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Discussion Starter · #1 ·
i changed my oil on the friday befor nads with seliena oil and when i drove down to kettering the car was over heating to 110-120 not good had to have heating up full to keep temp down. i drained the rad no probs there the stat was ok to 2 main pipes were hot now it is allway over heating.

i think that the oil is to thin so it heats really quick and that heats the water

should we use thicker oil in summer(less temp)
should we use thiner oil in winter(heats quicker on cold days)

any thoughts people as i went to glasgow today and it really was hot outside and in the car. :eek: :eek: :eek:
 

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You shouldn't get a noticeable difference in how quickly the oil heats up. One oil may conduct heat better than another but the difference shouldn't be THAT dramatic.

Check that you put enough in there... it may have settled down and need a top-up. Less oil will have more work to do.

I think it's environmental - it's blinkin' hot at the moment - my own oil goes to 100 down the local A-road, which it doesn't normally. The oil is normally cooled by the water and iif the water temp is 85C it will cool the oil more than if it's 95C.

A thicker oil will get just as hot but the advantage is that it hangs on longer at high temperature.

Ralf S.
 

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Have you changed from Mineral to synthetic too?

There can be a dramatic change in oil temp from one to the other, with synthetic running higher, but this should not affect the water temp, that is more likely to be a problem being made apparent by the weather.

My comment on the oil was an observation from when I first started racing Caterhams, in the Academy (you have to buy a new car). Caterhams's advice was to run the engine in for 500-1000 miles on mineral oil then switch to synthetic. When I made the switch, the oil immediately ran over 10 degrees hotter for the same constant speed. Others found the same. The water temp never moved - indeed it never moved even when running long stints on track, where the oil would be 110-120 degrees (which is fine as long as it is synthetic and you change it regularly!).
 
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It must be coolant related, we have extreme hot weather conditions in South Africa & I only use Castrol Magnatec oil in my 145 since new & the temp always runs at 95 degrees ( normal ) winter or summer. Check that the coolant/water ratio are spot on or you might get overheating problems :D
 

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I guess it's water temp, unless it's a 146 with an aftermarket oil temp gauge. I wouldn't expect thin oil to cause higher water temperature than thick oil; if anything, the reverse. Thicker oil is harder to shear, so you get more heating from bearings, crank churning etc. Also, thicker oil has poorer heat transfer, so for a given oil temperature, you'd expect a hotter water temperature.

I expect that jwyatt's experience of higher oil temperatures using synthetic is due to the same affect; synthetic oil is better at cooling the engine than mineral oil, so the oil gets hotter whilst the engine gets a bit cooler.

No matter what oil you use, or what temperature it gets to, running at 110-120C indicates some other problem; either running low on oil as suggested, low coolant level, maybe a water pump problem, a blocked / corroded radiator, or sitting in traffic with a dodgy rad cooling fan?
 

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Hey Paul, just going off what your rad looks like, I would say get it changed. You'll notice a hell of a difference...honest.
I got mine from advanced radiators at Newburn...it was £80 ish.
P.S. I did an oil change with the same oil just before NAD and didn't notice any diff on the journey, but then my rad is only 8 months old.
Hope this helps confuse you even more...Alfa's eh...complicated beasts, but you gotta love em :lol:
 

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Discussion Starter · #8 ·
ok sent a e-mail to Selenia last night and just got a reply.they thinks that it is the oil and as i told him how old the oil was ,consistancy flow cup time and colour he concluded that the oil may be to old and started to brake down. i got some 10/40 from asda and the thickness off the oil was alot more than selenia so im going to change the oil again. and also there is 2 kinds of selenia 20k for the car and if you dont use the right 1 you can have probs.
 

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Incidentally, don't ALFA recommend both selenia oils; one for normal use, and the other for "sporty" driving?
 

