Which Oil?

The answer will vary from person to person here, too.

I use the very high quality Mobil1 5W50 in every car. Others will tell you to use any other random oil. Your choice - your pain choosing. BTW: BMW recommends Castrol.

Your choice of oil may be determined by the mileage and condition of the car and what you expect from it. When it was designed, Mineral oils were the norm and typically oil change intervals were once a year or every 10,000 miles. Nowadays, upto 20,000 miles can be covered in between oil services but this is through the use of fully synthetic oils.

A 10W-40 mineral oil, such as Castrol Magnatec would be perfectly Ok, but if you intend to keep your car for many years then probably a good synthetic would give you better protection for the long run and under severe conditions. I use Mobil-1 0w40, but the 5w50 mentioned is also a good choice and there are many other oils to choose from as well. The lower the first number, the better the oil will flow when cold and this reduces wear on cold engine starts (where most of it occurs). The second number (after the 'W') gives the viscosity of the oil at operating temperature, about 100C. Thicker oils are less likely to sheer under heavy load, but the minimum HTSH number required by BMW is 3.5 and this is met by Mobil-1 0W40.

Castrol also makes synthetics, but with them it's harder to tell whether or not its a true synthetic or even part-synthetic.

Offiicially, the 10W-40 is the recommended oil, but that was based on the standards of 10 years ago and so you should not necessarily use that oil. As mentioned BMW is now tied to castrol so that would now be their 10W-40 MAGNATEC, which AFAIK is not synthetic based.

I've used Mobil 1 0-40w in my two 5's and now in my 8, expensive but worth every penny !

My 840 (M62) got from the BMW dealer in her first life original BMW 0W30 full synthetic.

I rather chose Mobil1 0W40, and have (obviously ) zero oil consumption.
I agree, worth every cent of its price.

Zitat von freeman81;68720

Many thanks for all your replies!

I do like the sound of the fully synthetics, why is it people say that it could make the engine sound 'tappety'?

Sorry if this is a dumb question!

Because it is so thin when up to operating temp,I used it unsuccessfully in my low mileage 840, ,worst of all the car suffered horrendous oil leaks so I drained £70 worth of oil & refilled with a better suited oil to the engine ie semi synthetic & all was well instantly, just MHO of course

switching from mineral to synthetic will result in a temporary cleaning-phase. That is, if you use high quality synthetic oil.

What happens is that clogged up parts will get cleaned by the new oil. This leads to temporary (let's say about 300miles) smoke (if badly clogged previously) and oil consumption. After these 300 miles, the engine will be cleaner and smoke and oil consuption will go back to normal.

If you have used mineral oil for some time, consider a proper engine cleaning with motor clean from liquy moly (as an example) prior to your oil change. I have excellent results with it.

Just remember: nobody here nor anybody else you will ask has an objective opinion on the matter (with the exception of the experts at BMW motor construction and the motor oil company research depts). Choosing your oil is more the result of religious-like belief than experience. Simply because nobody can ever say that he has ruined an engine because of poor oil and has an exact engine still in excellent condition using great oil. there are no real comparisons that were done by ordinary people like the ones here on the forum. period. Oil quality today is just very good across the board.

OIL

Fuzz is right.....but try this....

1. Pour yourself a nice cold beer
2. Type OIL in the search box
3. Sit back and read all the threads on the subject.

It is actually a religious experience.....the science of modern oils is quite staggering

Oh...and

4. Never, never, never use additives like Slick50 as they are a complete waste of money.

However, there are certain additives guys can recommend for high mileage engines....but that's another 4 beers away....

Here in the UK where temperatures do not go too low, I would recommend a 10W40 or certainly no thinner than a 5W40. Anything thinner will encourage oil consumption and leaks. I feel 0W40 is too thin as is 5W30 for the summer months and high operating temperatures.

Synthetic or semi-synthetic is simply a matter of cost and longevity. I would rather use semi and change the oil every 10k than use fully synthetic and change at 20k. I use a 5W40 semi in my M62 engined 540i and have no problems, but I change it every 6k together with the filter.

In my CSi I use 10W60, changed every year (very low mileage) which covers the coldest UK winters and the wettest UK summers, (you know, warm rain instead of cold rain!) This was recommended by the R+D dept of Castrol before I did a trip through the US during the summer months. But at the end of the day, a CSi is a SOHC, 2 valve, 20 year old dinosaur.

