mis3

I rent a Chevy Cruze this weekend to go to Montreal (from Toronto). The distance was about 350 miles one way.

In the first trip, I set my cruise to 75 mph and my mileage was 34 mpg. In the return trip, I did 63 mph and the mileage was over 39 mpg. This is more than 10% saving. I know there were certainly other factors, it looks to me that 60-65 mph is a sweet spot for the Cruze engine for gas mileage.

Is there any such sweet spot for our engines?

Rudeney

In the CLK, a lot will depend upon the engine and transmission. For example, my CLK550 turns just over 2000 in 7th gear at 80mph, which gives me about my best efficiency (25mpg) at highway speeds. Running around town in light traffic on 45mph secondary roads, the transmission is in 6th and about 1500rpm, and I get right at 20MPG.

mis3

My current combined mileage (2004 CLK320) is about 23 MPG. I recalled for these Toronto-Montreal trips with my MB, I would get almost 30 MPG if I set the cruise to 63-65 MPH.

I started to look at my gas mileage recently when it dropped to about 20-21 MPG. The I found out the my tire pressures were all low (5 PSI low for my fronts).

I probably should change my driving habits. I am way too agressive with my gas pedal especially in city driving. Too much fun but I am not getting to my destinations any much sooner!

I read that dirty MAF would impact gas mileage as well. I will look into this. Too bad my indie was reluctant to clean the MAF, he was concerned that some old clips might break when removing the MAF.

Rudeney

Your mechanic is right 0 that plastic "handshake" clip holding the M112 engine's MAF sensor almost always breaks when you try to remove it. But it's a cheap part. Also, the gaskets on the MAF sensor are often bad, but again, another air of inexpensive parts. It's probably worth the price of those parts to try to clean the MAF.

mis3

Are there part numbers to this clip and gaskets?
This is one thing that dealerships are better because they would have these spare parts in stock.

I also read that some members here clean their MAF without removing it.

Rudeney

#7 and #9 here:

http://www.parts.com/parts/2004/Merc...iagram=5775181

You can try taking this to your dealer parts counter and get them to price match.

labguy

On my daily commute in my 2008 CLK350 Coupe , I have been averaging 27-28 mpg. (I have a light right foot). Most of the drive is on State Highways with a 55mph limit. At 55 mph in 7th the engine is doing 1600 rpms.

mis3

Labguy: Great mileage. It sure makes a big difference with a light foot.

Rudeney: Is MAF sensor a consumable item; ie: its performance deteriorate over time? Mine was changed in May-2008. So this MAF sensor has been in use for 105K miles and over 5 years. Not sure if I should change it or just clean it. The car drives great, just low in gas mileage.

betrezra

My kleemann supercharged clk55 got 24mpg at 65mph cruise on the way to work today..... if I drive like normal.... it is 17mpg

Rudeney

I would consider a MAF sensor, like an O2 sensor or a catalytic converter, to be a "consumable". It does eventually wear out and need replacement.

mis3

Just curious. I checked a Canadian online store and searched by part number, 1120940048. They sell the Bosch MAF Sensor for $180CAN but the description did not say if it is OE or OEM. Part no. listed was BOS1600866.

http://www.autopartsway.ca/search.cf...rch:1120940048

I then did the same on Autohausaz and it returned a Bosch MAF sensor. Not much description there and it did mention OEM for $145US. Part no. on the site was Bosch 0280217515.

By the pictures, they look the same. My question is does Bosch make only one MAF sensor for w209? If I decide to get one later, I would perfer to get it from a Canadian store.

Rudeney

I believe there is only one Bosch part for that engine. Just avoid the cheap eBay Chinese MAF sensors. They are crap.

mis3

OK. Thanks.

My MAF sensor is over 6 years old so it may fail soon. I rememeber last time when it failed, they were signs (the car hesitated) and the car was still drivable. I should probably wait for these signs and then change it.

BTW. It was changed by the dealership under warranty. Good that I did not pay, the list price of this MAF sensor was $450CAN at the time. Wow.

