My '79 240D is burning a quart of oil every 300 miles. The car does'nt drip too badly on the driveway, so I don't think I'm losing a lot of oil on the road. The question is: If I switch to synthetic how much will my oil consumption go down, and are the emissions from the synthetic any worse than dino ? The car runs very well, and I've been running biodiesel in it for almost 5 years now. If all of this burned motor oil is canceling out the improved emissions from biodiesel, I might be looking at a rebuild, or another car.

Check your vacuum pump diaphragm. If it has a tear, it will feed oil directly into the intake. Look at the line that goes from the vacuum pump to the air cleaner and see if there is oil inside it. Or take it off while the car is running and see if oil is coming out of it.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

I don't think using synthetic will reduce oil consumption if it is caused by worn rings and bores.

Since synthetic is a lot thinner than dino, using it will reduce your supply of money dramaticly though!

Tom W

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I have noted that using Mobil Delvac 1 in an old, oil burning 240D with over 250,000 miles changed the machine's performance significantly. The compression improved and oil consumption going through the engine decreased as was evident at the tailpipe - objectionable smoking just went away and the car started much easier and reliably even in near zero degree Fahrenheit temperatures. The engine had a relatively serious rear crankshaft seal leak that ultimately led to the end of the engine's life, but only after about a 120,000 mile workhorse role as the car used by 2 of my kids in Troy, NY while at college which included towing jet skis between Lake Champlain and the Connecticut shoreline all summer.

The point of this is a few oil changes with a good, Diesel rated synthetic like Delvac 1 can clean out the ring grooves, and return the engine to a condition where it can operate to the best of its potential, given its actual condition. If it is actually cylinder bore/piston ring wear, no oil will fix that. If it is a buildup of combustion products that are preventing the rings from doing their job, or adversely affecting oil flow through the engine, that can be "cured" with a couple of oil changes. I would give Delvac 1 a chance before tossing the car to the junk pile. May cost you a couple hundred dollars total over the next 10-15,000 miles and add another "lifetime" to the car's useful life to you.

Good luck, Jim

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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

Thats interesting, as I would have tended to agree with Tom, but it stands to reason that if your burning oil because of stuck rings, synthetic oil might help, as in your case. I had a leaking rear main seal on an engine I rebuilt for my 240D and Amsoil slowed the leak to almost zero after 15-20K.

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

I don't disagree with jim.

Tom W

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Wish I had known about curing that leak with Amsoil. We took to parking with the nose downhill, and never filling it past the middle between the high and low marks on the dipstick. Otherwise, it leaked to that level in no time. And, my son was less inclined to follow the rules than my daughter and it was ultimately his negligence that led to the engine being run too long under too much load with too little oil. Never siezed but the machine just begged to be put to rest at about 321,000 miles.

One other thing, my kids drove the car up and down some pretty steep hills in Troy, never getting out of second gear, and always with the pedal to the metal. This also helped keep the inside of the engine free of soot and crap - kind of a daily or at least bi-weekly Italian tune up. And we instituted a minimum 20 minute run in the winter to ensure the oil got warm and the charging system kept the battery in good shape.

Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

You might also try replacing the valve stem seals next time you need to adjust the valves.

I dont think Amsoil did a better job than Mobil would have, they are both made from the same base stock. I still only fill the oil to half way between the marks and make sure it stays there.

__________________


1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

I forgot to mention that there's enough blow-by coming out of this engine to send the oil filler cap on to the driveway. If anyone thinks that replacing the valve stem seals would make a difference, then I'll go ahead and do that, but I'm guessing that the rings are the real issue. Thanks
BTW, I checked the vacuum pump hose, and it's clean.

Might be worth the effort of soaking the rings with marvel mystery oil for a few days with the block heater on. It cleans the gunk out of the ring lands as well. A lot cheaper than synthetic with your present base oil consumption rate.
We have had biodiesel do some funny things as well up here so the soak might be important. You quoted burning it for the last five years.
Another approach is to use straight 40 weight oil. That should cut your consumption in half. Probably better for worn engines anyways. You do live in a moderate climate compared to me.
The forty weight should not hinder starting too much on cooler mornings. Forty weight has a lot more viscosity than 15-40 to seal rings you will find. It always reduces consumption. Your valve rubbers are probably not a real issue unless they have rotted away in your climate.