Oil & Cold Starts - Good Advice from Opie Oils

[oilman]

dAt this time of year, it’s beneficial to use an oil that has good cold start flow properties as it will get to the parts of the engine that need it far more quickly when you turn the key on those sub zero mornings.

The "w" number which means winter is the key here and the lower it is the better cold start performance the oil will have.

A 15w or 20w rated oil will struggle to get around the engine in very cold temps and we would strongly recommend using a 10w, 5w or 0w for better cold start performance.

It is a fact that around 90% of all engine wear occurs on cold start because the oil is at its thickest. The colder it gets the thicker the oil becomes and this affects the rate of flow which affects the rate of wear.

These numbers help to explain the oils thickness and therefore cold flow performance at various temperatures.

Grade.................At 0C.................At 10C..............At 100C

0W/20.............328.6cSt...............180.8cSt.... ........9cSt

5W/40.............811.4cSt...............421.4cSt.... ........14cSt

10W/50............1039cSt...............538.9cSt...... ......18cSt

15W/50.............1376cSt..............674.7cSt...... ......18cSt

20W/50.............2305cSt...............1015cSt...... ......18cSt

Centistokes (cst) is the measure of a fluid's resistance to flow (viscosity). It is calculated in terms of the time required for a standard quantity of fluid at a certain temperature to flow through a standard orifice. The higher the value, the thicker the oil.

Winters in the UK are fortunately not too cold but, below zero temperatures are regular features in some parts of the country.

Compare the thickness of the oil at 0degC and 100degC and you will see the big difference.

Just something to consider on those frosty mornings.

The Opieoils Team.

[havoc]

Very useful, thanks.


Out of interest, what are the issues with the converse - i.e. using a very low viscosity oil in a hot engine...particularly a hot and old/worn engine - will it provide enough lubrication and protection?


(The reason I ask being a lot of the 'classic' car owners use high-viscosity oils like 20W50 which reduce the likelihood (& severity) of oil leaks - 0W20 would, from one friend "piss out of the seals when hot")

i.e. isn't there going to be a 'best compromise' for each individual engine/climate/usage profile?

[Justin]

Really interesting... it's the first time I've ever had the oil blah explained, and I'm embarrassed to say that I'd never asked myself what the hell all that "w" business means before now....

Good oil is one of the most important decisions a car owner can make. Now that I'm used to the 7 series (which drinks more than NINE litres of the dearest stuff on the market every time), I at least get the benefit of every other oil change appearing relatively cheap :rolleyes:

Would be interested in the answers to havoc's questions.

[oilman]

Very useful, thanks.


Out of interest, what are the issues with the converse - i.e. using a very low viscosity oil in a hot engine...particularly a hot and old/worn engine - will it provide enough lubrication and protection?


(The reason I ask being a lot of the 'classic' car owners use high-viscosity oils like 5W20 which reduce the likelihood (& severity) of oil leaks - 0W20 would, from one friend "piss out of the seals when hot")

i.e. isn't there going to be a 'best compromise' for each individual engine/climate/usage profile?

Your mate is right, older engines often have larger tolerances and will often leak a really thin oil, so classic engines usually us a 20w-50.

If thinner oils are used and the engine gets too hot for them, they won't offer great wear protection. You need to look at what the car is being used for. F1 cars use very thin oils, but they aren't overly concerned about wear as it won't be significant over a race or two. It allows an extra few BHP to be released due to reduced internal resistance.

Cheers

Tim

[oilman]

Really interesting... it's the first time I've ever had the oil blah explained, and I'm embarrassed to say that I'd never asked myself what the hell all that "w" business means before now....

Good oil is one of the most important decisions a car owner can make. Now that I'm used to the 7 series (which drinks more than NINE litres of the dearest stuff on the market every time), I at least get the benefit of every other oil change appearing relatively cheap :rolleyes:

Would be interested in the answers to havoc's questions.

BMW are a great example of good oils improving longevity. There are a whole lot of BMWs that have gone well past 250k and they run fine, basically as BMW spec good oils from the start. Okay they are better built than most from the start, but the oils help.

Cheers

Tim

[Justin]

BMW are a great example of good oils improving longevity. There are a whole lot of BMWs that have gone well past 250k and they run fine, basically as BMW spec good oils from the start. Okay they are better built than most from the start, but the oils help.

Cheers

Tim

Have to agree with all that

BUT... The NSX (80k) is running even sweeter than the 7 :yes:

[nobby]

You have a lot of nerve saying that on this site! :)

If they are so well built why do alot of them spend their time back at the dealers and wired up to Bavaria when they break down?

and why do nearly all 320 DIEsel engines have blown turbo issues at over 70k!

WELL BUILT ... my ar$e! :laugh:


Okay they are better built than most from the start, but the oils help.

[oilman]

Have to agree with all that

BUT... The NSX (80k) is running even sweeter than the 7 :yes:

Yes, but NSXs are a bit special.

[oilman]

You have a lot of nerve saying that on this site! :)

If they are so well built why do alot of them spend their time back at the dealers and wired up to Bavaria when they break down?

and why do nearly all 320 DIEsel engines have blown turbo issues at over 70k!

WELL BUILT ... my ar$e! :laugh:

Okay, perhaps the newer beemers aren't so good, but the mid 90s ones were very well built. Ones where you couldn't connect them to a computer.

Cheers

Tim

[NoelWatson]

Okay, perhaps the newer beemers aren't so good, but the mid 90s ones were very well built. Ones where you couldn't connect them to a computer.

Cheers

Tim

The newer ones are dreadful

[Justin]

The newer ones are dreadful

Interestingly, it's a little bit subtler than that.

Having recently had my 735i (N62) apart, I can say that the engines remains immensely well machined and built.

The problem is neither the machining nor build, which I would contend remain industry leading. Rather, it's the design. Basically, these things are designed by kids in the lab who don't know what goes on in the real world (and I speak from experience, when my bro was on a Formula Student team, it was constantly amazing how little practical experience his colleagues had).

To wit, the N62's stupid design spans the rocker cover over both the block and the upper timing cover, creating a t-junction gasket hell. Oh, and if you think you're gonna take on the dealers and slip the timing cover yourself, the ****-blocking water-cooled alternator means that you ain't going nowhere without BMW specialist tools (unless you're cunning and tenacious).

That's right. water. cooled. alternator. :no:

Modern BMWs are still really well built, they're just really badly designed now, with one beady corporate eye on dealership revenues and the other on customer repurchase rates.

[NoelWatson]

Interestingly, it's a little bit subtler than that.



I'm not sure it is. Our POS 330i ED breaks down every six months on average with the same problem. Misfire. They replace everything and it works for another six months.

[TheSebringOne]

I thought the latest 3 series is the most reliable car in Britain? Had 3.0 petrol in a beamer before 54 reg and had no trouble with it? Someone I know in BMW told me that the 320 petrol is lot more reliable engine wise than the 320 Diesel from around 2000.

[havoc]

Someone I know in BMW told me that the 320 petrol is lot more reliable engine wise than the 320 Diesel from around 2000.
The old 320d engine was a low point for BMW. Lunched it's turbo with embarassing frequency - IIRC due to a key part (impeller or a valve I think?) being made of plastic not metal.

I do wonder if Noel has a Friday-afternoon car or if all modern BMs are going that way - they do get excellent emissions and efficiency results, but is that a result of pushing the engine too far - even simple stuff like EGR isn't great for an engine...