I realize that this has been covered in the past, but it's been covered so many times that I just can't sort through it all. Basically I am wondering if I should switch to synthetic oil. My car is a 1987 560SEL (168k), and I have heard (here and elsewhere) that switching to synthetic on an engine that has seen too many miles with dino is not a good idea. However, synthetic seems to have so many advantages to dino oil, perhaps it would be a good idea. The car was maintained perfectly until December 1999. At that time it was sold to someone who, aside from oil changes did nothing to it. I bought it in August 2000 and replaced all fluids and filters (just to be on the safe side) as well as taking care of a few other neglected items. I would like to try to make up for the 10 months that the car didn't get TLC it needs and deserves. Any opinions would be appreciated!
Justin

Searching through this data bank you will surely find that this is a much debated topic. People can get rather passionate about it too! Personally, I don't think it much matters which oil you use, synthetic or conventional. Simply use the oil of your choice and an OEM filter. Follow the advice of "Oil Guru" Larry Bible-"Change it hot and change it often"-and your car will be getting the TLC it needs and deserves.

Primo

My car has 90k miles on it and I recently changed to synthetic. Actually at my last oil change, I put in 3 quarts of Mobil 1 synthetic 10w-30 (that's all they had), and then 5 quarts (a big jug) of Mobil 1 10w-40. I have yet to have any leaks, and car runs as good as ever. My next oil change is going to have 5 or 6 quarts of synthetic, and 2 or 3 quarts of dino, respectively.
I'm doing a transition just to make sure it goes ok. I am going to push oil changes to 4k or 5k with the partly (and then fully) synthetic oil.
But everything's fine so far!

__________________
2006 E350 w/ 155k miles (Daily Driver)

Previous:
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)

Way easy.

Clean oil is way better than dirty oil.

Synthetic is way better than conventional oil.

This issue, technically, should no longer be devisive. Those that disagree now with the use of synthetic oil are likely to have disagreed when it was first available, and are likely to disagree until they die.

But remember, that does not mean there is a logical, technically accurate debate. It simply means that there are some (smaller number each year as the knowledge sinks in) who disagree.

George

Hey Dave C Klasse, Isn't mixing oil viscosity a bad thing (10w-30 and 10w-40) I thought manufacturers said never to mix viscosities?

I bought '79 300SD for a parts car and it ran so good I've been driving it for 3 years now and 33,0000 miles. It had 160,000 miles on it when purchased. Since I wanted to preserve the engine in case I needed it for my '80 300SD, I put in Castrol Syntec 5W50 because I use it all year round.
Originally it used 3 quarts in 10,000 miles (change interval), then 2 quarts and now at 93,000 miles (3,000 miles after last change)it is barely off the full mark. So the synthetic seems to be improving the engine. NOTE: I also add about 4 ounces of PTFE at each change whch may also be partly responsible for the improvement. Here's my motto: "Change it hot at 10,000 miles". I agree that this may not be applicable to cars used for a lot of short trips.

P E H

Justin,

I would recommend that you not do this. I just made the switch on my higher mile car and I now have several oil leaks I never had before. This wouldn't be so bad, except that I have already replaced the lower oil Pan gasket twice to get it right, and the engine is still leaking at the upper oil pan gasket which is very difficult to do in your own garage. If I could go back I would not do it again.

Just stick with, "Change it Hot, and change it often." rule and you will be just fine.

Good Luck

While I wish I could agree with Primo's comments, I can't.

All lubricants have improved, but synthetics are so superior in every respect (except cost) that they should be used whenever possible. I can't think of any exceptions.

I do generally agree that deteriorated seals are likely to let lower viscocity, slicker lubricant seep past. That said, I feel, as some writers have offered, that the superior qualities of synthetics may, in some cases, actually cause seals to swell and start maintaining a better seal. This however, is a marginal issue in most cases. Another easy answer - try a crankcase, transmission, or differential full of synthetic for about 5000 miles and see.

Changing it "hot and often" is an excellent battle cry, but one should at least use the best products available.

I will summarize in an even more binary fashion - there is no conventional lubricant that lubricates as well as its appropriate synthetic counterpart. Read the studies, ask the experts.

Let the conventional oil go the way of things like bias ply tires.

