which oil ?, 5-30 or 10-30 Options

[NaderG]

which one is better for a 5sfe with 99,XXX , no leaks and in temps that goes over 100 F ( cali ) ??

[Bitter]

iirc 10w30 is what it should run as indicated by the manual.

[NaderG]

iirc 10w30 is what it should run as indicated by the manual.

well in the manual it says that i should use 5w30 for high temp climate , indicated by arrows and stuff... i asked my question because i am not sure if this also applies to a high milage engine

[soven]

wouldnt be a really big difference. just use 10-30

[Insanity-74]

Borrowed from "Oilmans" (Guy) post from the GT4OC.

"0w-40, 5w-40, 10w-40 and 15w-40 are all the same thickness (14 centistokes) at 100degC.

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 more viscous the fluid.

As viscosity varies with temperature, the value is meaningless unless accompanied by the temperature at which it is measured. In the case of oils, viscosity is generally reported in centistokes (cst) and usually measured at 40degC and 100degC.

So, all oils that end in 40 (sae 40) are around 14cst thickness at 100degC.

This applies to all oils that end in the same number, all oils that end in 50 (sae 50) are around 18.5cst at 100degC and all oils that end in 60 (sae 60) are around 24cst at 100degC.

With me so far?

Great!

Now, ALL oils are thicker when cold. Confused? It's true and here is a table to illustrate this.

SAE 40 (straight 40)

Temp degC.........................Viscosity (thickness)

0..........................................2579cst
20..........................................473cst
40..........................................135cst
60..........................................52.2cs t
100........................................ 14cst
120.........................................8.8cst

As you will see, there is plenty of viscosity at 0degC, in fact many times more than at 100degC and this is the problem especially in cold weather, can the oil flow quick enough to protect vital engine parts at start up. Not really!

So, given that an sae 40 is 14cst at 100degC which is adequate viscosity to protect the engine, and much thicker when cold, how can a 0w oil be too thin?

Well, it can't is the truth.

The clever part (thanks to synthetics) is that thin base oils can be used so that start up viscosity (on say a 5w-40 at 0degC) is reduced to around 800cst and this obviously gives much better flow than a monograde sae 40 (2579cst as quoted above).

So, how does this happen, well as explained at the beginning, it's all about temperature, yes a thin base oil is still thicker when cold than at 100degC but the clever stuff (due to synthetics again) is that the chemists are able to build these oils out of molecules that do not thin to less than 14cst at 100degC!

What are the parameters for our recommendations?
Well, we always talk about good cold start protection, by this we mean flow so a 5w will flow better than a 10w and so on. This is why we recommend 5w or 10w as the thickest you want to use except in exceptional circumstances. Flow is critical to protect the engine from wear!

We also talk about oil temps, mods and what the car is used for. This is related to the second number xw-(XX) as there may be issues with oil temperatures causing the oil to be too thin and therefore the possibility of metal to metal contact.

This is difficult to explain but, if for example your oil temp does not exceed 120degC at any time then a good "shear stable" sae 40 is perfectly capable of giving protection.

"Shear stability" is important here because if the oil shears it thins and that's not good!

However, if you are seeing temperatures in excess of 120degC due to mods and track use etc then there is a strong argument to using an sae 50 as it will have more viscosity at these excessive temperatures.

There are trade offs here. Thicker oils cause more friction and therefore more heat and they waste power and affect fuel consumption so it's always best to use the thinnest oil (i.e. second number) that you can get away with and still maintain oil pressure.

I hope this helps explain a bit.

Cheers

Guy."

[NaderG]

cool , i am guessing this also applies to the 30's ...anyways , i checked the manual and its the other way arround , its 10w-30 for temps above 100 , and i was wrong , the thing is , i already put 5w-30 in the motor , but well , i guess it wouldnt hurt ... would it ?

[soven]

continue putting 5-30, It would not hurt.

[NaderG]

OK , problem : when i was buying my oil , i ran into one of those motor flush things , i added it to the old oil , ran the car at ilde for 5 mins ( according to directions ) and drained , left to drain for a while, then put the new oil in ..... level is ok , everything seems good .... the problem is that when i start the car after being parked for hours ( engine cold) , it sounds like oil isnt reaching everywhere its supposed to , this kind of loud sound and the oil lamp stays on for about 30 secs , then the light goes off , the sounds goes away and engine runs good ..... what is this ???? i checked my oil level , its ok but it seems to me like the oil still smells like that flush fluid , and a couple of times when i pull the dipstick out , i can see what seems to be like sludge on the absolute edge of the dipstick .... i read a couple of articles online saying that the 5sfe also develops sludge problems if not pampered .... something that the previous owner didnt do ..... so what is it that can i do ???? how can i solve this problem.... i been using mobile 1 supersync extended performance oil ( like 7 bucks a quart ) .... so what can i do ???? i want to drain the current oil and fill it with another , but as you can see , it will be expensive and i am low on cash ..... any suggestions ???? plz !!!

[LewFX]

for that price i could have got you some royal purple! i pay 65 a case

[cHinaman727]

So for the people from Houston TX, where we get hot and humid, what do you use? I got bout 700 miles till I need an oil change.

Just gimme a name and I'll go grab it and do it.