First long trip in $800 300 D 23 MPG is that good? - PeachParts Mercedes-Benz Forum

RichC · #1 12-22-2005, 10:30 AM

We just made it from Norman Oklahoma to Lincoln Nebraska on one tank of Diesel ( 20 gal ).

The distance was 453 miles so thats around 23 MPG.

Is this average for an 1981 300 D ?

What is average for this car?
It is a 5 cyl, 3.0 liter automatic.

Just bought this car off ebay not long ago for $800. And I'm loving it.

Looking forward to burning veggie oil and biodiesel.

Thank You this is a great group.

R Leo · #2 12-22-2005, 10:51 AM

Seems low...Any fuel leaks? Does it roll easily on level ground? Is that the elapsed miles reading from your odometer? It is possible that your odometer isn't registering all the miles you've driven (sometimes they slip and under count the miles).

dannym · #3 12-22-2005, 11:42 AM

Hey,
That does seem low but not as bad as my mileage was at first. I was only getting 18mpg when I first got it. Now I get around 25-26mpg. I believe the 300D should do better being a lot lighter.

The manual says for performance issues to check timing.
I would check the timing and correct with a woodruff key, which is what I did or some people will recommend to replace the chain if it's stretched.
Click this link for cam timing instructions, choose section 05-215
While you have the valve cover off adjust the valves. Section 05-210

As Leo said check for fuel leaks and replace fuel filters. Pay attention to the rubber fuel return lines on the injectors. He mentioned if it rolls freely. If not you can have dragging brakes or you may need to repack the front wheel bearings. The wheel bearings are a maintenence item you should probably do this anyway.

If you continue to have performance issues you can clean the injectors.

Welcome to the wonderful world of DIY!!

Danny

Matt SD300 · #4 12-22-2005, 11:50 AM

Quote:

Originally Posted by RichC

We just made it from Norman Oklahoma to Lincoln Nebraska on one tank of Diesel ( 20 gal ).

The distance was 453 miles so thats around 23 MPG.

Is this average for an 1981 300 D ?

What is average for this car?
It is a 5 cyl, 3.0 liter automatic.

Just bought this car off ebay not long ago for $800. And I'm loving it.

Looking forward to burning veggie oil and biodiesel.

Thank You this is a great group.

I have had a couple of these cars and your mpg seems just fine (normal)

If you need any help with running veggie oil E:MAIL me. Enjoy the car!!

boneheaddoctor · #5 12-22-2005, 11:55 AM

I get 25 in a 50/50 mix of highway and stop and go driving or mountain highway driving....but get 29 on flat highway driving...but then I have 150K miles and thats low compaired to many here (as far as toal miles), I don't think a car wth 300K or more miles would do that well.

Palangi · #6 12-22-2005, 04:39 PM

My 300D gradually worked its way up from 22~23 mpg tp 26~27 mpg. I can't explain it, but I am enjoying it.

tjohn · #7 12-22-2005, 05:19 PM

Orginal EPA estimates for this car was 22 MPG, so 23 is not necessarily a problem. That said, many many people here do better. Proper valve adjustment is essential, and proper timing. One thing you want to be absolutely certain of is that you are measauring your mileage correctly. I was troubled by a mysterious decline in my mileage from 25 mpg average down to 18-19. I did valves, IP timing, swapped out calipers, replaced fuel return lines, everything I could think of. It turned out my odometer didn't accurately track my mileage. It would be fine for a long time, and in fact I checked it for 2 or 3 miles against highway mile marker signs, and it was OK. Finally, though, I took a couple long (400+ mile) trips that I did portal to portal using MapQuest. MPG calculated that way was 25-27, just like always. A bit later the odometer failed completely, so I think the gears were just beginning to slip.

RichC · #8 12-22-2005, 06:30 PM

I think there may be small fuel leaks at the injector. I have already replaced the fuel return lines, they looked scary

That or oil from the valve cover gasket.