George

Right on George!
P E H

So is it safe to assume that (long term) the benefits of synthetic oil outweigh the possibility of leaks? Fixing a leak is less expensive than a new engine, I suppose. I did my last oil change about 1 week ago, so I have almost three months to make a choice. If I were to go synthetic, what viscosity should I use? The car has been given 15-40 since day one.
Justin

If you use the car in 30F degrees and up use 20W50. If car is used below 30F use 5W50. Castrol Syntec is the only maker of 5W50 , I think. P E H

Brother of The Benz,Justin Morrison
Reaping the benefits of Synthetic oils won't occur overnight.
There are varnishes, carbon and sludge deposits that have been aquired over the miles and the synthetics cleaning and detergent capabilities take time to remove this crude.
I was a diehard to changing to the man made oil.
At 150,000 miles the change was made.
My 103983 engine in my 1987 300E had never gone more than 4000 miles between changes using dino oil.
My engine didn't need the time to clean some of the left behind stuff.
Now at 177,000 miles, there are NO oil leaks and NO oil consumption.
Those who experience these problems must have been holding their engines together with stuff.
Justin, make your change to 20W50, set your intervals at no more than 5000 miles(filter too), get a pump to change from the topside.
Look at http://home.earthlink.net/~asherson/Don and save yourself some moola.
Happy Trails Beep Beep from The Spiderman in Houston!!!

I made the switch at 80,000 miles to Mobil 1. Sure enough, I developed a slight oil leak, which really irritated me since it hadn't had any before. For whatever reason ("blind hog finds accorn") I kept using Mobil 1. After about 10,000 miles the leak went away and stayed away. I use virtually no oil between 5000 mile changes, my car starts MUCH easier in below-zero weather, and my oil pressure is higher when idling in Midwestern summers stuck in traffic with the AC on.

I have read elsewhere that, in keeping with Mr. Swinford's (hope I spelled it right!) comments above that the superior detergent properties of synthetics SLOWLY dissolve years of accumulated gunk all over the engine, and that in some cases leaks develop temporarily since the rings may get "unstuck" from their grooves and actually increase blowby FOR A WHILE but then after the rings reseat themselves all is better than before.

Don't know if that's absolutely true, but I would say my mileage has increased from 20 mpg in town to 23 just recently, 20,000 miles after the switch . . .

__________________
Steve
'93 400E

At 125k miles, I changed to synthetics in a 1983 300CD. No leaks appeared, but some 10k later I got a leak in couldn't find the source of. It turned out to be the oil pressure guage at the fitting on the instrument panel. Mean while I had oil dripping on my accelerator pedal and soaking the interior carpeting. Man was I mad. Car was sold some 120k later and still running strong. If you believe in the discussions of synthetic oils you can substitute synthetic Redline 10-30 for dino 15-40. I personally wouldn't run the synthetic 5-50 because of the increase of polymeric thickeners used for the wide range of weights by some synthetic manufacturers. Either search this site or go to http://www.redlineoil.com/whyredline.htm

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Roger
1983 300CD 246k sold
1998 C230 52k
1980 450SL 75k needs AC
1999 Subaru Outback Ltd 43k

I personally haven't had any problems switching to a synthetic oil on a used vehicle.

At about 50k miles, I began using synthetic oil in my VW Jetta TDI. It now is pushing 200k and still doesn't leak or use oil. Also switched oils in my Cadillac V8 at around 90k. It now has 110k with no adverse effects. The MB started using synthetic in 1994 and 100k later, has not experienced any problems oil-related.

One word of advice though, if you plan on running extended intervals, it wouldn't be a bad idea to use a diesel-rated synthetic. Not so much an issue if you change at 3-5k miles, but if you are going to use a 10k mile interval, the diesel synthetic will handle the soot load better. I've done oil analysis both ways and there really a clear difference.

Keep us up to date!

__________________
Lance Allison
Lance@LanceAllison.com

Current:
11 MB S550 4Matic, 55k miles, Designo Black/Black
14 Ford F150 XLT Lariat Crew, 73k miles, 5.0
Coyote V8 4x4. Black/tan.
09 GMC Envoy Denali, 5.3 V8, 4x4 SWB. 38k miles,
Jewel Red/Med Gray.

Gone:
87 MB 300SDL, 320k miles, Astral Silver/Blue.
98 VW Jetta TDI, 488k miles, Classic Green/Gray.
85 Olds 98 Brougham FWD, 4.3 DIESEL V6, 80k
miles, 3x Gray.

MBCA Member, Chicago Region