Besides winter grade diesel, how you drive makes a big difference, especially with the turbo. My wife, who would be perfect to drive bowls of goldfish around town, consistantly gets 2+/- more mpg than I do.

By the way, Gil you don't happen to also own a big SUV do you? No offense but you're sounding a little sensitive on that global warming topic. ;)

No SUV (yet)
 

No, I don't have an SUV, but I'd consider getting one, once I have kids.

If I seem a little sensitive, it's just that my BS detector goes off every time I hear the mantra about global warming, etc. Let's face it, even if global warming were a reality AND it were caused by the burning of fossil fuels (I'm still waiting for the actual proof), we'd still have to depend on fossil fuels to get done what we need to do. So yes, the gulit trip about how it's the all our fault is annoying to me, especially when I see it on a government web site.



My 2 cents

Gil

30 mpg is not urban legand or lies. My 1980 240D and 1983 300D both get 30 +/- 1 mpg on the highway, and I frequently push them to 80 mph.

The key to getting my mpg from about 25 to 30 was having the valves adjusted properly, and making sure the injection timing start of delivery timing was correct.

Winter fuel does make a difference but my records show only about 1 to 1.5 mpg less. As I have stated before, I don't believe the mantra about some of the cars just doing better than others. I assume you're talking about the same type of car and similar driving conditions.

I would love to play with one that is getting only 24 or 25 mpg on the highway. I would bet you have something wrong, like the valves, or the timing, or something dragging like brakes or poorly inflated tires, or air filter, or leaking down injector, etc.

I guess what I'm saying is that if you're getting 24 I would do some investigation. Remember, if you get a mpg improvement, you should get a performance improvement also. That's especially important on the 240Ds.

Joe

Is 30 posible with turbo?
 

Hey, I'm happy to hear it's possible to get 30, but is that likely even with a 300 series turbo?

I recently had the vlalves adjusted, but it didn't make much difference. I haven't played with the injection start of delivery, but my guess is that this would help also. Is this hard to do?

Thanks

Gil

30 with the 300d turbo is definitely possible... Valves are key, but as I understand it, they need to be fully cold to be done correctly.
I like to leave my car for a day when I have the stealer do it, as otherwise I dont know if they will let it cool down enough, and might pay for a worthless adjustment.

Just my opinion.

JMH

I'll just say that all the maintanence on my car is up do date and by the books - INCLUDING the valves. Yet, I still only get 23mpg, and no, my car doesn't have any problems like bad brakes, dirty fitlers, etc. According to the fueleconomy.gov site, 23mpg is just right for my '84 300D california model.

I wish I got 30mpg in my car, but I don't. I just want you all to know that low 20's doesn't necessarily mean there is something wrong with the car, and people (especially those shopping for a Mercedes with the 617 engine) need to know that, chances are, they will NOT get near 30mpg in their car.

GregS
'84 300D, 170k

GregS...What is different about your California model? Is there some type of smog control on it? I am assuming that most of the posters on this thread are not driving California models. My 300CD is not a Cal. model. Will this make a diifference in mileage?

Just curious.

mileage - fwiw department
 

last fill (about 1/2 a tankful) i got 23.25 mpg with 90% in-town driving which i consider pretty good for winterized fuel.

Run it on veggie oil and forget the MPG and help the environment at the same time.

http://www.greasel.com/

http://journeytoforever.org/biodiesel_make.html

http://www.greasecar.com/

Tires the cause of poor gas mileage
 

I am so happy that I have switched my Yokohoma Avid H4 P195 70 R14 tires on my 1984 300TD to the Michelin MXV4 P195 70 R14 tires.

You wouldn't think that changing the same size tires from one manufacturer to another would change the gas mileage and acceleration but believe me, it does. My engine runs cooler too now and I don't have a wobbly ride. Now, I am getting much better gas mileage (about 23-24 mph on the MXV4s compared to about 21.5 mph on the Avid H4s) and much better acceleration.

I have seen posts here debating about which tires to buy for the W123 cars. Initially, I had purchased the Yokos Avid H4 because of the price ($52/tire for Avid HR versus $90/tire at America's Tire Center for MXV4). After my purchase, I have never been content with the Avid H4s because of the gas mileage and the wobbly ride, poor acceleration and judging by eye, the tires look larger than the same sized Michelin MXV4 tires and this definitely affects gas mileage. The Avid HR size listed at P195 70R 14 is in fact bigger than the same sized Michelin MXV4s. I have learned to just go with the Michelins as MBZ recommends.

So check your tire size and the manufacturer of the tire to better your fuel economy.

If you search the archives, you will find many threads on this subject. Turbo OM617 mileage varies between 18-32mpg. I personally know folks who do indeed get 30 so it is possible. Mine, sadly, is stuck in the 20-24 range. I have checked EVERYTHING except timing chain stretch (new brake calipers - were sticking, set IP timing, adjusted valves, etc). Performance is great, it does 0-60 in roughly 13-14 seconds, which is about factory spec. My personal gut feeling is that the culprit is the injection pump calibration. I'd be willing to bet a new (or rebuilt) pump, with a good timing chain, would cure the problem. Unfortunately, the R&R procedure for the IP on these engines should be a form of medieval torture, and a rebuilt IP costs a fortune (you could get lucky and get your old one calibrated cheap, if it's not worn out.)

