A&Q about 350Z
Q:
i was on this site and asked for an oil recommendation, here is the reply.
Mathew,
Thanks for the mail.
For the Golf the 10w-40 semi is fine, you could if you wanted to move up to a
5w-40 full synthetic, there will be no issues i doing this and you will get
longer drain intervals, less wear etc.
Have a look at Motul, Fuchs and Silkolene.
Regards
Guy.
Opie Oils
anyone gone for a 5-40 fully synth before? i take it it will be thinner? mine leaks enough as it is.... may try it tho :P
A:
5W/40 oil is thicker when its cold, than 15W/40 when its warm. So its okay to use.
Basically, the W is a winter rating, at a cold temperature, oil is always thicker at colder temperatures. Its not a physical measurement, just an index.
A:
Utter shוte, the 5w40 is thinner when it's cold. The higher the number, the thicker the oil. so a 5w will be thinner than a 15w on a cold start-up. Once the oil is hot, they will be equally thick.
A:
That should be 5/40 is THINNER when its cold(5) so OK to use as its then the same viscosity rating once its warmed up (40)
A:
Yes as TSC says, utter sh**e! :-)
A:
Feel free to try it - it's unlikely to cause leaks unless you have gunk stopping your oil seals from leaking. Which a high detergent synthetic may remove. In which case you should really replace them anyway!
A:
Yes as TSC says, utter sh**e! :-)
I just have a better and more efficient BS detector than you do.
A:
5W/40 oil is thicker when its cold, than 15W/40 when its warm. So its okay to use.
Basically, the W is a winter rating, at a cold temperature, oil is always thicker at colder temperatures. Its not a physical measurement, just an index.
5W/40 is thicker when cold than 15W/40 when its warm.
A:
No it isn't............ it is SAE 5 when cold. a 15/40 is SAE 40 when it's warm. I did study a bit of tribology, you know......
A:
A bit of reading for you...
A:
No it isn't............ it is SAE 5 when cold. a 15/40 is SAE 40 when it's warm. I did study a bit of tribology, you know......
SAE isn't a unit of viscosity though, is it? Its an index which is based at 2 temperatures, 40°C and 100°C.
I am sticking 100% with my original answer!
A:
Yes, it's based on two temperatures, but you are still wrong......... read up on it a bit, and then decide whether or not you are going to stick with your original answer......
Regardless of whether the SAE rating is a "unit of measurement", it is DERIVED from a unit (nowadays 3 units) of measurement to make it easier for consumers to understand.
A:
A:
Paul C
Even without studying fluis dynamics and physics why do you think the 10/, 5/, 0/ oils be generally more expensive than 15 or 20?
More money is charged for the wider grade band oils because they are more sophisticated and more desirable.
It is desirable to have the thinest oil possible when cold so that it will flow well
Duckhams Q was the first really 'trick' oil - a multigrade. At cold temperatures it was as runny as a 'thin' 20 grade oil but as it heats up the molecules form longer chains making it more treacle like and taking on the properties of a 'thicker' 50 oil
A:
And if you don't believe it, try cooling some 5w40 in your fridge overnight, and heating some 15/40 to 100 degrees in a pan. Then see which is thinner........
A:
Reading the chart:
5W/40 oil is 20cSt at 40°C and 15cSt at 100°C.
15W/40 oil is around 35cSt at 40°C and 15cSt at 100°C.
So, the 5W/40 oil is 20cSt when cold compared to the 15W/40 at 15cSt when warm, ie its thicker when cold than warm.
A:
The arguments against using 5W/40 are not to do with viscosity, its to do with it having a lesser percentage of base oil, because more of it is viscosity modifier. Also, it may have a higher quality rating, so it will have better/more detergent etc in it and could 'wash' off previous deposits from years of using a different quality oil, which might cause issues.
A:
When was the last time 40 degrees was "cold"? Do you live in Egypt?
A:
The arguments against using 5W/40 are not to do with viscosity, its to do with it having a lesser percentage of base oil, because more of it is viscosity modifier. Also, it may have a higher quality rating, so it will have better/more detergent etc in it and could 'wash' off previous deposits from years of using a different quality oil, which might cause issues.
Viscosity modifiers are a tiny percentage of the volume of oil. A higher quality base oil is never a bad thing in my book - and as I aid, if an oil with a better detergent in it removes deposits and causes a leak - then you need to change the seal, because it is leaky and your engine is clogged up with gunk from using cheap oil!
A:
When was the last time 40 degrees was "cold"? Do you live in Egypt?
Its not 'cold' for us, but for an engine it represents the first few minutes of running. I guess that's why SAE chose it for their 'cold' viscosity measurement.
Viscosity modifier alters the temperature-viscosity relationship, but they cannot make oil thinner when its colder, than it is when its hotter - at least not in the quantities they are used in engine oil.
A:
It's not the first few minutes of running that matters - it's the first few seconds, when the engine is starved of oil.
And you are indeed partly correct in your statement about viscosity modifiers - they are used to "thicken" an oil as it gets hotter, which means that you can run a base oil that is thinner when it is cold!
A:
Paul C
Even without studying fluis dynamics and physics why do you think the 10/, 5/, 0/ oils be generally more expensive than 15 or 20?
More money is charged for the wider grade band oils because they are more sophisticated and more desirable.
It is desirable to have the thinest oil possible when cold so that it will flow well
Duckhams Q was the first really 'trick' oil - a multigrade. At cold temperatures it was as runny as a 'thin' 20 grade oil but as it heats up the molecules form longer chains making it more treacle like and taking on the properties of a 'thicker' 50 oil
They are more expensive because they have more additives.
Thinnest isn't necessarily best - if the oil is too thin then it will allow metal-metal contact and not do its job. Hence a manufacturer will specify a small range of oil which you can use, or one grade. Obviously once you are within the recommended range, then there is no advantage in running thicker oil - it just decreases efficiency.
A:
Thinnest is often best, when it comes to a cold oil - hence the 0w30 and even 0w25 oils on the market......... you need to get the oil (even thin oil) circulating round the bearings ASAP after the first crank, otherwise you WILL be getting metal to metal contact!
A:
It's not the first few minutes of running that matters - it's the first few seconds, when the engine is starved of oil.
And you are indeed partly correct in your statement about viscosity modifiers - they are used to "thicken" an oil as it gets hotter, which means that you can run a base oil that is thinner when it is cold!
An engine would be "starved of oil" only because its flowed down (gradually over time, due to its viscosity) the upper surfaces back to the sump, after last time it was run hot. And, since 5W/40 and 15W/40 are the same viscosity when hot, they'd have flowed down the same. So there is no advantage here.
Perhaps there is a small effect if you ran a car for a few minutes, then switched it off for an hour, then ran it for another few minutes, etc. But the main damage here is 'cold start corrosion' which relates to exhaust gases, not really the oil problem. So its good advice if you switch on your car just to move it, to actually leave it running for 10 minutes and let it warm up. This heats up the exhaust and thus prevents water building up in here, which corrodes it. But I digress...
A:
Thinnest is often best, when it comes to a cold oil
Agree! So long as its not thinner than the equivalent hot oil viscosity for the manufacturer's recommendation.