Stupid oil question

madmanbob · Post by **madmanbob** » 27 Feb 2006, 22:34

Whether you live in the desert or the UK once your engine gets up to operating temperature then it will be around the same in either place. The thermostat will open at around 97C and the oil will stay at a similar temperature as long as the car is moving.
What could be concerning is the "cold" figure. A 20 grade oil will take much longer to get to the remote parts of the engine at 10C than a 10 grade oil will. The remote part of the engine would be the camshaft and the hydraulic tappets. The difference in time to lubricate these parts could be as much as 500 revolutions of the camshaft, without oil, that is providing you do not start the engine while pressing the throttle - other wise it could take much longer for the oil to reach.
The "hot" part of the rating is not so much of a problem, the oil will be circulating and a 50 will just give a little more drag than a 40 would.
I know loads of people used 20/50 for years in the UK, I did too as it was the main viscosity for oil. When you have cars around like the old Mini that had its gearbox in the sump, you needed a thick oil. Even Rover specified a 15/40 for the A series engine in later years. I am sure that my dad used to use 20/50 for yaers and it never did him any harm, but we all used motorcycles without helmets then and we know better now.

Mandrake · Post by **Mandrake** » 27 Feb 2006, 22:47

Hi,

Thanks for the comments, although a couple of things I will comment on - where did you get 97 degrees for the thermostat opening ? It is more like 83 degrees. Mine seems to run at around 78 to 85 in normal driving.

Also the oil temperature isn't automatically at the same temperature as the water - my Xantia has an oil temperature guage and it hovers around 45 to 50 degrees maximum...if the oil really was at 97 degrees it wouldn't last for long....

Regards,
Simon

Post by **Peter.N.** » 27 Feb 2006, 22:51

I know we are getting a bit off the subject here, but I wonder if anyone can tell me why, for the first 1000 miles or so after I change the oil on my 2.1 td XM the hydraulic tapets intermittently clatter, which can be cleared instantly by reving the engine, but become less noisey as the oil ages, by about 4,000 being completely quiet?

Kowalski · Post by **Kowalski** » 27 Feb 2006, 22:56

http://www.carbibles.com/viscosity.html

Have a look

Mandrake · Post by **Mandrake** » 27 Feb 2006, 22:58

Peter.N. wrote:I know we are getting a bit off the subject here, but I wonder if anyone can tell me why, for the first 1000 miles or so after I change the oil on my 2.1 td XM the hydraulic tapets intermittently clatter, which can be cleared instantly by reving the engine, but become less noisey as the oil ages, by about 4,000 being completely quiet?

Oil initially too thick to pass through the tiny oilways that feed the hydraulic tappits during the low oil pressure of low revs ? (Just a guess here)

Oil gets thinner as it breaks down with age and may work better as a hydraulic oil for the tappits as it ages even though its lubricating properties for the rest of the engine deteriorate...

What grade of oil are you using ?

Regards,
Simon

Clogzz · Post by **Clogzz** » 28 Feb 2006, 10:52

Mandrake wrote:Have I made a mistake

No, I've used Castrol GTX 20W-50 in my old bombs when living in Collaroy, near Sydney, where the lowest temperature was 7ºC.
It does say 'for older engines' on the container of GTX.
In the Xantia, I use Castrol GTX 2, also 20W-50, supposedly a bit more of an upmarket oil.
I've also used GTX 3, 15W-40, which is more detergent than GTX 2.
Despite living now over 800 km north of Sydney, the lowest winter temperature is 3ºC, and the usual summer temperature is 30ºC.
Last winter, I thought that the engine had a slight tapping sound when cold, with the GTX 2, 20W-50.
Next oil change will be GTX 3's turn again, 15W-40, to 'hear' what difference it will make in winter.

The finding over the years, with very ordinary engines, is that oil is oil, providing that it's from a responsible manufacturer.
The only bad oil ever used was Woollies 'home brand', thin and clear, and abnormally cheap at half the going rate.

Post by **Peter.N.** » 28 Feb 2006, 11:19

Thanks Simon, that sounds logical. I think I am using 10/40, I cant remember, I get whatever is cheapest at the time. I get mine from Trago mills, only in the west country at the moment, very cheap.

rpaco · Post by **rpaco** » 28 Feb 2006, 14:11

I should stay away from there in the summer if I were you! (Trago Mills) Its hell on earth in the tourist season.

Just been to check the oil I bought for the Xantia (Haven't doen it yet its too cold out there) and its Car Club from Asda, "Diesel 15W-40 API CF4 for Diesel or API SG for petrol engines" it says. It was £5.96 for 5 litres. Now that I'm an old git I dont drive that far any more with average annual mileage of only about 6000 miles. So this should do for most of the summer.

Supplpementary! Does global warming mean that the average requirement for oil grades wil change?

Post by **Peter.N.** » 28 Feb 2006, 14:42

Sounds like the same stuff and about the same price, rapco. Well, I'm retired now but I still seem to be knocking up about 20k miles a year, so I will keep buying the cheap stuff.

Best time to go to Trago's (Newton Abbott) is about 3.00 PM, everyone else is leaving then!

Mandrake · Post by **Mandrake** » 28 Feb 2006, 18:58

Clogzz wrote:
Mandrake wrote:Have I made a mistake
No, I've used Castrol GTX 20W-50 in my old bombs when living in Collaroy, near Sydney, where the lowest temperature was 7ºC.
It does say 'for older engines' on the container of GTX.

Oh crap.... I didn't notice that

I should have read the fine print on the back.

In the Xantia, I use Castrol GTX 2, also 20W-50, supposedly a bit more of an upmarket oil.
I've also used GTX 3, 15W-40, which is more detergent than GTX 2.

Hmm, I don't remember seeing either of those on the shelf when I got the GTX....and this was at a place with a fairly large selection...

I think my conclusion is that I'll leave it in for now (it seems to be running fine, and there are no hydraulic tappits on the 8 valve engine...) but for the next change I'll look at a more suitable type, perhaps 15W-40. Thanks.

Regards,
Simon

stevieb · Post by **stevieb** » 28 Feb 2006, 23:18

AndersDK wrote:Opposite : in cold climates with many real cold starts in deep frost, you want a thinner oil to be sure the oil will stlil flow easy at the starting temp. Like a 10W-30 or 5W-30, even a 0W-20.

AndersDK wrote:And I can NOT imagine you would have any cold start issues because of a thicker oil.

I'm saying nuffin'

I just know thinner oil meant the battery never struggled on mine in sub-zero temperatures. The fact that the Castrol stuff was Magnatec maybe made things worse - assuming the advertising claims are anything like true. Thicker oil AND it's stuck like a magnet to every moving surface - for that first few seconds or more it's probably more like glue than oil...

Clogzz · Post by **Clogzz** » 01 Mar 2006, 12:16

Mandrake wrote:Oh crap

Nothing to worry about, Castrol GTX is an API SG oil, as the owners’ handbook says to use.
If there was no GTX 2 & 3 at a place with a fairly large selection, it’s an indication that there’s no sufficient requirement for them.
I have travelled twice around Australia and through the centre using GTX in my old bombs with hydraulic lifters.
Temperatures ranged from –4ºC to 36ºC, and there never was any hint of trouble.
Mobil service stations sell 5 litres of 15W-40 for $A26.
Maybe that you have that in NZ too.