maintaining my car since new, Ive averaged around 22-24.5 mpg city(sometimes I can even hit 29) and between 27-34 highway.

 

at 70-75 I get like 31-35mpg all day. Mostly depends on weather (I live in high wind area). I do however find myself driving pretty zippy around town, getting 19-23 mpg is pseudo-normal for me. I have probably 5+ pictures of my dash listing a mpg of 35+mpg over 20+ miles on freeway. I noticed putting crappy ethanol 92 octane dropped me down in the 28-30mpg range though. And yes that crappy ethanol gas was from a Chevron! Seriously guys i wouldn't put that $h*t in my lawnmower, know why??? because it says in the lawnmowers owners manual that it will "RUIN THE MOTOR!". If u are not lucky enough to live in a po-dunk farming town like me and don't have access to non ethanol 92, then u should be techron-ing monthly. good popcorn although makes for great farts, is not a viable solution for powering high performance engines... sorry for the rant.

In summary, m271 230s should see 30+mpg NO PROBLEM on the freeway, and if your not, u gotta problem somewhere. Barring obvious tire issues, I would start with your fuel, then techron, then change your air filter, then plugs, then if your not running in the 30s I'd sell that **** before your stuck holding the lemon. Take the $ and buy another benz and rest easy.

btw it seems like you might be confused about taking your mileage properly so - if your not understanding how to take your mileage this is how: if you want to find out freeway mileage, get up to your desired cruising speed(65mph-75mph), set the CC, then reset your mileage, it will start up around 28mpg and climb or drop from there. City mileage is shotty at best and is not a good indicator of how your engine is doing because unless its below 15mpg, it could totally depend on driving style, how many hills/stopsigns/school busses/u name it happens to be in your city.

 

Since this is mainly my beater, I haven't spent any time under the hood other than wiring my HIDs. Is the air filter and plugs an easy change? I've worked on plenty of other cars as it is my hobby, but didn't want to bother with this one.

 

anybody with 2.5 V6 get more then 25mpg highway?

 

I get 31 mpg if I go all highway. But I just got new rims and tires so itihht change a bit.

 

I have done the air-filter, plugs, techron (however I NEVER had the problem with MPG that you have currently, although I did find a noticeable improvement in performance doing the above). They are all very easy. To do all of them would take an hour or so for most semi-mechanically inclined DIYers. There are good step by step instructions complete with pictures for the plugs and filter (don't get caught up in the K&N vs. factory Bosche non-sense, just pick your poison and live or die by it - I go with factory Bosche and get 31-35 MPG and have all the performance I need). I would say you could add cleaning and inspect of the MAF sensor and intake tubing (some members have posted that they have found intake tubing/housings clogged up with a rats nest of undesirable debris), which there also is good step-by-step instructions in threads here (I think it takes an hour or so, good idea to do it along with the plugs and filter). Also the fuel filter would be a good idea, think theres DIY on here for that too.

I would also recommend the $12 hose replacement, which requires a little more effort, might be a good idea just to have MB run your VIN to see if it has already been done, cuz if it hasnt they will do it for free (which is always the best price). If it has been done, there is some evidence from forum members that after 25-50k miles it needed to be done again, which was done on their dime... which is literally $12 and 2 hours of time (granted you have girl like or "Asain-like" hands - not my quote) - with this problem usually you would notice that your car is running rougher than normal, especially at idle, but since you bought it this way, it would likely seem "normal" to you.

Doing all of the above will cost you in the neighborhood of $150ish. I stand by my previous statement though, IMHO if you do the above and don't get above 30mpg reliably on the highway, sell that **** cuz something is going on that is gonna cost you alot of time and/or money to figure out and square away.

