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Discussion Starter #1
As some might be aware I only got my SLK320 a couple of weeks ago and since that time I have been asking around what lub oil should be used in a 2001. One MB dealer I contacted indicated 0W40 oil Synthetic another said that they now recommend 5W40 Synthetic OR regular 5W40. My wifes CX7 also uses 5W30 and I understand what the 5W is for the engine is turbo charge and in the winter months up north it help in starting. As I am never going to run my SLK320 after the end of October why would I need 5W40 oil. As we know once the engine is up to temp we are basically running a strait 40 oil. And why a synthetic oil? Sure it lasts longer but surely a good 10W30 or 5W30 would work fine for a car that runs only in the summer months.

Can someone explain the oil to me and what are most owners of a 170 SLK using in thier cars.F):Beer:R)
 

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See the manual.

Use whatever Mama Benz says to use for your model. They are smart enough to design and produce the car; I bet they are smart enough to recommend the correct oil for it.

dlomshek
Southeast, Kansas
 

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Sorry, can't explain oil. Since I bought my 230 SLK I have fed it a steady diet of 10W-40 Mobil 1 oil. I live in Phoenix so rarely see cold temps. I personally think the builders recommend the light oil viscosity to improve gas mileage. I usually get 25mpg overall and that's enough for me. I give her a steady diet of Shell 91 octane with an occasional Techron chaser and at 113k miles it's a great car. Using Mobil 1 also has the benefit of yearly oil changes. Phoenix is so easy on cars because we don't run engines in the cold.
 

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Oil weight must match climate conditions. 10W30 might be fine for Arizona, but I would think that 0W40 would be the best choice for Canada. You can find a temp vs. weight chart very easily.

MB Felt that it was worth the extra money to use synthetic as the factory fill, so that's good enough for me. Oil, even synthetic oil is cheap. Engines are expen$ive. Your choice.

If you are not going to use synthetic, do not use an oil in these small engines with more than a 25 spread between hot and cold viscosity. With Dino oil they have to use a very high quantity of Viscosity Index Improver(VII) additive to achieve that wide spread. The inordinately high volume of this additive is known to cause coking (carbon buildup.)

Modern engine oil blends are not simple. Things like the correct volume of VII for the engine and conditions are important. For this reason, you are typically better served to listen to the manufacturer rather than try to out think them.
 

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By far the most common oil used among SLK drivers based on numerous forums and thread discusssions is Mobile 1 0W-40 synthetic oil. Do yourself a favor and never use non-synthetic oil in the SLK, I can't find the links at the moment but the higher temps and compression in the SLK engine require the advanced heat and shear qualities of synthetic oil. A web site
http://www.bobistheoilguy.com/effects-of-shearing/
has good insights on shear forces in engines and synthetic oil's ability to handle them without the drawbacks of as many engine oil additives as non-synthetic oils use.

Half-way down this page the section

Drawbacks of Viscosity Improving additives

http://www.upmpg.com/tech_articles/motoroil_viscosity/
discusses viscosity additives in more detail, while following sections also talk about the quality differences between different grades of synthetic oil, which ties into why nearly everyone uses and MB specs its engines for Mobil 1 synthetic versus using some other synthetic brand name 0w-40.

For the oil weight, the 0W- portion also refers to the cold start-up protection until the oil is fully heated, it is not just your outdoor temperature, so there is no reason not to use 0W-40 regardless of your outdoor temps. Canada isn't known for 100+ temps, while tons of SoCal SLKers who have researched thoroughly use 0W-40 year-round into the 100+ degree non-coastal summer temps. The internal engine temps being generated aren't especially impacted by the modest summer temps in Ontario; the oil weight can play a role in the amount of sludge developed based on shear forces inside the engine relating back to the links above. A xW-30 oil simply doesn't have enough protection for the SLK engine temps.

The SLK makes extensive use of alloys, even seal materials like in the hydraulic systems break-down/degrade depending on fluid used, it isn't just tried and true basic automotive materials, so from power steering fluid to especially the coolant system, buy the Benz fluids, don't try to second guess and save a few bucks with basic-automotive axioms that such-and-such is just as good as the dealer fluid and it doesn't matter. The SLK is over-engineered and you'll reduce its lifespan significantly, or increase your maintenance repair costs radically, without proper spec fluids.
 

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Discussion Starter #12
OK you convinced me :tu::tu:Mobile 1 0W 40 synthetic it is. Got the oil this morning and filter last week was going to do the change myself but the mechanic that does my other two cars says he’ll do the change for me for $10.00 it’ll cost me that just to get rid of the old oil and I stay clean.

