Will switching to synthetic oil damage engine??

[Fidens]

So I just bought a '91 300d, and the previous owners were quite meticulous about changing the oil every 3k miles. However, they always used Rotella T non-synthetic oil. I was going to switch to full synthetic on the next oil change, but while researching a few things, I came across this post in another forum:

"I reccomend you use whatever weight of oil that your manual indicates. The engineers at Mercedes intended these engines to use this oil, using synthetic substitutes on non-completly rebuilt engines usually causes more problems than anything. To be more specific, the synthetic oil acts like a solvent. Freeing years of built up oil deposits, deposits that prevent oil from leaking out of ancient gaskets. This more slippery oil, often slips its way past piston rings and past valve guides, past gaskets and makes what was a previously well running engine into a basket case."

Just curious what your take on it is. Has anyone had problems switching to full synthetic on older MB diesels? In my experience, I've never had any issues switching to synthetic oil, but previously it was always on gasoline vehicles with 30-80k miles on the clock... the situation may be different when dealing with a 20 year old diesel that has seen 180k miles.

[LandYaghtLover]

I dont think its an issue. While it can free up gunk, one could use an additive such as Seafoam before the change over. That way most of the gunk will end up in the old oil.

Also, 3K oil changes are not recommended or needed in a gaser, not sure about a tractor engine. But I would check up on that. Might be throwing $$ away.

[vstech]

if the Previous Owners of THAT car have been maintaining 3K oil changes, synthetic will not have anything to clean out... the motor will be sludge/varnish free. synthetic will only improve starting and longevity of the motor.
be sure and use TDT M1 or Amsoil or Lubrimolly full type IV full synthetic CJ4 rated 5W40 oil.

[Marvelicious]

Sounds like a real Luddite to me. My 82 likes it just fine. Synthetic can find its way through spots dino cannot; but first: anything it leaks past should probably be replaced anyway, and second: I've never heard of any leaks developing that didn't dry up again if switched back to dino.

I guess I can see his sludge argument on some old beater that hasn't had regular oil changes and you're just trying to get as many miles as you can for the least money, but anything that has been properly maintained, I just don't buy it.

[tram]

I only use Castrol Syntec 5W-50 in all my vehicles. My wife's '85 300TDT got switched from the previous owner's Rotella at 175K and 10 years ago. Now 300K and no issues.

[Zacharias]

Originally Posted by Fidens

"I reccomend you use whatever weight of oil that your manual indicates. The engineers at Mercedes intended these engines to use this oil, using synthetic substitutes on non-completly rebuilt engines usually causes more problems than anything. To be more specific, the synthetic oil acts like a solvent. Freeing years of built up oil deposits, deposits that prevent oil from leaking out of ancient gaskets. This more slippery oil, often slips its way past piston rings and past valve guides, past gaskets and makes what was a previously well running engine into a basket case."

That is old and outdated opinion. It reflects the state of the technology about 15-20 years ago.

As has already been said, just make sure you use an appropriate synthetic oil.

[shertex]

I've made the switch on two of your exact same car with no problems whatsoever (albeit at somewhat lower mileages). Especially since it's been well maintained, you should have no issues.

If you're a miser like I am....you can get the one-gallon jugs of Mobil 1 Turbo Diesel Truck 5W40 at Walmart for about $24. Not every Walmart has it all the time....so good to stock up.

Also, please note that there is a MISTAKE in the oil capacity given in the manual for the 91 300D. It says 7.9 qts., but it should say 7.5 qts....this was corrected in a TSB and later manuals.

Since I check my oil level regularly, what I do is add an even 7 qts. which puts the oil level about midway on the dipstick marking. Some people have found that, if they add the full 7.5 qts., a half qt. or so keeps burning away. Lots of threads on this issues.

Enjoy your new car and welcome to the forum!

[DeliveryValve]

Originally Posted by tram

I only use Castrol Syntec 5W-50 in all my vehicles. My wife's '85 300TDT got switched from the previous owner's Rotella at 175K and 10 years ago. Now 300K and no issues.

