83 300D Turbo MPG???? - PeachParts Mercedes-Benz Forum

Billybob · #1 02-05-2002, 12:37 AM

Assuming every thing is right and tight what should one expect to get for average mileage for this 5-cylinder? Assume a 60/40 highway/city mix. I'm looking into buying this car for my 17 year old daughter and was wondering what the average driver could expect?

The reason I wonder is that in driving the last 1500 miles in my 87 SDL I've averaged 30 -31 MPG using 7oz. of Power Service per 20 gal. tank of fuel. This mileage is amazing to me as it easily beats my 4 Cyl. 92 Izuzu PU by 5 MPG. Could I expect a 16.7% increase in a car with one less cylinder? The 617 is 2.5 liters as opposed to my 603 3.0 liter right? Any experiences and opinion are welcome. Thanks all.

DieselHead · #2 02-05-2002, 11:06 AM

I get 23-25 mpg in 80/20 town/highway driving. This is in Westchester NY with a car that has its turbo turned up and therefore the ALDA adjusted to provide a bit more fuel. Also, the valves haven't been adjusted in many many many miles (50K atleast......... yes yes, I know, heresy, I'll be doing it ASAP).

Alex

gsxr · #3 02-05-2002, 11:36 AM

The OM603 engine is actually more efficient than the OM617, so no, you won't see an increase in MPG. They might be about equal, although it seems the OM617 tends to get slightly lower MPG unless you drive very conservatively.

The OM603 appears to have almost no MPG penalty at higher speeds, the best MPG I ever got on mine was 30-31, and that was at a steady 80-95 MPH in Idaho & Montana. My normal highway mileage (70-80mph) was more like 28. Weird. Also, the W126/W124 cars with OM603's usually have taller rear ends, due to the extra power availble.

For all OM617 & OM603's, don't expect more than upper 20's or low 30's at BEST. If you want more, you need to get a 190D with a 5-speed, these routinely get 30+, can be coaxed up to nearly 40mpg!! The 84-85 4-cylinder models get better MPG but the power is kind of weak compared to the 86-up 5-cylinder.

HTH,

BWatson · #4 02-05-2002, 02:25 PM

I can't seem to get my car over 22 mpg. It runs perfectly, has lots of zip, minimal smoke, and hardly burns a drop of oil. It starts right up in the morning and is well maintained. I have been using Red Line catalyst to get this improvement because it was only getting about 18 mpg before. I read in this forum of people getting over 25 mpg and I want to know if this is possible. I don't have a real heavy foot but I do like to zip around. Any input would be nice as I have searched the forum and I still don't know the answer.

gsxr · #5 02-05-2002, 02:34 PM

Yeah, I have the same problem with my '84, it gets 20mpg routinely. Then on one tank it got 24mpg! Then back to 20. (No, it wasn't bad math, that tank went over 400 miles where normally it gets to ~350.) Fuel quality can make a big difference, try a different diesel station. A workmate has an '85 300D and he gets 30-31 on the freeway (light foot).

There are mechanical things that can affect fuel conusmption but normally they also make the car run poorly. Try checking tire pressures, and make sure none of the brakes are dragging. Also check engine oil level, diff oil level, and trans fluid level. Make sure your air filter & fuel filters are clean too.

When was your last valve adjust? They're supposed to be every 15kmi, IIRC. Is your EGR valve functioning properly, or correctly disconnected? I've heard of people getting several more MPG by disabling the EGR.

If you figure it out, let us know. I'd like to hear what the cause is. Maybe start a new topic, with your specific year+model in the title, like "1984 300D - Runs Great, Crappy MPG - Why?"

:p

Good luck,

DIESELNATION · #6 02-05-2002, 03:44 PM

I also get the same fuel milage from my 84 300dt. I wonder if it is something specific to that year? Within the last 500 miles I have serviced the transmission, changed fuel filters, air filters, and cleaned the overboost protection valve. I am still getting 20-22 mpg.

the_good_fellow · #7 02-05-2002, 11:54 PM

I get 24+ ~ 25+ mpg pretty consistantly on 40/60 hwy/city daily driving. it has K&N air filter(+ 1.5 mpg). I used to get about 23-24mpg. Also I have 15" wheel and larger size tires. But I use the kick down switch quite a bit.

