The short answer is, "Because they say so"

But lets have a clean and nice discussion on why we should use Synthetic motor oil vs regular mineral oil/dino oil. Hopefully it will help others.

It's time to school me on it. I've found plenty of threads on the different versions and weights of Synthetic (no mention of the weight spec in the Mini owners guide and just a suggestion in the Bentley manual BTW), but no discussion on why. If I've missed a link describing this, please post it below.

I've just had the engine on my R53 fully rebuilt, and the rebuilder (and warrant'er for the next 12 months) put in break-in oil for the first 1K (that's fine and passed last weekend) and told me to use regular mineral oil for the next 5K (I put 5w30 in), then switch to Synthetic "if I wanted too".

I got into this rebuild situation partly because of the ridiculous time span between oil changes (and not checking the remaining volume that it consumed). So there's NO WAY I'm interested in changing the oil every 8000 + Kms (or whatever the OBC says). I understand that there's a rating on the oil that should match BMW's long life rating, but that's assuming you're okay with leaving it that long, and to maintain their warranty.

Some have mentioned they use Synthetic and change it every 5000, but that sounds expensive (given the premium price of the Synthetic oil). I'm not being cheap here - if there's something about Synthetic, then this is what I'll do.

So let's assume you change your oil at 5000 Kms, and your car is out of warranty. What is the benefit of using Synthetic motor oil?

 

I dont know. how ever i have always used regular old oil in other cars and changed it every 3k miles along with the filter, also used motor flush. and when ever i check my internals they were always clean as a whistle and no abnormal wear or increased wear. but a long while back i did find an artical on vwvortex that explained synthetic and regular oil ill try and see if i can find it.

 

First, let's be clear. You got into this situation because YOU failed to check your oil, not due to the long periods. I have been running 15K for years now and my engine is fine but I check it at every other fill up and make sure I am topped off. Also, the oil should meet or exceed the BMW rating. However, remember that the BMW ratings are expensive and some companies don't want to pony up the money for them.

As for the type of oil, you could run dino but I wouldn't go 5K on it, 3k max which means you will most likely spend more money on changes over time. Heat is also a factor if you have an MCS as dino oil can sludge up easier. Those two items alone are enough reason to run synthetic in my book.

 

http://lmgtfy.com/?q=why+use+synthet...of+regular+oil

 

No engine wear.

 

In a nutshell this is absolutely correct, the biggest reason is lifespan & breakdown of the oil, even when a synthetic breaks down it doesn't sludge like a natural oil does, so even taking lubrication out of the equation (which is actually the #1 reason to use a synth.) even properly changed natural oil will leave more residue behind on every single part of your engine every time you change your oil, and over time that small amount of leftover residue will bulid up & start to sludge, and sludge is the biggest contributing factor to poor lubrication on an older motor.

If you were to open up 2 high milage motors that have had their min. req. oil changes (3-5k natural & 12-15k synth) the synth motor will be CONSIDERABLY cleaner.

 

That is exactly the kind of reasons I was looking for. Engine wear and build-up.
Thanks guys.

 

You still have engine wear and will with any oil. Polymers still wear an engine down but it is far less with synthetic.

 

Oil protection for any moving part is never 100%, unless you have magnetic bearings you will have wear. Given that, synthetics reduce wear by a vast amount, and more importantly, dont "fall apart", clump or sludge anywhere nearly as easily as "dino" oils, AKA conventionals. Synthetics were originally developed, as were a huge amount of modern tech, for the aviation and space industries, because of the super-harsh environments and absurd temperatures they encounter. Simply synthetic doesnt degrade under abusive temps and shear conditions the way standard oils do. They also have less "weight" or viscosity changes under temp extremes (hot or cold) and so flow better at
-10F and dont thin out or break down at 400F. I use Mobil 1 exclusively in my Cooper S and my 4 cam GP with what was at the time (1992) a pretty exotic 9.5 comp ratio DOHC V6. I can pop the oil cap on the GP at 186K and see clean but heat burnished metal, as a 20 yr old engine should look. No crud and the engine has never been opened. All interior parts are as-built and it pulled 221 WHP w/o turbos or nitrous. Now are there others just as good, sure. I just like Mobil. I use Red Line in the GPs tranny and they also make motor oil, as does Royal Purple and Castrol.

 

Here is a real-world experience that is fact based. Different car, Dodge with Mitsubishi 2.7 engine. I got it with 70k miles. It was owned by a friend who had died. He did regular oil changes at Jiffy Lube and the paperwork indicated that they used regular bottom-shelf Penzoil. The engine was sludged up to the point that it would lose oil pressure when hot and at idle. Sludge was visible when looking down the oil fill hole. These motors seem to have a reputation for doing that. I did two oil changes in fairly rapid succession with synthetic blend and added a double dose of SeaFoam to the crankcase. Drove conservatively on the witches brew since I felt the lubrication was compromised by the heavy dose of SeaFoam and the gunk being released. Then switched to full synthetic with regular oil changes - no more problems with oil pressure. I gave the car to my yard man and he continues the routine and the thing is still on the road with about 150k.

It is my opinion, based on my experiences that synthetic is the way to go. I think this would be particularly true in a turbocharged car with the coke issues they have with the extra heat duty cycle of the oil.