Castrol Syntec 5W-50 is not diesel rated.

I am not a fan of it, I used to use that oil in my Toyota for the first 90,000 miles of it's life. Opened up the engine when timing belt, and the engine was full of varnish inside. Very disappointing. I then switch to Mobil 1. Timing belt is coming up soon again, well see what the results are.


.

Originally Posted by shertex

....
If you're a miser like I am....you can get the one-gallon jugs of Mobil 1 Turbo Diesel Truck 5W40 at Walmart for about $24. Not every Walmart has it all the time....so good to stock up....

I just recently purchased M1 TDT 5w40 from Wallyworld. Price is over $26.
But still cheaper then O'Reilly's at $29.99.









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[raysorenson]

Originally Posted by Zacharias

That is old and outdated opinion. It reflects the state of the technology about 15-20 years ago.

Yes, maybe even older. I trace it back to the addition of detergents in motor oil. Lots of folks claimed that an engine that used older non-detergent oil would get damaged by oils with detergents because it would break up deposits and send them circulating throughout the engine. While this has a little basis in fact, millions of cars switched over without a hitch. Somehow people have transplanted this argument over to synthetics which have detergents just like all other motor oils these days.

[charmalu]

I changed the 80 240 to synthetic at 321K, and am at 327K w/o any issues.

I have made 2 trips to Portland, Or. (about 730mi one way) and one trip to Los Angeles (about 350mi one way). and 2 trips to northern Calif (about 275mi one way). so I have been pounding it on the freeway`s w/o any Ill effect. first qt I added was at 1400mi.

This synthetic is just another old wives tale that keeps getting circulated around through another generation of car owners.

Charlie

[charmalu]

Originally Posted by charmalu

I changed the 80 240 to synthetic at 321K, and am at 327K w/o any issues.

I have made 2 trips to Portland, Or. (about 730mi one way) and one trip to Los Angeles (about 350mi one way). and 2 trips to northern Calif (about 275mi one way). so I have been pounding it on the freeway`s w/o any Ill effect. first qt I added was at 1400mi.

This synthetic is just another old wives tale that keeps getting circulated around through another generation of car owners.

Charlie

I stumbled across the thread doing a search, posted the above on 10-25-11.
we are up to 367K miles and the 240 is still chugging right along. oil use is about the same, after the last change, I added a qt at 1700 miles. generally she is around 1200 - 1400 miles depending how she is driven. She is still staying dry, but do get a drip on the driveway every once in a while.

She isn`t a putz around town car, quite a few trips to Oregon and Nevada. since April 1 been to Carson City and back, 900 miles, Portland and back, 2100 miles, So Cal to a GTG and back 700+ miles. will probably put 300+ miles on Saturday to another GTG. Then back to Carson City on Monday for a one day run.

Charlie

[Zacharias]

Originally Posted by raysorenson

Yes, maybe even older. I trace it back to the addition of detergents in motor oil. Lots of folks claimed that an engine that used older non-detergent oil would get damaged by oils with detergents because it would break up deposits and send them circulating throughout the engine.

Well now you made me feel old.

I actually remember a mechanic going on about that very point to me, many moons ago, when I asked about oil for my first Volvo.

[Stretch]

Yeeee ha! An oil thread!

(Welcome to the forum Fidens)

[layback40]

Originally Posted by Army

Yeeee ha! An oil thread!

(Welcome to the forum Fidens)

You beat me to it Army !!!

I think we need a sub-forum for "oil" threads.

There appear to still be plenty of snakes in the world & people trying to squeeze oil out of them.

"Oils Is Oils" !!!! Get used to it.

The magic foo foo juice additives are mainly marketing hype.
Buy a well known good quality oil rated for your car & be done with it.

The molecules in the oil dont know their parentage, if they came from a refinery or a petrochemical plant ~ they use crude as feed stock anyway.

Have a look in your owners manual (that little book in your glove box that you should have read when you first got your car) about what the oil specification for your car is.

[andrewjtx]

Are we allowed to post the "Aww, not this ^&*( again." picture?