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rejo
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Going to change all the oils this week on my 300tdi disco, not had it long and have always used 15w40 on previous engines as its resonably cheap and readily avaliable. Had considered 10w40 semi synthetic but have heard reports about oil leaks after changinging to synthetic oils as this engine is surprisingly oil tight I dont really want to encourage oil leaks. I dont know any history on this car so I've no idea what oil has been used before.

So 10w40 or 15w40 or any other suggestions.

Thanks.

Jo

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I think the recommended grade is 5/30 to 25/50 (5.8 litres). If your engine is regularly serviced and in good working order, you should use the right grade for it. Worn engines can be better on a thicker oil, but not too far off of what's recommended when it was new.

15/40 would be a good average I think.

Les.

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In Scandinavia it's sometimes so cold that we empty the engines and run them without oil. When it's time to drain is seen when the polarbears stay inside in front of the fire and don't go out in the streets as they normally do. :blink::D

No, 10W-something is mostly fine and in extreme temps, synthetic oils are available from 0W. Blockwarmers are also common to use to get the fluids a little more user friendly.

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The first number gives an indication of its viscosity at cold(40C) start.

The lower the number the runnier the oil.

The second number is an indication of the oils viscsity at approx 100C (I think).

The higher the number the thicker it is.

There is very little difference between 10W(inter) and 15W, infact according

to an oil specialist I have talked to there is very little difference between

5W and 15W in the Mobil1 fully synthetic oil, which is why 15W doesn't get sold

in Scandinavia. They only sell the 5W-50 fully synthetic here.

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The first number gives an indication of its viscosity at cold(40C) start.

The lower the number the runnier the oil.

The second number is an indication of the oils viscsity at approx 100C (I think).

The higher the number the thicker it is.

There is very little difference between 10W(inter) and 15W, infact according

to an oil specialist I have talked to there is very little difference between

5W and 15W in the Mobil1 fully synthetic oil, which is why 15W doesn't get sold

in Scandinavia. They only sell the 5W-50 fully synthetic here.

Thats' useful information, thanks.

Paul

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The first number gives an indication of its viscosity at cold(40C) start.

The lower the number the runnier the oil.

The second number is an indication of the oils viscsity at approx 100C (I think).

The higher the number the thicker it is.

There is very little difference between 10W(inter) and 15W, infact according

to an oil specialist I have talked to there is very little difference between

5W and 15W in the Mobil1 fully synthetic oil, which is why 15W doesn't get sold

in Scandinavia. They only sell the 5W-50 fully synthetic here.

errr, not quite. :o

This is a reply on a similar topic from another forum.

5w-40 is NOT thinner than an equivalent 15W-40 at operating temp, in fact there may be f%ck all difference at 0*C, and some 5W-40's are thicker than some 15W-40's at 0*C.

An SAE viscosity # is a range, actual viscosity is measured in centistokes (cSt) eg an xW-40 must fall between 12.5 cSt and 16.3 cSt @ 100*C (most apear to fall @ 14-15cSt)

A 0W-xx or 5W-xx is able to pump/flow at much lower temps than a 15W-xx. Pumping viscosity at low temps is measured in centiPascals (cP) and a 0W-xx cannot exceed 3250 cP @ -30*C , a 5W-xx must not exceed 3500 cP at -25*C, and a 15W-xx cannot exceed 3500 cP @ -15*C.

Here's some specs for a few different oils at various temps

Mobil Delvac 1 5W-40. 14.8 cSt @ 100*C. pour point -45*C

Castrol RX Super 15W-40. 14.5 cSt @ 100*C pour point -27*C

Redline 15W-40. 15.1 cSt @ 100*C. pour point -45*C

Penrite HPR5 5W-40. 15.1 cSt @ 100*C. (no pour point given)

Shell Rimula Ultra 10W-40. 14.6 cSt @ 100*C. pour point -30*C

Castrol Magnatec 10W-40. 14.6 cSt @ 100*C. pour point <-35*C

yet at 0*C we get

D 1= 1066 cSt

RX = 1358 cSt

RL = 1122 cSt

HPR= 1350 cSt

RU = 0809 cSt

Mag = 1182 cSt

a 10W-40 (Shell Rimula Ultra) is actually thinner than both 5W's, and a 15W (Redline) is thinner than the 10W Magnatec and the Penrite HPRD5 at 0* !

It's only when you get down to North American type winter temps that the 5W-40's really show an advantage in pumpability.

HPR5 has a cranking pressure (cp) @ -30*C of 5719, yet

Magnetec has a cp of 7000 @ a warmer -25*C.

The only other directly comparable number was for the older CH-4 version of Delvac 1 which had a cp of 3250 @ -25*, and 20,000 @ -35*.

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errr, not quite. :o

This is a reply on a similar topic from another forum.

And how does the info differ from what I said???

Not nitpicking, but if you go into individual oils and look

at the exact specs and get the datasheets Yes, then the other reply is more correct.

But as a general rule of thumb, I don't see how the more complex

answer would help someone choosing an oil in Halfords, without relevant

datasheets and a more indepth knowledge.

;)

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I'd imagine not paul. I would suggest 5/30 for those conditions, or not much higher. -20degC, now that's cold!! :unsure:

Les.

Thanks Les,

It is not that cold all through the winter but can drop to that level. Is it worth going to a 5/30 for all year round use?

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If there's a possibilty of it dropping to that temperature, then I would be inclined to use 5/30. If your summer tempertures climb into the 70's, then it might be wise to use a thicker grade oil for the warmer months. An engine that has an oil that's too thin, or is a bit worn, may rattle quite a bit. As long as you stay withing the manufacturers guidelines, then thin for extreme cold, and thicker for warmer temperatures.

Les.

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And how does the info differ from what I said???

Not nitpicking, but if you go into individual oils and look

at the exact specs and get the datasheets Yes, then the other reply is more correct.

But as a general rule of thumb, I don't see how the more complex

answer would help someone choosing an oil in Halfords, without relevant

datasheets and a more indepth knowledge.

;)

'cause you said the lower number referred to a viscosity at 40*C which couldn't be further from the truth. The lower number refers to an oils pumpability at sub zero temps, my little speil above was merely trying to show that at above zero there was no real difference between most 5w's and 15w's, the differences don't become apparent 'till you get below 0*.

And FWIW, if you were going to experience -20*C starts, I'd be using at least a 10w-40, (and take it very, very easy until warm) or better still a 5W-40 unless you used a block heater

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If there's a possibilty of it dropping to that temperature, then I would be inclined to use 5/30. If your summer tempertures climb into the 70's, then it might be wise to use a thicker grade oil for the warmer months. An engine that has an oil that's too thin, or is a bit worn, may rattle quite a bit. As long as you stay withing the manufacturers guidelines, then thin for extreme cold, and thicker for warmer temperatures.

Les.

Thanks Les

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