As previously stated, everyone has their favourites and you would not go far wrong using good ole Magnatec for Advanced Engines.

8Tech.

Many of you guys remember my struggle with the oil situation but in the end I decided to go with the Castrol Mineral Oil as it has always used. It works great on that oil and untill I wont open the engine it wont run on anything else. The reason is that it has always used mineral oil

like previously stated.
Ask 10 people and you will get 10 answers.

I just changed the oil on my 850 and I used Castrol 10W60 racing, and run the car for 8-10.000km between oil changes.

But instead of talking about what I do, lets just go through som basics.

1. change the oil frequent, not every 20-30.000km, oil also picks up humidity, degrading the oil over time, so change at a set mileage or time interval, whichever comes first.
2.the 0/5/10/15W number indicates the cold viscosity of the oil, the lower the number the thinner the oil.
3. using 0W oil on an old engine could give you oil sweating, and the engine may use oil.
4. if what I stated in 3. happens, just use a thicker oil, 5W or 10W.
5. Synthetic oils are usually 0W and 5W, som high performance oils may be 10W, mineral oils are usually 10W and 15W.
6. the term synthetic is in fact missleading as the oil is in no way synthetic, it is mineral oil that has been processed and added additives to make it better than plain mineral oil.

So it really does not matter what oil you use, just change it at regular intervals, and if it starts sweating just take it up a grade next time.

Zitat von Noggie;68781

...
3. using 0W oil on an old engine could give you oil sweating, and the engine may use oil......
6. the term synthetic is in fact missleading as the oil is in no way synthetic, it is mineral oil that has been processed and added additives to make it better than plain mineral oil.
......

By definition, a 10W-40 oil has the same viscocity (about 10cSt) at operating temperature (100C) as an 0W-40 oil. Therefore, if an engine doesn't consume oil with one type, it should not with the other either.

The first number defines the viscocity of the oil at 40C and at this temperature, the viscocity of either oil is between 5x and 10x greater than the viscocity at operating temperature (100c). So, if you engine does not use oil when it is warmed up, it certainly should not use any when the oil is cold and much thicker. A thinner oil at start-up is beneficial to start flowing quicker and protecting sooner, but note that any oil at start-up in a cold engine is greatly more viscous that it is at operating temperature. Therefore, I would say that the lower the number before the W, the better.

Synthetics have a much higher viscosity index than mineral oils. Consequently, they can operate as "multigrades" with a wide range, eg 0W-40; whereas, mineral oils need long-chain molecule additives to act as viscocity improvers to prevent the oil thinning too much at high temperatures. These long-chain molecules tend to sheer and break down over time, which is one reason why running on mineral oils requires more frequent oil changes.

Finally, the point in No.6 is what Castrol would have you believe for their lesser "synthetics". Yes, synthetics can now be made from highly refined Hydro-cracked mineral oils, but most PAO- based oils (eg Mobil-1) and ester-based (Castrol TWS?) oils are not derrived from mineral oils and this was the original definition of synthetic.

Castrol Magnatec is a mineral oil with a small amount of ester additives, which help the oil cling to the metal.

Aircraft engines (gas turbines) run on ester-based oils and not plain old mineral oils so go figure.... obviosuly synthetic oil must be better.

Zitat

Aircraft engines (gas turbines) run on ester-based oils and not plain old mineral oils so go figure.... obviosuly synthetic oil must be better.

Just to stress a further point on this ever growing thread

Yes synthetic Oils are better No one is disputing that BUT not for the 8 ?

Any decent engine builder will tell you that the tolerances in the V8 & basic V12 are no where near those of other high performance engines that DO require the very best Synthetic oils, so no need really to go & figure.

For example Alpina take the M62 V8 block & hone it to their own specifications Alpina recommend Castrol Synthetic but for the same unit that goes into the 840sport[ Not really a Jet fighter] Bmw Don't recommend synthetic .

That is my point;-)

Lets remeber that 20 years ago synthetic motor oil was not that common, and it was expencive.
Also as you say the M70 is very similar to the M20/M30 which basic design was designed back in the 60's... when I'm not sure syntetic oils even excisted, so it does not really need it. Synthetic oilsare better, because tey last longer before they break down, but using synthetic oil, and cahnging at mineral oil intervanls should keep your engine intop nitch for ages.

