I'm trying to decide if I should change my oil from a 5w30 to a 10w40.
I know I may lose a little bit on mpg (but then again by how much?).
However, is using 10w40 much better in the long term for the engine (+150,000 miles) ?...I intend to keep my car for a long while.
And by the way, the oil in question would be Redline or Amsoil.

Thanks for any feedback!

 

I'm curious, why do you think 5w30 would not be a good long term choice?

 

Not that it wouldn't be a good choice (especially with a quality oil), but I'm thinking a thicker oil might be better on wear and tear...

 

Personally I would go with a good oil at or close to the factory spec weight.

 

Here is what BMW TIS Service has to say. One shouldn't be suprised that BMW may actually know what they're talking about when they publish their oil recommendation:

4.0 Viscosity Grades
Viscosity measures the oil's ability to flow. It is highly dependent on the temperature of the oil, ie. the higher the temperature, the lower the viscosity. Likewise, the oil temperature is dependent on various factors, for example on the ambient temperature in which the vehicle is operated.
When the outside temperature is low, the oil must not be too viscous, so as to ensure that all the lubrication points are supplied quickly with oil when the engine is cold. When oil or engine temperatures are high, the oil must possess a certain minimum viscosity, so that an adequately thick lubricating film is built up.
Modern multigrade oils combine good low-temperature characteristics with adequate lubrication at high oil temperatures, preventing the need for a suitable viscosity grade to be selected and oil to be changed purely on a seasonal basis.

BMW Longlife Oils:
BMW longlife oils, as specified for all BMW vehicles since 1998, are tested by BMW to ensure that they can be used anywhere in the world, at any time of the year, regardless of ambient temperature. If BMW longlife oils are used, it is therefore not necessary to keep a check on the viscosity grade. BMW longlife oils are only available in viscosity grades SAE 0W-30, SAE 0W-40, SAE 5W-30, and SAE 5W-40.

BMW Special Oils:
This oil standard has been approved by BMW for viscosity grades SAE OW-X, SAE 5W-X, and SAE 10W-X (where X stands for 30, 40, 50, or 60). SAE 0W-X and SAE 5W-X oils can be used anywhere in the world, at any time of the year, regardless of ambient temperature. For SAE 10W-X oils there is a lower temperature limit of -20 degrees Celcius. Cold-starting difficulties may occur at lower temperatures.

ACEA Specifications:
The most suitable viscocity grade should be selected when using the viscosity/temperature diagram. Here again, making the right choice will avoid the need for purely seasonal oil changes (eg. SAE 15W-40 for central Europe). The temperature limits shown in the diagram may be exceeded for a short time. If the upper temperature limit is exceeded, high engine speeds and loads over a prolonged period should be avoided. If the lower temperature limit is exceeded, difficulties may be experienced in starting a cold engine.


Though it is unlike me, I won't go into the criteria for BMW's oil selection, but I will list the factors they based their oil recommendation on (which by the way is MINI SYNTHETIC OIL 5W-30 p/n 07 51 0 143 829):
High level of protection against wear and reduction of friction.
Favorable viscosity/temperature characteristics.
High residue-scavenging, cleaning, and neutralising
capability (good dispersant/detergent effect).
High thermal stability.
High oxidation and ageing stability.
Slight tendency to vaporize.
Favorable foaming characteristics.
High level of protection against corrosion.
Unproblematic mixability/compatibility.
High thermal conductivity / good cooling capability.
Restricted tendency to form combustion residues.
Long shelf life.



If you care to read on, here is some info from BMW shop/training manual "History and Introduction to the MINI" about the oil delivery system on the Cooper S:

Oil Circuit
Oil is drawn up through the oil strainer to the oil pump, which is located at the front of the engine: the oil pump delivers oil under pressure through the full flow oil filter to the main oil gallery.
The main oil gallery also supplies oil to the cylinder head assembly via a verticle hole on the exhaust side of the cylinder block between bores two and three. The cylinder head gasket incorporates an oil restrictor to ensure that oil volume to the crankshaft is maintained and oil volume to the cylinder head is reduced.
The upper engine lubrication is provided by one main feed to the number three camshaft bearing cap. Oil is then routed through the rocker shafts to the remaining camshaft bearing caps and rocker arms/hydraulic lifters. Oil returning to the sump pan from the pressurized components supplies lubrication to the valve stems.

Piston Cooling
The MINI Cooper S incorporates oil "squirt" jets to assist in the cooling of the piston crown. The four jets are located in the cylinder block next to the main oil gallery. Oil spray is controlled by a ball and spring. These allow oil flow only when the oil pressure exeeds 2 bar. The position of each jet is critical to the effectiveness of the cooling.

