Diesel blow by, high oil consumption, why?

I recently purchased some of your manuals and was checking out my newly purchased 82 300td and noticed it has excessive blow by and was 3 quarts low on oil after roughly 1000mi! I did your plug the breather trick and it goes for 3-4seconds before shutting down. This car starts great on frosty mornings and has lots of power, no smoke and no oil spots on the driveway. What do you think is the best method for freeing up sticky rings? (if that's my problem) I have a friend who fills his crankcase with biodiesel after draining the oil and idles for 10min or so. Do you think this is a bad idea? How can an engine run so well and use so much oil? I've had luck in the past using "Engine restorer" Any comment?

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Diesel Engine Specific Aid

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Chassis Model Number

W123

What to do?

Engine restorer, STP, motor honey, Instant Overhaul, etc. have been around for years and in some cases can help slow oil consumption and extend the life of a tired old gas engine. I can remember using them back in high school to keep my old stock 34 Ford going. Most if not all are oil viscosity enhancers to help seal rings, fill bearing gaps and increase oil pressure.

You can certainly try them and some could possibly help but don't be dismayed it you don't get much improvement. From all the engines I have worked on, I have found that they don't do much for a high mileage diesel engine with tons of blow by and high oil consumption. The reason - high internal engine pressure - 2 to 3 times what is produced in a gasoline engine. It all starts with a high cylinder compression ratio and transmits to more pressure on the piston, wrist pin, connecting rods and crankshaft. Case in point: If your run out of oil (lose oil pressure) in a diesel for just a few minutes the engine will be ruined. On the other hand, a gas engine might survive if shut down soon enough.

Excess crank case blow-by is caused by a poor seal between the piston rings and the cylinder walls. This can be caused by excess wear due to infrequent oil changes or poor air filter maintenance, foreign object damage, piston ring tension loss due to overheated engine, or just plain old age. Some engines will produce a good ring seal at low speed (ie startup) but lose the seal when the engine is running at high speed. Other engines will lose the seal at cranking speed and when that happens the engine will be very difficult to start. I have taken dozens of diesel engines apart and most of them have excessive cylinder wall wear. There is no quick fix for this condition and thickening the engine oil doesn't help much. The only time I have found seized rings was when the engine ran out of oil and got excessively hot. Most of the time I have found rings very sloppy in the piston ring grooves - once again due to high engine pressures.

EXCEPTION: If the engine is not worn out but has sat for a long time or has only been driven around town then a good high speed Italian tune up may help with the addition of a rich mix of our Stanadyne fuel additive in the fuel tank and fresh oil in the crankcase. Change the oil after 500 miles and repeat the process. When I say Italian Tune Up I mean at least two hours at 70 mph and above with the engine working hard! Pikes Peak climb would be ideal.....

I have seen diesels go for thousands of miles using a quart of oil every 300 to 500 miles. In some cases you just have to live with it unless you want to rebuild / replace the engine. There are two other things that could add to the high oil consumption - bad valve guide seals and / or a leaking turbo seal. In most cases those problems are associated with excess smoke at start up (valves) or excess smoke under acceleration (turbo seal). I offer a valve guide seal replacement kit with instructions on this website.

To find where your engine is eating oil, run the breather tube into a plastic bottle and monitor the amount of oil entering the bottle while you drive around town and when you drive a short distance on the freeway. If you are getting a lot of oil in the bottle then the oil consumption problem is caused by engine blow by. If not, then consider the possibility of failed seals mentioned above.

Please come back and post results after you have made some tests. Thanks, Kent