It does roll easily, and I have repacked the front wheel bearings. Nothing else is dragging, like the brakes or the inner parking break that I can tell.

I have adjusted the valves.

The mileage quote came from mapquest and was verified by other vehicles. But I do have smaller diameter tires on the car and I know this would account for some of the fuel consumption.

I have not looked at the timing, or timing chain. The car has 125,000 miles on it, I hope the chain is ok. Thank you for the timing chain link dannym.

I hope to be getting a can or two of the lubra/liqua molly soon to run through the injectors.

Matt SD300 I will probably take you up on the offer for help in running veggie oil.

Almost all of the miles were highway miles at an average speed of 75 mph. ( that is adjusted for the smaller tires ) speedometer reading 75, car actually traveling 70 or so.

I'm hoping for an increase in mileage as the engine wears in again. The car had been sitting for about two years.

I really like this car, and enjoy this board. It is good to have people like you guys to help. I hope I am able to return the favor.

How hard is it to change the timing chain on this car ?
Could the IP timing be affecting the MPG ?
Could the ALDA setting affect the MPG ?
Anyone want to sell a can of lubra molly cheep ?

Thank you for the help and the input.
It is much appreciated.
RichC

dkveuro · #9 12-22-2005, 06:55 PM

What do you expect ? Your trip, according to my globe of the world, is all up hill......you can expect better mpg coming back down !

Most run 23 to 30 mpg.........your driving style/terrain/distance/windspeed/tyre pressures/tread type/brake drag/load/ambient temperature, etc...all have an impact.

.

tjohn · #10 12-22-2005, 07:19 PM

Quote:

Originally Posted by RichC

I'm hoping for an increase in mileage as the engine wears in again. The car had been sitting for about two years.

Oh yeah, that definitely can bring down the mileage. You need to blow the carbon out real well. Find a highway with some nice steep hills - the kind that the big rigs have to move into the right lane because they slow down so much - then floor it until no more black smoke comes out.

PagodaLover · #11 12-22-2005, 08:01 PM

I bet your mileage gets better as you drive it. It's not that bad at all for a w123, really. Plus it's $800 and getting 23 mpg and drove you 400+ miles no problem. Very nice, indeed. I would think all that was great.

JimmyL · #12 12-22-2005, 08:40 PM

Something else to remember. Being an '81 300D makes that a non-turbo, so you actually lose some effeciency on the highway. Also, I imagine the gearing is lower also.
Nice job on finding an inexpensive (up front

) MB! How small of a diamter are you referring to on your tires?

boneheaddoctor · #13 12-22-2005, 08:49 PM

run a few tanks of B20 it its availible to you or B100........tht will clean things out pretty well, so can an Italian tuneup.....

#14 12-22-2005, 09:09 PM

For $800 BUCKS it would have been excellent even if it did only 20MPG!

RichC · #15 12-24-2005, 12:27 AM

I have done the Italian tune up suggested. That is one of the first things I do to an old car that I buy. It cleans things out and if anything is about to break you can find out then and not in the middle of a long trip. I like the Idea of doing it uphill for more effect, thanks.

I have not heard of the B 20 or B 100 what is it ?

The tire size is 195/60/14 Bridgestone Potenza G009.

The car will receive more city driving than long distance, I thought the smaller tires would give me a little more power at take off. Plus I like the lowering effect and the better handling.

I think I will get a second set of tires and rims that are taller for long distance trips. They will probably pay for themselves in mileage savings.

I may have a chance to purchase an 82 300 TD cheap soon.
The engine was ran without oil, and is dead.

Do you think the turbo was fried along with the engine ?
Is there a way to tell if the turbo is ok ?
Is it hard to transplant the turbo from an 82 into an 81 300 D ?
If I get this car I will part out the things I don't need to you guys cheap!

Thank You all.
I love this board.
Makes owning an old Mercedes that much more fun.