Now do I understand right that the oil is good for 10,000 miles or is that Kms?

Thanks again for all the help deciding what should be used in these machines

You guys kick :butt: lol Y):Beer:
 

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OK you convinced me :tu::tu:Mobile 1 0W 40 synthetic it is. Got the oil this morning and filter last week was going to do the change myself but the mechanic that does my other two cars says he’ll do the change for me for $10.00 it’ll cost me that just to get rid of the old oil and I stay clean.

Now do I understand right that the oil is good for 10,000 miles or is that Kms?

Thanks again for all the help deciding what should be used in these machines

You guys kick :butt: lol Y):Beer:
There have been lots of discussions.
Basically it depends on your driving habits, climate, area. Under normal driving conditions MB sets interval to 10,000 miles between oil changes or 2 years if your drive ander 10k in these two years. If you like to race then probably it's more safe to do it more often, say 6k miles.
I used to do mine every 6,000-7,000 but this time I'm going to 10,000 and will compare it.
I remember Sokoloff told that there are special kits you can buy off the internet. $25 approx. and then you fill them with your old oil and send it to the testing lab, and they'll return the results to you. Sokoloff showed us his and after 7k miles or so the properties of the oil were the same as of the new one. :D
 

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Discussion Starter #14
That maybe true I spent 35 years working on cargo ship trading woldwide and in all those year never ever had to change out the engine oil complete never ever. The last one I was on before I retired off them and went teaching the ship was built in 1960 and went for scrap in 2006 and still have the original oil in the sump. Mind that said oil was added and a sample was taken and tested each month. Strait 30 oil so 10,000 miles will do me.

Thanks everyone it's a leaning curve for me.:rockon:
 

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...never ever had to change out the engine oil complete never ever...and still have the original oil in the sump...
Are you completely sure of this? I understood heavy duty and large marine diesel still require the oil to be changed as it becomes contaminated. The alternative would be complete overhaul more often than specified.
 

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Yes as stated I have never ever seen the oil completely changed out on large marine engines. I'm not talking little 2000/3000 KW engines (Pup engines) I'm talking the 10,000 to 100,000KW engines that hold 1000's of gallons of oil. They have Purifiers running 24/7 and filters fitted, some have lub oil Centrifuges fitted that are cleaned once a watch (every 4 hours).
We do on going maintenance year round. Each time we get to port we would pull a couple of units for overhaul, maybe a main, connecting rod or a crosshead bearing what ever needs inspecting for Lloyd’s and all ship do an annual 5 year dry-docking and any work out standing is done then. In other words the maintenance is ongoing each and every day. Hope this helps you understand what I was talking about gdb069.

I have know reason to make that up
..:tu:
 

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Reset the FSS and go by that. It will give you 10K or two years as it starts to count down. You can always check it to see how much you have left. As for an oil analysis, the price is only about $15 a pop.
 
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Yes as stated I have never ever seen the oil completely changed out on large marine engines. I'm not talking little 2000/3000 KW engines (Pup engines) I'm talking the 10,000 to 100,000KW engines that hold 1000's of gallons of oil. They have Purifiers running 24/7 and filters fitted, some have lub oil Centrifuges fitted that are cleaned once a watch (every 4 hours).
We do on going maintenance year round. Each time we get to port we would pull a couple of units for overhaul, maybe a main, connecting rod or a crosshead bearing what ever needs inspecting for Lloyd’s and all ship do an annual 5 year dry-docking and any work out standing is done then. In other words the maintenance is ongoing each and every day. Hope this helps you understand what I was talking about gdb069.

I have know reason to make that up
..:tu:

I don't think Mercedes 320's and 350's have purifiers and centrifuges built into their engines -cleaned every 4 hours.
Why can't they fit these items to their engines?:burnout:
In SA our summer temps can go to +40C and where we are is never very often below 6C on a cold winter morning.

I have a hoist at my factory and change my engine oils at 5000km.
IMO this is the cheapest engine insurance that you can buy.
I use:
SLK 320 & 350. Castrol Magnatec Professional 5W40. (84000km), (105000km).
Boxster S. Elf ExcelliumSM 5w40. (161000km)
Jag XJ40. Castrol edge sport. 25w50. (265000km). Changed at every 10000km as is not really a performance engine.
 

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There have been some studies done that show that changing the oil too often is not helpful. Car engines are designed to use up the additive package in oil and not have heavy concentrations of it all the time. Whether you believe those studies or not is another thing. I do believe in the lab's oil analysis results that tell me that my oil is still good to go even at 10,000 miles.
 
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