Rudeney

I would not change it unless you are having specific problems (like you did before). Another symptom is high fuel consumption. I would also, try cleaning before replacing.

clydem

If you want better fuel mileage, there's all sorts of forums on tips & tricks. It's really all about your driving habbits & techniques. IMHO - you bought a benz for comfort, not a smartcar for mileage.

That being said: If you run a vacuum guage off the manifold, you can improve your performance. Or, check out a SCANGUAGE II. Buy one from Autozone when they have coupons & discounts & you can get it for $50. It connects to the OBDII connection. It can teach you to drive efficiently as can your dash MPG gauge

In general, I find 40mph to be the highest vacuum and best fuel mileage for automatics. That's impractical. So no jack-rabbit starts and cruise control is your friend. Even at 25mph. Spirited driving is not Fuel Economy's friend.

labguy

I find that when I set my CC to 55 mph the transmission will sometimes stay in 6th at 18oo rpms. When I notice that, I give it a little throttle, then ease off. When I do that, it goes into 7th at 1600 rpms.

I also like to disengage the CC when approaching a red light and coast up there instead of going from throttle directly to brake.

Rudeney

My CLK550 won't shift into 7th gear until I reach about 52mph, and then I have to use the TouchShift to "nudge" it to upshift.

mis3

The local highway speed limit is 60 MPH.

I usually set my cruise to 75 MPH and at this speed, the RPM is at 2800. Unfortunately, this is probably not the best speed for fuel economy. Maybe I should drop it to 68-70 MPH, because most of the time, a few MPH less does not reduce the commute time noticeably.

mis3

I am sure my local dealerships would not do price match. They would claim they are not the same items because most parts in the dealership are MB-packaged.

I did go to the dealership to ask for these parts; mass air flow bracket (#7), top housing gasket (#9) and bottom housing bracket (#10). They are a few dollars each and unfortunately, they did not have them in stock. I told the parts guy that I planned to clean the MAF sensor, he then tried for 10 minutes to talk me out of it. He insisted that MAF sensor should be replaced, not cleaned.

Glyn M Ruck

He's trying to sell parts. Try cleaning the MAF first.

Rudeney

What engine/transmission is that? (update your forum profile and I'd know! ) My CLK550 with the 722.9 is turning just over 2K RPM at 80 MPH, and that seems to be the sweet-spot.

Rudeney

FYI, parts.com is just a consolidator - the parts are genuine MBZ shipped from participating dealers. Your parts guy is giving you the official company line - MBZ does not recommend cleaning the MAF sensor - they only have instructions for replacement, and only after verifying that the live data read via SDS confirms that it's bad.

mis3

2004 CLK320 Coupe; so M112/722.6
At 120 KMH (74.5 MPH), RPM -> 2800
At 100 KMH (62 MPH), RPM -> 2300
At 90 KMH (55 MPH), RPM -> 2100

As for the MAF sensor, I looked at the diagram for my specific car in parts.com. http://www.parts.com/parts/2004/Merc...gramCallOut=10. This CLK320 diagram is a bit different than the one for C320, strange since both engines should be the same.
In the diagram of CLK320, I see #7 as the Air Mass Sensor Gasket which is the only item which sits on top of the MAF housing.
In the diagram of C320, I see 2 items sitting on top of the MAF housing; Air Mass Flow Gasket and Housing Gasket (#7 and #9).

I can see the 2 clips of the Air Mass Flow gasket in the C320 diagram but not in the CLK320.
I read that these 2 clips can be broken easily when removing the MAF so this is a must-have part, just in case. This bracket is probbaly 10-year old, not sure if they replaced it last time they changed my MAF 5.5 years ago. How about the other 2 housing gaskets (#7 and #9 in the C320 diagram)?

Rudeney

The parts.com diagrams are too generic. These from EPC should help:

http://benzbits.com/m112/AirIntakePartsDiagram.pdf
http://benzbits.com/m112/AirIntakePartsList.pdf

mecca281

Interesting thread. I have a 2006 clk350 My mpg has been averaging at about 20. I've cleaned my MAF about 5 times now and it has never been replaced. I get a lot of hesitation, and I do notice a difference when I clean the MAF, but now the hesitation just seems to stick around.

Question, when is it time to change the MAF and not just clean it?