Oil Pump
The oil pump and pressure relief valve are located on the front cover (internally) and are secured by 10 bolts. They are both manufactured from aluminum.
The oil pump consists of two gears. The internal gear is driven drectly from two flats on the crankshaft nose and is in permanent mesh with the outer gear.
The eccentric rotation of the gears creates a low pressure at the inlet suction crescent end of the pump and draws in oil. As the gearwheel rotates, oil will be compressed between the gears and discharged at the outer port end of the crescent at a high pressure.

Oil Pressure Regulator
The oil pressure relief valve is installed in the oil pump housing. The valve consists of a spring, retaining cap, circlip, and a hollow plunger with radial holes.
If a blockage or restriction occurs and the oil pressure is sufficient to overcome the spring tension, the plunger will force back, exposing the radial holes and oil will return to the low pressure side of the pump.

Oil Filter Housing
The oil filter housing is located adjacent to the exhaust manifold and is externally mounted by three bolts. The housing incorporates a spring-loaded drain back function, allowing oil to return to the oil pan. The drain back function is activated as the oil filter top housing is unscrewed.
The oil filter housing also retains a bypass valve for the full flow oil filter and an oil pressure switch. The oil filter is a disposable paper element and is retained in the upper section of the aluminum housing.

 

5W30 fine on newer motor if your using a good syn. oil. Amsoil is good, Redline is better. On motor with 100K miles 10W 30 may be a better choice. I can see no reason to use 10W40 in a Mini (unless its a classic Mini).

 

I remember years ago Motorcyclist Magazine ran some tests on using higher than recommended vicousity oils. The thought at the time was a thicker oil would be better in the desert for example than a thinner oil.

The interesting point was the thicker oils actually ran considerably hotter than lower weight oils, which I think would indicate more friction. I'm not sure whether synthetics would show the same results.

 

Heavier oil is not better oil, it is just heavier. This means that it will take more time and horespower to make it flow through the engine. Since most engine wear takes place just after start up, the quicker oil gets flowing through the engine, the better. Back in the old days, when engines had much looser tolerances, we needed thick oil to take up the space between bearings, etc. With today's much closer tolerances, this is no longer needed. Your engine was designed for the oil that is specified by the manufacturer. Synthetic oil has a much higher "shear strength" than conventional oil, somewhere around 700 times the "shear strength". This is the ability for the oil to resist being squeazed out from between the parts it is supposed to protect. So synthetic oil is providing the additional protection you are seeking, using a higher viscosity will just cause additional wear because it will take longer to circulate.

Hope that helps.

 

Thanks for the feedback.

5W30 Redline it is then! (found some for $6.30/quart )

 

where?

 

Is there something wrong with Castrol Syntec? I thought this is what MINI's have from the factory. I'm asking because it was on sale at NAPA for about $4.50 a quart.

 

Just make sure it's pure synthetic, not a blend. Castrol likes to add "syn" to a lot of it's oils making people think it's a full synthetic when it's really only partially synthetic. The MINI needs full synthetic.

 

Thanks - the napa dude explained that also so I did get the full synthetic. I'm going to be changing oil a lot more often than recommended so I want a good synthetic that also doesn't cost an arm and a leg!

 

Sure. If you are putting it in a '58 DeSoto.

People often equate thick oil with longer engine life. Today's modern oils are able to provide extraordinary wear protection compared to what was available less than 20 years ago. Engines today are made with tighter tolerances and smaller clearances in order to perform better and more economically as well as to lower emissions. These engines also run hotter than old-school designs simply because they are making more power with less displacement and in a smaller space. because of all this, oil has to be able to not only reduce friction but also flow quickly to help dissipate this additional heat.

Oil being subjected to typical forces in an engine generates heat as the oil film is sheared and twisted. It's simple physics. One way to reduce this is to make the oil thinner. Back in the day making the oil thinner made it less effective. Today's synthetic oils are incredibly effective even when water-thin. Thick oil does not flow quickly through various engine parts. The longer it stays there without being pumped through, the hotter it gets. This heat is passed onto the engine components, which are also being heated by the combustion processes and friction. Net result: even hotter engine components.

Another issue that crops up is oil pressure. Thick oil is harder to pump. This causes extra work for the oil pump, and with that, more heat. High oil pressure does not mean less wear on your engine like it used to. You want the oil moving throughout the engine as fast as possible, carrying heat away from the components and circulating throughout the engine. Thick oil makes the pump run in bypass, running the oil round and round in the pump, generating more heat and breaking down the oil.

Stick with the recommended weights of oil. Use the highest quality synthetic oil you can buy. Your engine will thank you for it.

 

Thanks Greatbear. That's what I thought and what I'll do.
Just wanted to be 100% sure and therefor seek the counsel of this highly knowledgeable forum


VoiD,
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