If you live in CA, you will get 10-15% lower MPG than the rest of the USA thanks to CARB oxygenated fuel. Since moving to Idaho I have gotten 10-15% better mileage on all 4 of my diesel vehicles, as long as I use non-CA fuel (tried NV, ID, OR, and WA so far.) The winter blend will cause a 3-10% drop in economy though, so don't forget to allow for the between October-April.

Last note: Tires should NOT make a big difference in MPG, as long as they are the same size, run at similar pressures. I have heard of severly bad alignment causing poor MPG, though. My car needs some front end work - and an alignment - so I'll see if that cures it. I happen to have Avid H4's on it now, but the MPG was the same with the Pirellis they replaced. I would not recommend new tires in hopes of magially increasing your MPG. Check the other basic items first (search the archives, we've beaten this to death many times already...!)


Regards,

Tires DO make a difference in MPG
 

With respect to the post by Gsxr, I was (past tense) of the opinion that tires should NOT make a big difference in MPG, as long as they are the same size, run at similar pressures. This was what I had thought till I purchased tires from different manufacturers of the same listed size.

Having owed both the Yokohoma Avid H4s and the Michelin MXV4, I am in the unique position to comment on both of these high performers. Like most people, I too, am of the opinion that tire sizes should not make a big difference in mpg as long as they are the same size and ran at similar pressures. The strange thing is, the Avid H4 at P195 70R14 is a slightly physically larger tire than the same sized Michelin MXV4. It has to be, the H4s are advertised as high performance tires. If you don't believe it, go to your tire store and compare these two tires for yourself and I'm confident you'll come to the same conclusion as I have: that tires from different manufacturers, although at the same size, do affect fuel economy. It is no mystery that Mercedes Benz of Stuggart, Germany officially recommends the Michelins.

Tires! forgot about that bit!
 

Oh, hell, I completely forgot to consider tires.

Right now, I'm running Bridgestone 205 70 R14s. They're slightly wider than the stock 195 size, so yes, the increased surface area would definitely be noticable on highway gas mileage, if not around town for short trips.

Still, the Bridgestones are a far superior tire to the Coopers I had on before. They were gone in less than 24K miles. The fatter size helps a bit with handling, particularly on exit ramps, so I can accept the trade off, I guess.

One other thing is the alignment on the car, which I seem to have to have done annually. It's always much better for tire wear and potentially economy to have this done regularly.

Still, I'd like to know how often everyone out there has there 300d/CD/SDL aligned. Seems like these cars need this done more often than most. I've been told that's just the result of the design.
Is this true?

Thanks to all again,

Gil

300Ds are vastly different, so expect different mileage from different mills. I'm lucky. My '91 OM602 five banger consistently gets over 30 mpg on the highway, and performs exactly according to its 27 city, 33 highway rating.

Then again, I also have a rebuilt injection pump.

BTW, Calif. fuel may be oxygenated, but it's also the best in the nation, with nearly 50 cetane. I never worry about bad fuel, and do not bother with additives.

My Dunlops are getting thin, so next week I'll probably slap some Continental Touring Contacs rated by CU for good handling and low rolling resistence on the car. About $70 apiece (vs. the Michelin Energy's $125 OUCH!!).

OK, I guess I should clarify. I can believe a 1-2mpg difference between tire brands or types. But you will NEVER turn a 22mpg pig into a 30mpg princess by changing (similar size) tires.

On a different note, I highly discourage putting on larger/wider tires than stock. Using a 205 in place of the 195 will make the speedometer more inaccurate than it already is (you can check it with a GPS). And, more importantly, the wider tire will "swim" around the narrow rim. You gain a little bit of straight-line traction and that's it. Handling actually worsens due to sidewall flex. Any perceived increase in cornering power is, IMO, either due to a better tire compound than your old rubber or simply the placebo effect ("it's wider, so it MUST work better!").

Stick with the OE tire size... if you must go larger, get a WIDER WHEEL and use the proper size tire for that wheel. MB sizes tire+wheel combos on their newer cars very well, with 205/55/16 on a 7.0, 215/55/16 on a 7.5, and 235/45/17 on a 8.0 (for the 202, 203, 208, and 210 chassis). These all swap on to 124's easily. The 123 guys have it a little tougher. :) The 123 is not exactly an autocross rocket so I just keep the stock alloys & tire size on that car.

On a side note, both my 124's with the OM603 get MUCH better MPG than my 123. The 124's are about 26/32 city/highway on summer fuel, while my 123 is more like 22/24 (has never exceed 24mpg in the last 15kmi).


:p


Regards,