123 300D-T poor mpg! What do you get? HELP!!
 

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?

Odometer innaccurate, Dragging calipers?

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.

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.

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.

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.

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!

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.

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?

swap in a stick and you will get close to 30MPG, and you wont have to deal with the 240 sluggishness

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

:DX2 on the ebay cars and they will last 1,000,000 miles :D

I have been through this with my 240d (4-sp). By doing everything suggested above and also going easier on the throttle I have moved from about 18mpg to 20-21 in the city. Still pretty underwhelming for a 240D with std. transmission.

The last thing I plan to do (suggested above) is get my injectors rebuilt and also replace the timing chain.

I think this is the underlying problem for my car.

82 300CD turbo with 4spd and 2.47 rear. I consistently get 31MPG highway/surface mixed. I hardly ever run slower than 70MPH on the highway.