engine oil question?

[scurran83]

My oil light came on over the weekend. I put a small drop of 10W 40 in until i buy more. But i was just wondering if this is the best for the engine and how much should i put in?

[murran]

10w40 is fine, make sure its a semi synthetic (most are nower days).

as for how much to put in..... i presume yours has a dipstick too??? minimum to maximum is around 3/4-2/3 of a litre....

the oil light? was it the level light or the pressure light?

[shaudy]

another oil question,what is the best oil to put in my engine ive heard mobile1 is too thin any truth in this? just finished rebuild so all new gaskets in.c

cheers

[maxfield]

If you've replaced the rings then use cheap mineral oil for the first 1000 miles!

[scurran83]

It was just the OBC computer light came on to check the oil. Went out straight away when i put a drop in it. Ill stick with the 10W 40 so. Thanks for the advice

[djezd]

Mobil 1 too thin?

Thinness is not really anything to do with oil leaking?

If you look at the data below from mobil's and castrol's website, you'll notice that the viscosity at 40 degree C is 80 centistrokes i.e. thickish. then when the oil heats up and thins to 14 centistrokes at operating temperature. You'll notice that castrol edge is slightly thinner than mobil 1 at operating temp. You'll also perhaps notice that mobil 1's mineral S 10W-40 and 15W-40 also thins down to 14.4 centistrokes at operating temp.

So with that in mind, why would mineral 10W-40 stay in the motor better...if it always stays at 40 degrees then i guess yes a visosity argument...but it does not so we need an alternative theory.

Viscosity is also only loosely associated with lubricity, take a fully synthetic 10W40 vs a 10W40 mineral and the fully syn would be slipperier for longer, the base oil is more thermally stable in synthetic oil. And it is this improved lubricity that improves the mpg by switching to say 0W-40 FS. Nearly all the new VAG group cars use FS 0/5W-30 this improves the mpgs and gets their cars under the g/km of CO2.

The leaking that sometimes occurs is more due to the cleaning of the gaskets of vanishes gung etc. out exposing the holes in the gaskets.

Typical Properties

Mobil 1 0W-40
Value
Viscosity, ASTM D 445
cSt @ 40º C 78.3
cSt @ 100º C 14
Sulfated Ash, wt%, ASTM D 874 1.2
Phosphorous 0.1
Flash Point, ºC, ASTM D 92 230
Density @15º C kg/l, ASTM D 4052 0.85
Total Base Number (TBN) 11.3
MRV at -40ºC 26242
Viscosity Index 186
HTHS Viscosity, mPa”¢s @ 150ºC, ASTM D 4683 3.7

Typical Properties (mineral)

Mobil Super M


SAE Grade 10W-40 15W-40
Viscosity, ASTM D 445
cSt @ 40ºC 98 107
cSt @ 100ºC 14.4 14.4
Viscosity Index, ASTM D 2270 157 141
Sulphated Ash, wt%, ASTM D 874 0.91 0.91
HTHS Viscosity, mPa.s @ 150°C, ASTM D4683 3.95 4.00
Pour Point, ºC, ASTM D 97 -30 -24
Flash Point, ºC, ASTM D 92 230 230
Density @15ºC, kg/l, ASTM D 4052 0.870 0.885
Typical Properties

Mobil 1 Turbo Diesel 0W-40
Value
Viscosity, ASTM D 445
cSt @ 40º C 78.3
cSt @ 100º C 14
Sulfated Ash, wt%, ASTM D 874 1.2
Phosphorous 0.1
Flash Point, ºC, ASTM D 92 230
Density @15º C kg/l, ASTM D 4052 0.85
Total Base Number (TBN) 11.3
MRV at -40ºC 26242
Viscosity Index 186
HTHS Viscosity, mPa”¢s @ 150ºC, ASTM D 4683 3.7

Castrol Edge Sport 0W-40
Flash point Closed cup: 244°C (471.2°F) [Pensky-Martens.]
Colour Amber.
Physical state Liquid.
Odour Oily.
General information
Appearance
Important health, safety and environmental information
Pour point -60 °C
Density 838 kg/m3 (0.838 g/cm3) at 15°C
Solubility insoluble in water.
Partition coefficient >3
(LogKow)
Viscosity Kinematic: 75.7 mm2/s (75.7 cSt) at 40°C
Kinematic: 12.8 mm2/s (12.8 cSt) at 100°C