Using a 5w 40 synthetic oil, is the oil thinner when hot or cold and easier to suck up through the dip stick tube. I worry about the hot oil melting the plastic parts and tube on my suction system.
EDIT: There seams to be some sort of obstruction in the dip stick tube that wont let me get a 1/4" copper tube to the bottom of the pan. I am unable to get as far down as the dip stick goes. Has any one changed oil this way?

__________________
1984 300SD turbo 126
"My true love"

God made me an atheist and who am I to question His wisdom

It is best to change the oil when hot.

I understand the appeal of suction oil changes, but I don't trust that they are as effective as draining from the bottom of the sump. No, I have not changed oil that way. I pull the plug and let it drain for 15 minutes after removing the oil filter first. Not saying it is the right way, or the only way... but it works.

That is the way I have always done it as well but of late I do not enjoy crawling around under a car. It's an age thing.

__________________
1984 300SD turbo 126
"My true love"

God made me an atheist and who am I to question His wisdom

Oil should be changed hot, the nylon lines and the tank should be designed to withstand it. I've used an Oilboy for fifteen years or so, on three different Benz's. I use it on all my cars except the Subaru, which isn't set up for an extractor. It may be that your '84 has a similar problem.

As for draining all the oil, get over it. When I changed the pan gasket in my 190DT, I drained the oil by suction and found only an ounce or so remaining in the pan. It's as effective as draining by the plug.

One tip. The tubes are a mess to store. I took a couple of lengths of 3/4 copper pipe, and soldered caps over one end. The suction tubes go into the pipes for storage. Anything that drips down stays in the pipe.

I have just done an oil change using a vacuum system, get the engine up to temperature after a drive around and then go and make a coffee, come back and the engine oil was warm but not hot.

Ideally pulling the sump plug is best and I will be doing a 'proper' oil change every other oil change. I have however found that using a vacuum oil change system is so much easier (as long as the dipstick tube is a good enough bore to get a decent tube down there!).

__________________
UK spec Mercedes W210 E300 Turbodiesel wagon - OM606.962 with 722.6 transmission - rust free!

The dipstick tube extends to the lowest point in the sump. It is designed to have the plastic extraction tube attached at the top and does not require a plastic tube to be inserted through it. This is the way the dealer service department would do it. The MityVac includes such a seal for the tubing. A drilled rubber cork would accomplish the same. By doing so, the extraction will be much faster and more thorough.

Try this experiment. Next change, suction your oil using that method. After the suction is complete, crawl under the car and remove the drain plug. See what comes out. You will find a few drips or nothing at all.

Hmm not thought of it like that, have only ever seen vacuum systems putting a tube down the dipstick hole, usually the top of the dipstick is flared slightly so might not give the best fit - will try that next time!

__________________
UK spec Mercedes W210 E300 Turbodiesel wagon - OM606.962 with 722.6 transmission - rust free!

I do it the way RockyRacoon described. Also have the larger Mityvac. Just remove the smaller tube and plug the rubber stopper reducer into the dipstick tube.

Works great on my 85 300D and 98 E320. Never have to go under car

But not on V-8 350SL. There I use the smaller tube down dipstick tube to get most of oil out before going under car to remove filter. And before that take out drain plug to get any remaining oil out.

The plastic does get soft if the oil is really hot. I just go for a 2 or 3 mile run to warm up oil before changing.

__________________
Graham
85 300D,72 350SL, 98 E320, Outback 2.5

If you want to avoid under car drain but want to drain from the pan, add a hose to the drain plug and bring it out to the front of car / stow under hood. This is commonly done on industrial / construction equipment where direct pan access is difficult.

Use 300 PSI fabric air / oil hose and pushlock fittings if you can protect the hose, single / double wire hydraulic hose of abrasion is a concern. There are metric straight thread to JIC fittings out there but you must search through catalogs to find a matching thread. If you can't find the proper thread something will need to be made.

Cap the end of the hose with a JIC fitting ( 37* flare ) or a SAE ( 45* flare ) . If you are concerned about a leak stow the hose above the oil level, though this setup is no worse than a regular drain plug.

Thanks you all for the discussion and good information. Rocky Racoon you make it sound so simple. I will try your method.
Thanks.

__________________
1984 300SD turbo 126
"My true love"

God made me an atheist and who am I to question His wisdom

I don't claim to be an expert on all Benzes, but my dipstick tube does not go to the pan on my 300D. I have to be careful to feel the suction tube hit the pan because if I keep pushing I can feed the entire tube into the crankcase and the end often goes above the oil level and sucks air. So I subscribe to the suggestion that if you suck from the top of the dipstick tube, also pull the drain plug to be sure you are getting all the oil out. My drain plug is no longer removable but the plastic suction tube down the dipstick tube works well. It takes maybe 15 minutes. Time enough to loosen the filter and let the filter drain into the pan.

On my engine the dipstick tube and the drain plug are both on the front of the long straight 6. If I were to drive on ramps so I could use the drain, if it were working, large amounts of oil would be left in the back of the pan. I park with the front slightly down hill and believe I am sucking as much out as practical, although some is likely still in the oil cooler.

Oh, and the oil is much thinner when hot. It will take a long time to suck out cold oil, but it will work if you are patient.

__________________
'97 E 300 D

Well, that didn't work and what a mess. Filthy tubes and vacuum fittings to clean up. The dipstick tube on a 84 126 just goes into the oil. Not all the way to the bottom. When vacuum is applied the oil just gurgles in the pipe as air is sucked in.

Plan B: I inserted a 3/16" hard plastic tube (vacuum tube) down the pipe till it hit bottom, switched on the vacuum pump and oil appeared in a few seconds and the oil s l o w l y rose in the tank at a rate that said I would be doing this all day. Another cleanup job after this failed Plan B.

Then I discovered a little screw plug in the bottom rear of the oil pan.
Dropped the oil into a tray and in a few minutes I was finished with only a tray to clean up. Gee, what a great way to do an oil change.

Signed: Disgusted.

__________________
1984 300SD turbo 126
"My true love"

God made me an atheist and who am I to question His wisdom

Dear Disgusted,

A solution to your problem was the subject of yesterdays column ( # 9 ) Yes, it takes a bit of work up front but the results are worth it. Perhaps someone will post the thread size so we can locate a suitable adapter.

However, be aware that looking under the car during an oil change is always a good idea even when draining top side.

Not sure how many people know about these.

Search results :: Qwik Valve

They're pretty sweet.

__________________
Current fleet
2006 E320 CDI
1992 300D - 5speed manual swapped

former members
1984 300D "Blues Mobile"

1978 300CD "El Toro"

I looked at those in past. With adapter plus valve, are they not a bit vulnerable? Maybe not on W123, but I think it was for my R107 that I considered them.

On my 85 W123 and 98 W210 gasser, the Mightyvac sucking through the dip tube works just great.

__________________
Graham
85 300D,72 350SL, 98 E320, Outback 2.5