, I benchmark the car as follows
- Fill up the car near the highway.
- Drive approx 150KM on the highway to my location
- Approx 110km/h
- Straight driving, no stop and go - (evenings)
- Fill up again & calucate L/100km.
- If I reset the dash L/100km, it's fairly accurate to the actual. This has been true for my E46 and E90/E92's
- I do that trip 1-2 times a month, so it's easy to keep it in check.

blakneto 08-07-2012 12:42 PM

Does AC really eat that much up?
I never quite understood or believed that...

nab24- 08-07-2012 12:51 PM

AC doesn't change it that much but yes, when you turn on your AC it engages the clutch on the compressor there for the motor has to work harder to power the AC compressor. However turning it off and rolling down the windows won't increase your fuel mileage on a hot day because then your just taking away from the aerodynamics of the car. Sooo it's not a bit deal. But yea if it's getting worse and you're not changing your driving habits it could need a tune up.

InfiniteDice 08-07-2012 03:13 PM

Rolling the windows down in the city does nothing. Cruising on the highway it will have an impact.

As blades mentioned... perhaps change your air filter.

EMPOWERD 08-07-2012 06:52 PM

When you picked up the car, it may have had more highway mileage from previous driver/owner which alters the avg consumption. Plus the possibility it was driven without the A/C running. I noticed I get better mileage using 91 oct vs. 87 oct gas (a wash considering the price difference).

MrRWD 08-08-2012 12:24 PM

Remember when the EPA changed the rating systems, and manufacturers had to re-calculate their values... in 2008/2009.

The use of A/C was one of those few changes. They added testing in hotter outside temperatures (95F) - simulated using a dyno most likely.

The easiest to measure is highway mpg.
Get on the highway at the east or west end of the city. Fill up just before (use 91-94).
Reset your trip and drive 20mins at about 100km/h-115km/h constant.
Fill up right away, and manually calculate as well...

- Enjoy the drive... benchmark your car

5style 08-15-2012 04:17 PM

Well, here is what I did recently.

-brand new vacuum hoses, ALL OF THEM.
-Belt tensioner
-Belt
-Valve cover gasket
-manifold boot
-ICV cleaning
-PCV cleaning
-O2

Results: Much smoother, no surging, and about 220km to $20.


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