I would say that you will find on here that although these are MB's, they are quite easy for the at home pseudo-mechanic to do most routine maintenence on. This forum provides good knowledge base to do even harder items such as AC compressor/pulley replacement and more complex suspension tweaking. Most of the time all you need is some decent metric socket set, torx set, tweakers, elbow grease, and a fridge stocked with the beer of your choosing

 

[quote=splinter;4553678]Never known you to drive like a dorkmeister. How does your stout M111 consume less fuel than a pantywaist M271?
My 16-gallon tank barely goes 250 miles with the Mrs. lollygagging around town. Almost certain she seldom goes past half throttle. [=quote]

Good job M271 guys for not biting on this attack and ruining the legitimacy of this thread...lol

 

This was done in the past year. I called one of the dealerships by me to check if it has been done.

 

Well, you got some good ideas here, hopefully you figure it out. Once you get them running right its actually a really nice alternative to a honda, and still quite reliable when you take into account the comfort and "fun to drive" aspect (some sacrifice has to be made). I too replaced a honda with the W203 1.8 and have been very happy with my decision, even though I have spent a little more money on her. I am at least 1.5 hours away from either a dealership or a good indy. Once you get her going, do the Aux input (or does yours already have that?), its well worth the $50 for the part and 30 minutes of time installing it. Plus the satisfaction of knowing u did for $50 what MB would charge you $500+ for is priceless. Makes you forget about the $300+ you will spend on a B service when the time comes...

 

Seems to be a wide range of gas mileages in this thread. Keep in mind the differences can easily be accounted for in:

1) engine displacement
2) Manual vs Auto transmission
3) use of air conditioning
4) driving style.
5) trip computer reset habits
6) tire choice

and that comparisons should take all these into account.

I notice those of you getting 31-35 mpg mostly have manual transmissions. Higher mileage with a manual is to be expected.

Resetting your trip computer when you are up to highway speeds is a mild form of cheating, IMO. I measure mileage from tank start to tank end, and let the chips fall where they may. My average speed per tank is usually 38mph (includes city and hwy driving).

You will find that using the climate control system full time lessens your gas mileage. I run my C320 3.2L V6 auto in the "Rest" a/c setting on all but the hottest days. It's just that pleasant in Dallas year-round... open the RR window 3 inches and tip up the sunroof and you have nice air circulation at any speed. From experience over 10-years, I can tell you that using the A/C fulltime depletes at least 2 mpg (32-50 miles) from any tank avg.

Finally, I changed from the standard 205 width tires to 225s, and noticed mileage drop over 30K miles. The fatter tires look cooler, but that extra 1/2" of rubber contact created more rolling resistance for me. Once I went back to 205s, the mileage returned.

YMMV.

 

i have over twice that size and get that mileage on the highway

 

A picture is worth a thousand words...

Here's some proof... C320, 3.2L V6, automatic. A/C at "rest."

Left picture is normal, 10-11 hours of driving over a typical 2 weeks here in Dallas. Tank full to almost empty, 12 starts from cold, stops, idling at lights, everything in between. The higher your average speed (LL) the better the overall mileage = 26.2mpg. 424 miles on the 16.4gal tank (it actually holds 16.8)

Right picture is a 3 hour Interstate commute from my home in Dallas area to my job in Round Rock, TX in 2007. Notice the ambient temperature. 32.1mpg

 

rememeber guys to reset the mpg while you are driving. I dunno why but my car will get terrible mpg and then when I reset it get above 25 all day in the city

 

32 mpg seems really good for a C320, congrats man thats awesome. I still think regardless of conditions, a 1.8L 230 should be getting over 30mpg easy on the freeway. I could never trust a start to finish on the tank just because I hardly ever drive freeway miles. I live in a 14000 population city with about 20 stop signs between my house and work. Plus I'm usually driving pretty zippy in town because I went to HS with all the cops...
After buying this car I have made mpg calculation into a fine science, mostly because my brother is the GM of the local Honda/Toyota dealer and is pissed at me for buy a MB (even though i let him do the financing on it...). So when he says "dude, why didn't u buy that Accord?" I can say "dude, i get better gas mileage in the MB, and its waaaaaay more fun to drive!" - then I show him one of the 20 pictures I have of my dash showing 33-36mpg at 65-75mph on a trip to the city.

