123 300D-T poor mpg! What do you get? HELP!! - PeachParts Mercedes-Benz Forum

Hip001 · #1 06-17-2009, 07:42 AM

I just picked up a SWEET 1985 300D Turbo. 206k miles, Beautiful car inside and out. I checked the mpg after filling up the 2nd time. 18.5mpg

????

I was told be the previous owner that 30mpg was the norm and told by Pierre that 28ish mpg could be expected. What the heck is knocking it down 10mpg?? Pierre said he thought my valves need adjusting(they are tight he said). Is this alone the problem or are there other factors?

What car do you have and what MPG do you get?

fruitcakesa · #2 06-17-2009, 07:53 AM

Odometer innaccurate, Dragging calipers?

Hip001 · #3 06-17-2009, 07:59 AM

I checked the odo with my GPS and when running 70 it is actually running 67. So I understand I may be getting slightly better than 18.5 Maybe 18.8mpg. Would I not smell the brakes if they were dragging? I'll drive it home today(25 miles) and touch the wheels to see if they are hot.

I wanted the 240 for the better mpg but was told the 300 can actually get close.

#4 06-17-2009, 08:09 AM

I would second valve adjusment and diesel purge and might want to look into injectors. I would also ask have you changed all fluids? I would also recommend to check to see if your turbo is working properly and to clean your banjo bolt on the back of the intake manifold. I am sure others will have better ideas hope this helps.

toomany MBZ · #5 06-17-2009, 08:16 AM

You may have weeping jumper fuel lines. Check around for any leaks throughout the fuel system.
Adjust the valves, but that shouldn't dramatically lower mpg.
Anytime you purchase a 24 year old car you may want to do a fluid and filter change, oil and transmission. I'll agree with a purge too, but that's more of a performance issue.

kerry · #6 06-17-2009, 08:27 AM

30mpg figure is not true. Search on here and you will find 24-25mpg is the norm for a 617.

Hip001 · #7 06-17-2009, 08:49 AM

Quote:

Originally Posted by kerry

30mpg figure is not true. Search on here and you will find 24-25mpg is the norm for a 617.

Ouch! Well then I'll prob sell the 300D-T and keep my search going for a 240D 4spd. I just bought it because it is in awesome shape and rust free!

snookwhaler · #8 06-17-2009, 09:35 AM

Check your odometer against a GPS or measured mile. Not the "Speedo" as you listed above. Use a GPS that shows the distance you have traveled in 10ths of a mile. Your speedometer error is one thing the odometer is another. Mine is actually about the same as yours with the Speedo. But the odo is 20% off!

I have found that if I follow my odometer and use that figure against what I put in at the pump. My mileage is only 21.3.

After using a GPS and having the odometer apart now I know that my odometer is exactly 20% off. This puts my mileage right at 26 to 27 MPG. I have been checking it ever since I bought the car and it always the same. Usually 26.3 sometimes a little more.

I don't believe 30 MPG with an automatic. Unless you are up in the mountains. Even then I have a hard time believing that. Maybe with a car modified with a stick.

Hip001 · #9 06-17-2009, 09:44 AM

Gonna drive it to Orlando on Saturday. I'll GPS the miles then and recheck my figures to that. for some reason the cig-lighter will not securely stay plugged in?

t walgamuth · #10 06-19-2009, 05:50 AM

Quote:

Originally Posted by kerry

30mpg figure is not true. Search on here and you will find 24-25mpg is the norm for a 617.

x2 seventeen to eighteen around town and low to mid twenties highway is what I got. To get better you have to swap in a taller rear end. The wagon is at least two hundred pounds heavier than a sedan.

thirty highway in a two forty d is about the max under ideal conditions, mid to high twenties is more normal for one with a stick. with an auto it will be four to five less.

its really pretty good mileage for its day.

charmalu · #11 06-19-2009, 12:19 PM

These are my milage totals since 4-10-09 since the 4-spd swap in the 85300D
27.86, 31.94, 26.98, 27.89, 29.68, 27.09, 28.40, 30.79, 26.87, 30.05, 32.21,

24.47, 28.18, 26.87, 29.01

this is an increase over the automatic 2 - 3 mpg.

the 31.94 is a trip back from carson City, NV back to Calif. over HWY 50. more down hill on the Calif side.
The 32.21 also a trip back from Carson but over HWY 88, highest elevation is over 9000ft.

there is also two trip to Portland, OR. and back to Calif.
the 26.87 is when I had my foot into it doing 70 on this last trip to Portland, so it droped some. most of my driving is doing 60 or so with the tach around 3000RPM.

the rest is freeway and in town driving. It really amazes me when I get 27 or more from my in town driving. I do have the 2:88 Differential.

we will be leaving portland on Monday for home, so we`ll see what we get on that leg. It is a 700 mile trip.

Charlie

lutzTD · #12 06-19-2009, 12:36 PM

Quote:

Originally Posted by charmalu

These are my milage totals since 4-10-09 since the 4-spd swap in the 85300D
27.86, 31.94, 26.98, 27.89, 29.68, 27.09, 28.40, 30.79, 26.87, 30.05, 32.21,

24.47, 28.18, 26.87, 29.01

this is an increase over the automatic 2 - 3 mpg.

the 31.94 is a trip back from carson City, NV back to Calif. over HWY 50. more down hill on the Calif side.
The 32.21 also a trip back from Carson but over HWY 88, highest elevation is over 9000ft.

there is also two trip to Portland, OR. and back to Calif.
the 26.87 is when I had my foot into it doing 70 on this last trip to Portland, so it droped some. most of my driving is doing 60 or so with the tach around 3000RPM.

the rest is freeway and in town driving. It really amazes me when I get 27 or more from my in town driving. I do have the 2:88 Differential.

we will be leaving portland on Monday for home, so we`ll see what we get on that leg. It is a 700 mile trip.

Charlie

If you do a lot of long trip driving you might want to look at putting in a 2.47. 60MPH turns around 1900 and 70 is around 2300. very quiet and confortable ride and should get you another couple MPG

Hip001 · #13 06-26-2009, 08:50 AM

Quote:

Originally Posted by charmalu

These are my milage totals since 4-10-09 since the 4-spd swap in the 85300D
27.86, 31.94, 26.98, 27.89, 29.68, 27.09, 28.40, 30.79, 26.87, 30.05, 32.21,

24.47, 28.18, 26.87, 29.01

this is an increase over the automatic 2 - 3 mpg.

the 31.94 is a trip back from carson City, NV back to Calif. over HWY 50. more down hill on the Calif side.
The 32.21 also a trip back from Carson but over HWY 88, highest elevation is over 9000ft.

there is also two trip to Portland, OR. and back to Calif.
the 26.87 is when I had my foot into it doing 70 on this last trip to Portland, so it droped some. most of my driving is doing 60 or so with the tach around 3000RPM.

the rest is freeway and in town driving. It really amazes me when I get 27 or more from my in town driving. I do have the 2:88 Differential.

we will be leaving portland on Monday for home, so we`ll see what we get on that leg. It is a 700 mile trip.

Charlie

My 1st two tanks were 18.5, 23.9 mpg. The current tank is since the service(Valves, fluids, intake de-gunking) hopefully the mileage is up! I'll know this weekend sometime!

Hip001 · #14 06-17-2009, 08:26 AM

Thanks guys!
I'll do the valves soon. Not noticed and weeping lines. Motor looks dry. My mercedes mechanic (Pierre) looked it over yesterday and said it is a sweet car! He mentioned the valves but when I was there it was before I knew about the poor mpg.

::matthew · #15 06-17-2009, 10:22 AM

buy one on ebay...they get 40-50mpg