Coisman - Our father give us loads of wonderful and amazing advice in life but unfortunately that is one bit of advice that is not recommended.
Due to the wonderful nature of gravity the oil inside the engine ends up at the bottom in the sump overnight with very little oil at the top of the engine.
SLX is a 5W30 which means that its viscosity at startup is 5 and at operating temperature the viscosity is 30. This is measured at 0 degrees celsius in a laboratory. Here is some interesting info to ponder over.
At startup there is a moment of no/little protection within the engine for a few seconds, this all depends on the startup viscosity of the oil:
5W - Takes approximately 6 seconds to penetrate the entire engine at startup.
10W - Approximately 13 seconds
20W - Approximately 24 seconds
This is due to low oil pressure and poor circulation. This is why on cold morning you can hear your lifters for a few seconds and then its gone... Thats the oil reaching the top of the engine for the first time.
Lets say for example you start your car cold twice a day... Thats 12 seconds per day. 84 seconds a week and 336 seconds a month which is approximately 5 minutes a month. Which is an hour a year. Lets say your car is 5 years old. This means that for 5 hours of your cars life it has been run cold (Which is when engine tolerances are at their worst), with very little to none protection.
Nevermind your auto choke which is pumping twice as much fuel into the engine, running down your cylinders and nevermind the condensation this causes in your exhaust which will lead to rust...
The most wear experienced by an engine is at startup, this is proven fact.
Driving your car from JHB to my doorstep in Cape Town causes less wear than a couple of cold starts.
For this exact reason it not recommended to allow the car to idle at startup but rather to start and drive off straight away. This allows full circulation and oil pressure to get the oil moving faster and allows the temperature of the oil to increase quicker allowing the polymer to expand to 30 where it can provide its ultimate protection.
You must remember that one of the only reasons we have multi-grade oils is to cure the wear caused at startup. Whilst your car is idling outside your oil although circulating is only at say 25 viscosity so its circulating but it isnt protecting half of what it should if it were at 30 or 40 depending on the grade you use.
Idling the car for a few minutes after driving is noble and nobody can fault that but it isnt completely necessary on NA engines. This is vital though on engines with turbo's though - But thats another lesson.
So Coisman, rather start and drive straight away and get her juices flowing. She will get to operating temp quicker, the oil will do its job quicker and your fuel consumption will improve quite a bit too.
The E90 I gather has SLX (assuming from its last service) but was topped up last year with 1l of Syntium. The other cars all have SLX...
Assuming the car has SLX which we can confirm by calling the dealer that last serviced the car then a flush (although still recommended) is not required. A drain and replace with the Liqui Moly will be alright as both SLX and Top Tec are hydro-cracked so both share a common mineral oil base. Whatever SLX remains in the engine wont be much of a bother for the Liqui Moly and you wont have any issues. They are mixable but its better to rather try keep your fresh oil "pure" for want of a better term.
Hope this helps. You may notice I moved to my pc for this... :rollsmile:
All these men discussing lube so late at night... Tsk Tsk
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