Dumb question but where in manual does it say 0w40 oil for the c43? i cant find it!
Member
Joined: Apr 2012
Posts: 178
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From: So California
1999 C43
I live where it's 115 degrees in the summer; I use 20w-50 Mobil1 year round. If I were in a more temperate climate. I would go to 10w-40 or 0w-40 if it's below freezing in the winter. I worked for a major oil company for 20 years and a big V-8 can handle a heavier oil especially with some mileage on it.
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Joined: Apr 2005
Posts: 3,784
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From: SCV SoCal
2002 CLK430
Trust me, this really isn’t rocket science
Every now and then the subject of oil comes up. I choose to base my choices on the facts published by (1) the engine designer and (2) the motor oil vendor.
When motor oil reaches 212 degrees Fahrenheit, it’s at the minimum end of the normal operating temperature range. In addition, oil flow at operating temperature (212F) isn’t the issue. The majority of oil related engine wear occurs during cold starts. That’s because of a lack of lubrication and lubrication is dependent on flow. Viscosity, as it's measured in motor oil, is a measure of a fluid's resistance to flow, or it's "thickness". That "thickness" is quantified in centiStokes (cSt), which is temperature dependent. If you want to cross check this, Google "Stokes Law" and "viscosity". This may be why Mercedes-Benz publishes the cSt ratings of their approved motor oils. Exxon-Mobil also publishes the cSt ratings of their oils at two industry standard temperatures - so this is going to be very easy.
At 212 degrees Fahrenheit, Mobil1 0W-40 is 14cSt. At the same temperature, Mobil1 5W-40 is 14.8 cSt and Mobil1 10W-40 is 14.7 cSt. Yes, they are all about the same. That’s why I said flow isn't an issue at normal operating temps.
Cold is a different story. Suppose your car is sitting outside on a 115 degree day. For the sake of argument, lets say your "cold" oil is 104 degrees Fahrenheit - it isn't, but lets use that number. At 104 degrees Fahrenheit Mobil1 0W-40 is 78.3 cSt. This is way too thick and why there is excessive wear during a ‘cold’ start. But wait, there’s more - Mobil1 5W-40 is 102 cSt - I don’t have a Mobil1 product data sheet for 20W-50, but Mobil1 15W-50 is 125 cSt. I think we can agree that a 20W-50 weight is probably thicker than a 15W-50 weight on cold start up, so this isn't going to get better. Especially when a "real" cold start occurs (like something below 30F) and the oil is much thicker.
BTW, when an engine designer choses bearing clearances, they do it based on expected oil flow. Obviously, an oil that is 78 cSt is going to do a better job during warm up than one that is 60% thicker.
That said, I think everyone should use whatever they feel comfortable with. I'm just stating a couple of reasons why I choose to use 0W-40. If I've overlooked something feel free to point it out. I've had two Mobil1 data sheets listed here for about a decade. Mobil1 lists the 15W-40 data sheet here.
When motor oil reaches 212 degrees Fahrenheit, it’s at the minimum end of the normal operating temperature range. In addition, oil flow at operating temperature (212F) isn’t the issue. The majority of oil related engine wear occurs during cold starts. That’s because of a lack of lubrication and lubrication is dependent on flow. Viscosity, as it's measured in motor oil, is a measure of a fluid's resistance to flow, or it's "thickness". That "thickness" is quantified in centiStokes (cSt), which is temperature dependent. If you want to cross check this, Google "Stokes Law" and "viscosity". This may be why Mercedes-Benz publishes the cSt ratings of their approved motor oils. Exxon-Mobil also publishes the cSt ratings of their oils at two industry standard temperatures - so this is going to be very easy.
At 212 degrees Fahrenheit, Mobil1 0W-40 is 14cSt. At the same temperature, Mobil1 5W-40 is 14.8 cSt and Mobil1 10W-40 is 14.7 cSt. Yes, they are all about the same. That’s why I said flow isn't an issue at normal operating temps.
Cold is a different story. Suppose your car is sitting outside on a 115 degree day. For the sake of argument, lets say your "cold" oil is 104 degrees Fahrenheit - it isn't, but lets use that number. At 104 degrees Fahrenheit Mobil1 0W-40 is 78.3 cSt. This is way too thick and why there is excessive wear during a ‘cold’ start. But wait, there’s more - Mobil1 5W-40 is 102 cSt - I don’t have a Mobil1 product data sheet for 20W-50, but Mobil1 15W-50 is 125 cSt. I think we can agree that a 20W-50 weight is probably thicker than a 15W-50 weight on cold start up, so this isn't going to get better. Especially when a "real" cold start occurs (like something below 30F) and the oil is much thicker.
BTW, when an engine designer choses bearing clearances, they do it based on expected oil flow. Obviously, an oil that is 78 cSt is going to do a better job during warm up than one that is 60% thicker.
That said, I think everyone should use whatever they feel comfortable with. I'm just stating a couple of reasons why I choose to use 0W-40. If I've overlooked something feel free to point it out. I've had two Mobil1 data sheets listed here for about a decade. Mobil1 lists the 15W-40 data sheet here.