When the new BMW engines hit the marked, with vanos and 4 valve technology, the manuals state 0w or 5w oil to be used.

And I agree with Arnie, if you use the car during the winter, use a 0w or 5w oil, I dont, so I use the 10W oil.
I have seen M20, M50 and M52 engines sweat and burn oil when using 0w-30 oil, and not when using 5w-40.
Also there has been put alot of local effort into reducing BMW's tendecy have excessive valve tikking aftet track use, using a high quality Castrol oil like 10W-60 has proven to reduce this significantly.

As for jet engines those are dry sump lubricated.... I used to fix Boeing 737's for a living for 7 years, and F16 fightes for 3 years, so I know a bit about airplanes and turbine engines.

Zitat von stevep840;68797

....
Any decent engine builder will tell you that the tolerances in the V8 & basic V12 are no where near those of other high performance engines that DO require the very best Synthetic oils, so no need really to go & figure.....;-)

Yes, I agree, the tolerances on these old engines are far wider than on recent engines.... and there is nothing wrong with using the recommended mineral oil with the specified service interval.

The reason that these engines can run on an xW-50 or even an xW-60 oil is precisely because the gaps between moving parts are greater. My point is that with a mineral oil, you might get a 10W-40 or a 20W-50, but with a synthetic you can find grades such as a 5W-50 or a 10W-60 (as castrol TWS). These will give you better protection on cold starts and maintain a relatively thick oil film when the going gets tough. These kinds of oil were not available some years ago, but they are now and there's no reason to take advatage of them, particularly as 80% of wear really does occur during cold starts.

As an example, 2-3 years into production, BMW increased the tolerances on the V8, S62 engine such that 10W-60 oil could no longer be used as it was too thick, now requiring an 0W-30 oil. In such applications a synthetic is essential in order to maintain a sufficient oil film-strength with the very low running viscocity. However, the thinner oil provides lower friction losses and being synthetic has the same film strength of thicker mineral oil.

As I first said, I think its a question of what you expect from the car and how long you intend to keep it.

Ten years ago, a 10W-40 oil was the norm with a 6000 - 10000 mile service interval. But, typically after 4- 5,000 miles, the long-chain additives required in a 10W-40 mineral oil will have sheered down to a 10W-30 or less. This may not happen so readily with the better brands, but it still happens.

My reason for using Mobil-1 0W-40 is that even after 10,000 or 20,000 miles, the synthetic oil will still be a 0W-40 grade (because it does not require any long-chain polymer additives), maintaining its viscosity at operating temperature, and will still give better protection during cold starts. I have never had any leaks or tappet noises as a result of using it. I aslo tried the TWS 10W-60 and the only difference I noticed here was lower MPG.

The other thing is that when using synthetics you tend not to find any of that brown varnish build up that occurs with mineral oils. This varnish and the build-up of similar deposits is sometimes what helps to seal leaking gaskets. Synthetic oil does not produce any and tends to do a good job of cleaning away exiting desposits and this can reveal leak problems. However, there are now synthetics designed for older engines, which contain additives to rejouvinate old gaskets and restore their elasticity.

Yes synthetics costs more, but I am certain that your engine will last longer with them. That's not to say that it won't last a long time with the recommended mineral oil changed at the recommended interval.

guys.. you're confusing oil "thickness" and type.

Oil thickness is in NO WAY related to mineral or synthetic. Both can be just as "thick" or just as "thin".

Also, there are a dozen definitions of "thickness" or viscosity. This topic is vastly complex - as one finds immediately when looking at a spec-sheet of any modern oil (which can be found on the net).

One more thing: Minearal oil is always inferior to synthetic - as a synthetic oil can be manufactured to cover all properties of a minearal oil. Minus the dirt, that is.

Anyway.. as noted previously.. it's a matter of religious-like belief.

Zitat

ny decent engine builder will tell you that the tolerances in the V8 & basic V12 are no where near those of other high performance engines that DO require the very best Synthetic oils, so no need really to go & figure.

Well... back in the day of the 8, there was some oil quality and viscosity request from BMW. All modern oils with the same viscosity index will easily surpass that old quality request. Also.. BMW has released all LONGLIFE oils for the old M70 (as can be found in the BMW TIS). So.. all modern oils are fine.