 

Fellas, the Mercedes-Benz trip computer is programmed to calculate "since start" mileage from a cold start (more than 4 hours since last start) to any point in time while you are driving, to when you stop at your destination. Obviously, this takes into account all events in your drive.

If you reset the trip computer once up to speed on the highway, you are cheating the computer into delivering "instantaneous" mileage, instead... an average mpg since the reset, only. You are instructing the computer to ignore warm-up from cold, any stops for lights, or acceleration to hwy speed. IMO, your claims of 34-35mpg are quite misleading, when compared to others who use the trip computer as intended.

Ocassionally, I have done this myself, just to see what the computer does, and indeed it gives very inflated mpg calculations. (Reset while coasting down a hill to see 45-50mpg, no problem.) However, you're just teasing yourselves. Manually calculating miles driven / gallons used on fill-up will bring you back to reality that can't be fudged.

I use the "Since Reset" page to compute tank average from fillup to fillup, and I use the "Since Start" page to compute daily commutes. I believe all c-class models have similar pages, although they may be named differently.

 

The best way to measure your gas mileage is just reset the miles every time you fill up your tank, and then divide the number of miles by the number of gallons it takes to fill your tank up after the drive.

You should be filling up to about the same level every time, because if you just let the pump go until it cuts off(which you should because you shouldn't overfill the tank) it'll cut off at the same level each time.

This will be the most accurate way to determine your mileage average.

 

Yeah, that is the best way, but its a hassle sometimes. Stopping multiple times in a day for gas just double check what the car already does, plus since I live in Oregon and am not qualified to pump my own gas (go ahead and chuckle guys, and No, the gas jockeys rarely ever wash the friggin windshield unless its out of spite), I have to be a **** about telling the "Gas Attendent" to make sure not to top it off, or to top it off depending on what the first jockey did. I do check it every so often and usually find that the car is 1-3mpg of what the math says. Good advice though

 

wow, I'm pretty impressed by you guys, especially Bob!

in the C230 (which is getting REALLY close to 100k miles), with only Chevron 91 in it with Techron Concentrate Plus added to it about twice a year, a fuel filter that was replaced at about 70k miles, 19" wheels with 235's up front and 265's in the rear, I generally get 16mpg in pure city driving. Combined city and highway, with me trying to get good gas mileage, I get about 25-27mpg (both statistics were from the on screen display).

During long trips, I can get about 400 miles on one tank.

The M5 on the other hand:

 

Here is how I track for all my cars...
The entry with 13.76 mpg is with my wife warming up the car in the morning for 15 minutes and driving very very short trips (1 mile each trip).

This is my mileage for '07 C280 4-matic with ABSOLUTELY nothing wrong with the car, tires properly inflated, no jack-rabbit driving. Mixed city/highway driving.

I get very similar (slightly lower) mileage on my '04 C320 4-matic as well.

 

Bob's tips are spot on. Also remember that wider tyres mess up the aerodynamic cd of the car as well as rolling resistance issues. By more than you might think.

The W203 achieved it's .27 cd with 195/60/15 tyres fitted.

 

I got down to 6.7L/100kms one day traveling from St Louis to Albuquerque. That includes the initial cold start and stops for gas/food.

My regular city driving is 12.2L/100km, and on trips from Vancouver to Seattle I can get into the ~7.5L/100km.

Thus I agree with others, if you're getting good mileage on the highway then your bad mileage is just cause of the type of city driving you do. I have a very bad commute of start-stops, and a lead foot, so my mileage sucks.

 

Wow, 6 mpg on the M5, lol, that's pretty bad man.

I have a lead foot and even if I gun it all day, I can't get lower than 20-21 mpg with the 2.5L V6. Unless of course I'm sitting on the beltway for hours in traffic, which is why I'm glad I take the metro to work!

 

 

That translates to 5.15 gallons for 100 miles. That translates to 19.41 mpg. That's not bad for city driving.

 

Yeah I know you know how bad the beltway is lol