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I suspect the main difference is that the lower spec oil will degrade more quickly, leading to more deposits in the oil galleries etc. The only problems I have heard of from up-speccing oil from mineral to semi to fully synthetic is that the 1) the detergent packages of synthetic oils can dislodge carbon deposits left from mineral oils which then migrate and block oil passages, and 2) some synthetic oils can have different seal swelling characteristics. Old seals which have lost their elasticity can then crack, causing oil leaks. I've never heard of overheating problems caused by changing to synthetic oil :(
 

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paulcanning69 said:
ok sent a e-mail to Selenia last night and just got a reply.they thinks that it is the oil and as i told him how old the oil was ,consistancy flow cup time and colour he concluded that the oil may be to old and started to brake down. i got some 10/40 from asda and the thickness off the oil was alot more than selenia so im going to change the oil again. and also there is 2 kinds of selenia 20k for the car and if you dont use the right 1 you can have probs.
Thats interesting... :confused:
 

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We need more details. I can't see how the oil can cause the water temperature to rise - the heat-soaking characteristics of the oil can't change THAT much can they? It's like saying old tyres run hotter than old ones... they might but not 20% more..

Weird...

Ralf S.
 
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Ralf S. said:
I think it's environmental - it's blinkin' hot at the moment - my own oil goes to 100 down the local A-road, which it doesn't normally. The oil is normally cooled by the water and iif the water temp is 85C it will cool the oil more than if it's 95C.

Ralf S.
Tempted to agree, the day of NAD was damn hot and its been teh same since...except for today when the temp has been lower ;)

Some oils may allow a slightly higher temp but I've never noticed much difference for the kind of driving we do on the roads.

wrinx
 

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mave said:
Incidentally, don't ALFA recommend both selenia oils; one for normal use, and the other for "sporty" driving?
Yes, they recommend 20K 10w40, or Racing 10w60 for spirited driving.


paulcanning69 said:
...there is 2 kinds of selenia 20k for the car and if you dont use the right 1 you can have probs.
They do quite a few other oils as well including 5w30, 15w40 etc, but from their website it seems that there are only 2 types of 20K, the Alfa branded one and the other. They are both 10w40 and seem to meet the same specifications, but the other one also meets an MB spec that isn't listed on the Alfa oil. The Technical Characteristics appear so close that I wouldn't have thought it made any difference which one you used.

And yes, it was very hot on the day of NAD. I drove about 75 miles at a nearly constant 90-100mph (waiting for the speeding tickets to arrive) before stopping at Rothwell McDonalds to grab a quick bite. I jumped straight back into the car and headed for Boughton. I immediately noticed that power was down. Not massively, just lacking that extra urgency above 3-4000rpm. Temperature guage had been a touch above normal, but not much. No lasting effects thankfully, but I can only put it down to the heat.

Buck
 

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What you also need to bear in mind is that thin oils dissapate heat better than thick ones. Ok, sae 60's are thicker at say 100degC (sae 60 = 24cst / sae 50 = 18.5cst / sae 40 = 14cst) so they can withstand heat for longer without losing viscosity and when they do they become sae 50 or sae 40.

But, thick oils generate more friction and therefore more heat.

The question is, at what (sump) temperature is the oil at a viscosity that suits a modern high-RPM engine.

Present day designs seem happy on an oil viscosity of 10 to 15 cSt. (But many are OK on less than 10.) 30cSt is too high at high RPM. It can lead to foaming, air entrainment and cavitation.

......Temp. for 30cSt (Deg. C)...Temp. for 15cSt....Temp. for 10cSt

5W/40...........71...........................90........................117.......
10W/40.........70...........................99........................118.......
10W/50.........80...........................109.......................130......
10W/60.........89...........................119.......................142......

This shows that a 5W/40 or a 10W/40 is perfectly adequate for all engines except those that run an unusually high temperatures.

A good sae 40 can withstand temps to around 120degC and a good sae 50 to around 130degC.

Cheers
Simon
 
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