How fast are you traveling on the highway when you are getting GREAT mileage ?? - PeachParts Mercedes-Benz Forum

kamil · #1 05-13-2004, 09:02 AM

Just wondering.....

thanks

schooner · #2 05-13-2004, 09:29 AM

i get my best mileage at about 50 mph and that would be about 35 miles per gallon. Unfortunately I rarely drive at this speed.

Rick Miley · #3 05-13-2004, 09:59 AM

Your 83 240D was designed with the sweet spot at 55 mph. That was the national speed limit back then.

janko · #4 05-13-2004, 10:04 AM

interesting. recently received a well deserved speeding ticket. subsequent change in driving habits, read that 55 to 60mph where warranted, has resulted in my fuel efficiency going from around 27-28 mpg to the low thirties. mostly 31 - 33 mpg. all this in a a manual transmission 240d, 83 vintage.

djugurba · #5 05-13-2004, 10:07 AM

you got a speeding ticket in a 240D? I got pulled over in my old volvo 240 wagon once, and the cop and I agreed that it could not have been me, the car wouldn't go that fast.

janko · #6 05-13-2004, 10:12 AM

received the ticket while in my 86 300sdl. i was very fortunate. exceed the limit by easy 20+ mph. the good officer recorded my misdeed as 17mph over. i am generally not that fortunate. and the 240 will go close to 90mph. takes a while to get to this speed. but it has been done numerous times. before the speeding ticket of course.

Chris Blanchard · #7 05-13-2004, 10:23 AM

How fast did he say you were going in your 240 wagon? I've owned two of those (89 w/ 5-speed, and a 93 w/ auto) and I don't think those could break 85mph even with a tailwind.
I think the best gas mileage I got out of either of those gassers as about 25-26 on the highway, and I'm usually travelling only 5 or so mph above the limit (much less stressful than driving fast and having to be on the lookout for the cops).

As for my MB diesel (92 300D 2.5 turbo, 163k miles), I find that my normal highway driving gets me about 33-35 mpg on summer fuel, mayble 1-2 mpg less on the winter fuel.

I just love the fact that my car gets that kind of mileage. My old W126 300SD never would get better than 24-25mpg on the freeway. My old W123 300D did about the same.

So, with diesel here at $1.64/gal and premium at $2.05+, I'm saving a boatload of $ by driving this 300D as opposed to my 94 E420 which gets 22?mpg on premium. (The 94 is for sale by the way - not due to fuel consumption, rather I bought it from my brother-in-law with the idea of selling it to make a little money that I can use to fix a few items on the 300D: a/c, front susp.).

I'm really hooked on my W124 300D 2.5. It's quiet, comfortable, gets great fuel mileage, plenty of room under the hood (compared to the OM603 in the 87s - block is 4" shorter).

I don't see many cars like mine on the road, but I love mine and would buy another in a heartbeat if this one got totalled out.
Color combo is nice also: Pearl Black over Creme Beige Tex.

Combine that with a low purchase price $7k, and reasonable maintenance/repair bills (I mostly DIY) and this car is a winner in every sense. Low/no depreciation, safety, stylish, sufficient power, cost of operation is reasonable. I can't see buying a new car even if I had the money.

Chris Blanchard
1992 300D 2.5 Turbo 163k miles (maybe will re-badge as 250D).

84300DT · #8 05-13-2004, 10:27 AM

seems to be 80mph these days

Grdenko · #9 05-13-2004, 10:55 AM

Chris,
ditto on the 300D 2.5 turbo
this car is the greatest, i consistently get 30 mpg on the highway at 85 mph. ive got silver/burgundy. my dad gives me an offer on it every time he sees it, but im going to keep it for the rest of my life.

Jim Anderson · #10 05-13-2004, 11:03 AM

I remember a long time ago there was a car mag that had a chart that plotted speed and mpg and they all peaked at about 45mph.

cornblatt · #11 05-13-2004, 12:59 PM

In the German owner's manual for a 1986 european-model Mercedes I looked at last year, there was a nice graph near the back that plotted speed vs fuel consumption (in liters per 100km). There were three different lines on the graph; one was for the 4-speed manual, one for the 5-speed manual, and one for the automatic transmission. I was surprised to see that, according to the graphs, there wasn't a particular optimal operating speed; fuel consumption just seemed to generally increase with speed. The plot was almost exponential - quite flat below 50km/h, quite steep above 110km/h, and curved in between... There was also some text beside the graph offering details in German that I couldn't understand.

I wish I'd taken a photo of that page... does anyone here with a European model car have this in their owner's manual?

Another way to answer the question about optimal speed for best fuel economy is with something like this diesel consumption meter:
Picture -->

PDF File --> http://www2.vdo.com/vdo/sycomax/files/503849_EDM1404_gb.pdf
Does anyone know where to get one?

Veloce300DT · #12 05-13-2004, 02:10 PM

Seems like I get the best MPG around 80MPH. I frequently drive from San Francisco to Sacramento (about 85miles i think) , usually at a steady 80-85MPH and the fuel gauge needle only moves to the first line from a full tank at the most.

Veloce300DT · #13 05-13-2004, 02:14 PM

I also use Redline 85+ diesel fuel catalyst. Not sure if that makes a huge difference in MPG but it certainly runs smoother since I started using it and I have extremely minimal black soot expellage from exhaust.

I actually ran the car at about 102MPH for a good 10 minutes on a desolate smooth highway in the valley- for a minute or so a continuous plume of soot flew out the exhaust, and then quickly minimalized. The soot has been virtually non existant to the eye ever since at all speeds and rates of accelertaion.

BoostnBenz · #14 05-13-2004, 03:58 PM

Well the speed that I get the best mileage isn't very good for highway driving. I normally fill up with diesel until it almost spills out (normally the foam isn't much of a problem), well I filled up before then drove at around 55 for 20 miles then 15 miles at 40-45mph (stopped probably a dozen times in all). When I got home I tried to drain in the 4qts of motor oil from a recent oil change but not all of it would fit! When I get upto the mid 60s my mileage seems to fall down a little bit more but at one point in time I was getting a consistent 31-33 on winter fuel, lately it has been in the 28-31 range due to all of the construction and driving it a little harder (also thinking it is about time for new nozzles). Anyway I believe if I drove a steady 45mph I'd get 40s or 50s in mpg but since that isn't feasible....

WannaWagon · #15 05-13-2004, 08:12 PM

Quote:

Originally posted by Veloce300DT
Seems like I get the best MPG around 80MPH. I frequently drive from San Francisco to Sacramento (about 85miles i think) , usually at a steady 80-85MPH and the fuel gauge needle only moves to the first line from a full tank at the most.

So, what kind of mileage DO you get?

Cornblatt: That gauge looks like an industrial unit intended for big diesel trucks. I'd suggest a trucking supply or parts store. One big outfit that sells a lot of VDO gauges is www.egauges.com, so you could try them, too. You could also try a local speedometer repair or gauge shop. Look in your phone book under "speedometer" or "gauges."