'98 E320 High Oil Consumption
 

My father has a relatively new to him '98 E320 w/ 60K on it.

It has burned a little more than a quart of (synthetic) oil in the last 800 mi.

There does not appear to be a leak - no puddles under the car. No blue smoke when driving.

He drives the car very little. He only uses it occasionally when he takes trips out of town - and probably only 1500 mi in the 8 mo he has had the car.

The first time we changed the oil and it was low we thought it had not been changed by the dealer - and had too many miles since the last oil change.

Any suggestions as to the cause? How to begin diagnosis?

Thanks,
Jeb

Hi JEB,

Which syn? If not Mobil 1 (or other higher end syns) I would change to M1 ... then, drive the living bejeezus out of it for a week ... extended ops at 80 MPH (or, leave in lower gear at lower speeds for same RPM) ... then, take a look and see what has happened.

With that mileage, can't imagine anything serious that would not be obvious in the operation.

**Bump**


Anybody have any other ideas?

Jeb

I have no idea what this engine has for a crankcase vent system. It probably has a PCV valve or some such.

Since the car is apparently driven only on very short trips I strongly suspect that there is some problem with the crankcase vent system. It may need a PCV valve and/or cleaning of the vent system.

When you are driving a car for short hops, say five or ten miles and never more, you really should be changing the oil and filter every 3 months rather than based on mileage intervals. The acids and moisture can build some really nasty sludge inside the engine.

Good luck,

Low Oil
 

When are you checking the oil level? This engine takes a long time for all of the oil to drain back to the oil pan and if you want to accurately measure the oil level you should wait at least 20 minutes after you stop the engine.

Used Mobile 1.

Probably should change the PCV if there is one - but would it cause that much oil loss - and where would it go?

The engine oil light came on while driving - so I think it was using oil - not just a symptom of how I checked the oil.

Should I try a leakdown test to see if it could be a valve etc?

Jeb

If you have made sure there are no leaks,do a compression and leakdown test it should tell you where the oil is going.

The first thing I would recommend is to place the car on a disciplined, rigorous oil consumption check. Check it frequently, consistently, and record the oil level and mileage everytime it's checked. The difference between the full and add mark will be explained in the owner's manual as will how to check the oil. Read it!

Most manufacturers recommend checking the oil with the engine fully warmed up a few minutes after shutdown, and the car MUST be on a level surface. A good way to follow this advice is to check the oil at fuel stops after you have completed fueling. Most pump island pads are level. Prior to fueling I remove the dipstick, wipe it down, and lay it on the cowl. This allows the oil to drain out of the dipstick tube, so when I insert the dipstick, I get a clear reading.

Once you are confident that you have an accurate data set that allows you to compute actual oil consumption, begin looking at causes if it is excessive. In my experience, most drivers have only a vague idea of their oil and fuel consumption because they don't keep accurate records, don't check the oil using a consistent process (or check it on unlevel surfaces) and end up with little more than a vague guess, which is often far off the actual mark.

Also, shortly following an oil change, oil level should be checked to be sure it was filled to overcapacity. Many "quicky" oil change joints don't use the proper oil quantity and some have reported that even MB dealers have under or overfilled their cars.

Although a quart every 800 miles seems high for the mileage, this rate of oil consumption will likely not cause any problems other than the inconvenience of checking and adding oil. Cars with functioning catalytic converters usually don't smoke because the oil that is not burned during combustion is oxidized in the converter, and as long as the car passes any required emission tests it's easier to add oil as required rather than tearing into the engine to find the cause, but a fuctional check of the PCV system is a good idea because it is mostly external and any problem should be relatively easy/inexpensive to correct.

Replacing valve seals, which is a common cause of oil consumption, is often a fix, but unless/until the oil consumption gets down to 300 miles per quart or about one every tank of fuel and you want to keep the car, it's a lot cheaper to add oil as required. There will probably be no other adverse affects if the oil consumption is at the rate you report.

Duke

Duke,

All records for the car are kept. It's company car and our mechanics keep very good records.

Oil level is checked after short use after oil change. It was filled to the proper level.

The Mobil 1 was 10-30. Would the lighter weight make a difference?

800 mi/qt seems too high and out of the "normal" range. My father is also worried about a catastrophic failure - as in a broken ring - stranding him.

60K seems pretty early to have to do valve guides. I have not been able to document such a problem - either here or on other boards.

Any other suggestions?

Jeb

Oil "disappearing"
 

What does the inside of the exhaust outlets at the rear of the car look like? If you wipe them out with a paper towel, do you get a black, heavy residue? If so, it's buring oil. (I don't know what the residue looks like for synthetic oils - I'm just guessing.)

Looking for a big problem is always an honorable thing to do ... however, this sounds increasingly like something simple ... i.e. one valve stem seal, etc ... not likely there is a major ring issue ... as one of the other posters noted, 800 miles per quart is considered within "normal" range for some manufactuers ... people don't like to hear it, but it has held up in court.

My wife's suburban uses about a quart every 1200 miles ... has from day one to now with about 60K on it ... runs extraordinarily well ... just uses a bit of oil.

Drive it hard for a 1000 miles, then start religiously tracking oil usage.

Oil Weight
 

Check your owners manual for the proper oil viscosity for the outside temperature you are operating in. Mercedes does not recommend 10W30 weight oil for anything.

As suggested, check your owners' manual and use a SAE weight oil that is recommended for the ambient temperature range the car will see over the interval that the oil will be in the car. High oil consumption does not lead to catastrophic failures and a broken ring will cause lots of blue smoke (despite the converter) and poor performance, but the engine won't quit. There's essentially no risk of a catastrophic failure due to the relatively high oil consumption.

If he's really concerned have a compression or leakdown test performed. If the numbers are good there is nothing to be concerned about. An engine can have excellent compression/leakdown numbers, but still have high oil consumption due to valve guide wear and/or deteriorated vavle seals. Bad guides or seals just cause high oil consumption, but don't necessarily cause any operational problems or reduce engine performance.

I replaced the valve guides on my Cosworth Vega two years ago when oil consumption degraded to a quart every 100-200 miles. The engine ran fine and had good compression and leakdown numbers. The OEM valve seals were never very good to begin with and the guides were severly worn. New guides and a new seal design that I found reduced oil consumption to a quart every 5000 miles. Despite the severe valve guide wear, there was no measureable wear on the aluminum/silicon cylinder bores.

In 1979 a friend of mine bought a new Porsche 911 SC, and it used a quart every 600 miles from the get-go. Porsche said it was within the normal and acceptable range!

Duke

A 1998 E320 should be an FSS type car, and there are a number of FSS equipped vehicles that were not maintained using Mobil 1, 15W-50 or 0W-40, that can suffer from oil related damage. The damage is a result of owners delaying oil changes until the FSS system told them it was time, when they did not use synthetic motor oils of the approved variety. The FSS system bases its intervals on using those Mobil products. Non-synthetic oils cannot support such extended change intervals.

Since the requirement to use Mobil 1 of the varieties noted was not clear in the manual, or apparently to the dealer service guys, Mercedes-Benz settled a class action court case by offering every FSS car an extended warranty against oil related failures for up to 150,000 miles. So, if you have an oil related failure and you have been using Mobil 1 since you got the car, you may be elligible for a free fix on MB, if there is a significant problem.

Good luck, Jim

It is my understanding that the extended 150K mile warranty only applies to the original owner. If you are the second, third, ... owner then there is no extended warranty.

The only thing Mercedes sent me was a letter recommending the use of synthetic motor oil.