BWatson · #8 02-06-2002, 02:39 PM

On my last 2 tankfuls, I got 23 mpg with half a bottle of redline filled at a Chevron. Then I got 18 mpg with the other half bottle of redline filled at a Unocal 76 station. I just filled again at Chevron with 1/3 bottle so I'll see what happens. I have heard that better quality fuel leads to better mileage but I would have thought 76 would be high quality since the are at every truck stop I ever see. Also I see Diesel fuel ranging from $1.21 per gallon to as high as $2.00. I wonder why such variance? The Chevron station I go to is $1.21 right now on Vermont Av and the Hollywood fwy for all you Angelinos out there!!!

Larry Delor · #9 02-07-2002, 12:50 AM

When I drove it alot, I was getting anywhere between 23-27 mpg with my '83 300D. 95%highway..speed range between 70-80mph. Brand of fuel used most was Hess...occasionally Texaco ( with a "dose" of Diesel Fuel Catalyst).
Oil used was Castrol 20W50. A/C was on most of the time, Tire pressure checked regularly, and the tires where aligned. (the reason why I mention those things is because they can affect mpg in some fashion)
At this time it is getting a rebuilt engine installed. Once I get to drive it around a bit, I will check what this "new" engine will give me mileage wise.
-Larry

#10 02-07-2002, 11:14 AM

There was some discussion in a thread about timing chain life about how mileage tends to drop a few MPG when the timing chain gets stretched enough to retard the cam timing more than the factory recommended maximum (varies slightly per model). Have you had your cam timing checked lately, and do you have more than 200,000 miles on the motor?

BWatson · #11 02-07-2002, 11:49 AM

Well, for now, it seems to be running better from the Chevron gas I just put in and it seems like its getting better mpg so far. (only 25 miles into this tankfull but still registers above the full line on the guage). I have not checked the timing chain or valves since I bought the car in september but plan to to do so soon as it has close to 250,000 miles on it. I gotta find a new apartment first so maybe next month. I would probably not do it myself. I'm a pretty good mechanic but I would rather have it done. My mechanic is good and works on benzes all day every day. Also I know that the 85 models have a lower gear ratio in the final drive. I plan to change mine at some point because I understand you can get about 5 mph for the same rpm. So...at 3,000 rpm I go about 64mph. Add five and.....I still live for the day someone designs an overdrive add on for this car.

gsxr · #12 02-07-2002, 11:57 AM

Instead of swapping final drives, just upgrade to a 1987 300D!

Bunch more power, too (148 vs. ~125, I think.)

The 87's (W124) have something like a 2.27 rearend, which works out to 25mph per 1000rpm. Therefore:

1000rpm = 25mph
2000rpm = 50mph
3000rpm = 75mph
4000rpm = 100mph

It drives quite nicely at 100mph, and yes, the cruise control does work at that speed... (Montana, a few years ago, in case you were wondering.)

BWatson · #13 02-07-2002, 01:28 PM

I still like the look of my 82 better than the newer ones. It drives fine, maybe I'm just being fussy. I do like the more recent E class though. Retro styled and quite nice to drive.

TurboD · #14 02-09-2002, 12:59 AM

Actually it is a 2.65 rear end. It equates to about 85mph at around 32-3300 rpm's in 4th gear. I would know, thats what they clocked me at for my ticket when my speedo wasn't working

Palangi · #15 02-09-2002, 09:14 AM

After correcting for the odometer error, mine always gets about 22 to 23 mpg. Never varies much Doesn't matter if it is city or highway, fast or slow, uphill or downhill. I think most of them run in this range, although certainly some get mileage in the high twenties. I don't know why there is that much variation between cars.

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