Changing oil type: dino to synthetic
 

I have a 1992 300 TE wagon with 132K miles on it. I don't know what type of oil was used previously. Suprisingly this car has virtually not oil leaks or even seepage. I say suprisingly becasue I have another 1992 300 E sedan with 126K miles on it and it does have some oil seeping. I changed to synthetic oil Mobil 1 15W-50 in the sedan at 60K miles.

I'm just wondering if under the circumstance it would be best for me to just use dino in the wagon.

Below is some information I got from checking this topic.

From what I've read, the synthetic oil can remove deposits left by the natural oil. The concern is these deposits may be blocking leaks. So by switching, you end up leaking oil. Some people mistakenly blame the oil for causing the leaks.


Switching to synthetic on a high mileage car? You may or may not have problems with leaks. Gasket and seal material has gotten better lately and the detergent properties of good synthetics are not as harsh as they used to be. It all depends on how much the sludge in your engine is acting as a seal for the oil.

Not a viscosity issue WRT leaks. Synthetic oil has more detergent properties. It will remove the sludge that is plugging the leaks.

I have done it on a 20 year engine with 200k miles that has never been opened, rebuilt or resealed in any way. Never caused a problem. I also started using it in my C280 at 60k miles. Now has 145k miles and still doesn't leak a drop.

I have a '94 C280 with about 90K miles on it, and there is a minor leak on the head gasket that I'm monitoring. I'm keeping with the dino oil as opposed to switching to synth for the very reason you mentioned. If my motor was visibly dry I would make the switch.

There are NOTHING but "old wives tales" etc. speaking against using synthetic oil. None of it is real.

Just do it.

I agree.

I'm sorry you feel that way. Having done about 10,000 oil changes in my lifetime, and having seen this very thing happen first hand, I have a different opinion. Not a chance I'm prepared to take on my car, but by all means if you're comfortable do it on yours.

Well having done about 10,001 oil changes in my life time including 4 years of municipal car fleat service, I have never seen this happen. But I did enjoy running my 93 Taurus 220,000 miles at 8500 mile change intervals. It's still going. I'v just witched over the 560SL at about 105,000 miles to Mobil 1 after replacing the head gasket, which was leaking oil. Maybe it was the regular oil that caused the leak.

John Roncallo

From what I've read here and elsewhere, apparently the early synthetics back in the '70s lacked additives to swell the seals. So seals shrunk over time, the synthetic oil helped clean out gunk, and the "thinner" synthetics slipped out . . . thus the notion that "synthetics cause leaks on older cars used to conventional oil."

Nowadays, all the synthetics have seal conditioners to control exactly this scenario.

I disagree with you somewhat. Years ago I had a 1948 Chevy pickup. The guy that had it before me only used non-detergent oil. The first time I changed oil I used a modern oil and the engine started leaking like a sieve. Before I changed oil the engine didn't have a single leak. So I would think that if the synthetic has stronger detergents that leaks could develop on older engines.

I just switched over to fully synthetic oil in my diesel I have nearly 287K miles on the original engine, and its entire life has been run on the regular stuff. After about 1K miles, the oil finally turned black, and I plan to change it at 4K miles. No leaks anywhere. I love it.

Syn oils have better cleaning properties except for maybe diesel specific oils and is generally a finer oil.

In my opinion, if you have leaks or just about to, the syn oil will find them for you by cleaning your engine.

Haasman

I'm very much inclined to stay with dino oils with this 300 TE. Interestingly my local MB dealer said the recommended oil for this car is Mobil Delvac 1300 in 15W 40. That is what they use at the dealer, even though that is an oil for diesel motors. Don't that seem strange?

Ron,

What viscosity does your book call for? I have only had diesel MBs ... 15w-40 sounds a bit thick for a modern gasoline engine ...

Regarding whether one should change to synthetic - this is easy one - of course you should, if you want the best lubricant with minor added cost. Synthetics are better in every way except price per mile - they do allow increased change intervals, but that isn't the best reason to use syn - the best reason is that it is simply better than dyno - in every technical respect.

Syn v. Dino
 

I changed my 420SEL to Mobil 1 after purchase @ 145,000 miles; no leaks in two years; I have no idea what was used previously. I think the syn may be too good for the easy service my car sees, but it makes me feel better, anyway. I change it annually (probably less than 2500 miles per year).
To each his own.

Delvac 1300 15W-40 is a great oil for the M103. I ran it over the summer and would run it year round if it never got below 15-20 degrees F. For the cold temps I've moved to Delvac 1 and seen no leaks caused by it.