RESULTS: OK to OH trip (Oil Consumption??) - PeachParts Mercedes-Benz Forum

rgnprof · #1 05-31-2006, 02:06 PM

I took my '78 300D home to Ohio this week (had to attend my nephew's graduation). Car ran great, A/C and cruise worked well so I was basically happy.

I drove it 2250 miles (almost all 65-75 mph), used 100 gallons of diesel for a mileage of 22.5 mpg. That is with the A/C running most of the way (I have discovered that the only way to stay comfortable is to always run the ACC - otherwise I get pretty warm air lightly blowing out the vents and the cabin heats up pretty quickly).

Does that sound about right - 22.5 mpg? This is a non-turbo 617.

My only concern is about oil usage - I bet I used about 4 quarts making the trip and that seems high to me. I changed the oil before I left, Chevron 15-40. I have no external oil leaks anywhere, air filter is clean and the only time I notice smoke is when I start the car and first drive it. After it is just a little warm, no smoke is noticeable.

Any ideas? Should I just be happy since the car ran very well - and keep a steady supply of oil on hand?? Or am I looking at trouble down the road...?

Ryan

1978 300D

BobK · #2 05-31-2006, 02:54 PM

Speed didn't sound too high, so I don't think that was the cause. How high up on hte dipstick do you fill the oil? Current thinking is to fill to half way between the red marks. If you fill all the way to top mark, there have been reports of high consumption.

Brian Carlton · #3 05-31-2006, 03:02 PM

Without a turbo, you either leak it or you burn it.

In your case, you have no external leaks.

Not much you can do about burning of oil........just manage it.

As mentioned, keeping the level near the low mark sometimes helps.

Even after a complete overhaul on the head, the SD drinks close to one quart every 1250 miles. I've got a suspicion that the turbo is the culprit.......but.......you never know.

barry123400 · #4 05-31-2006, 03:51 PM

You might just want to make sure the vent line from the vaccum pump to the intake area has no oil in it. These older models are a little different. Not likely but should be examined. Air filter have a lot of oil residue? Much blowby out the oil cap hole? As mentioned if you fill oil to the top mark a lot of people report rapid initial oil consumption until the mid point has been reached.

#5 05-31-2006, 04:04 PM

The oil consumption sounds a little high (my 617 uses almost a quart in 2000 miles), but your probably not going to hurt anything unless you let the level get too low.

Your fuel mileage seems a little on the low side for highway driving. You may want to check valve adjustment and IP timing. I don't know how many miles you have on the car, but timing chain stretch can through off the timing.

t walgamuth · #6 05-31-2006, 07:17 PM

although i once overfilled my 603 (by accident) and noted a problem, i have often driven my 616s and 617s a little over the top mark (not intentionally) and not suffered any ill effects. if i had a car that was using a lot i would for sure fill it to the top each time, especially a 616 617.

tom w

rgnprof · #7 05-31-2006, 10:44 PM

Thanks for the replies!

I need to check the timing chain stretch - I think I read an earlier post on how to do that. I did adjust the valves after I got the car, but I am real confused about how to check the IP timing on this car?? And I have been pretty careful about filling with oil - try to keep level between the 2 marks on the dipstick.

I think I will check the compression and maybe replace the valve stem seals - doesn't sound too difficult on this car.

I do have blow-by, but I'm no expert - it is hard to tell how much? From what I have read about blow-by on this forum, mine seems normal.

Ryan

sailor15015 · #8 05-31-2006, 11:34 PM

So oil consumption increases at constant highway speeds. Hmm. My commute to college and back is along a highway with a speed limit of 65mph. I'm going to California next week and will be doing a lot of 70+mph driving so I wonder if I'll see an increase. If I don't do anything to the oil system(i.e. remove the cooler lines or introduce some other leak) it needs a half quart if any between fillups.

Teemeister · #9 06-03-2006, 02:44 AM

my 300 D also used about a quart on a 500-mile highway trip at 70 mph avg., yet it does not smoke. I remember getting quite good mpg on that particular trip, close to 30, with all the special features turned off

. The oil was exactly the same: a Chevron 15W-40. I'll try a higher viscosity oil next time because I assume that the Chevron could be a reason for the high consumption. Anyone else has had a similar experience?

t walgamuth · #10 06-03-2006, 04:26 AM

i wouldnt go any higher on the weight of oil.

in fact i dont know if you can.

tom w