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Old 27-01-2012   #16
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Re: Oil in my Fiat!

Quote Originally Posted by bgunn View Post
It gets thinner (particularly at operating temperature), when it has been used in an engine for some miles - because of the loads the oil molecules are subjected to, effectively shearing them apart and breaking them up. It is the long chains of polymers in the oil that give it the viscosity..
Excuse the long post (this is die hard territory )

Just to clarify about oil as it ages getting thicker - it does get thinner as you rightly pointed out but then gets thicker. I'm not too sure if that was what you were saying but here is a few references to back it up. I included a 'reference' to your 'polymers' towards the end. In the last article they were dubious about the real benefits of 'economy oil' and on balance preferred to increase the 'base' viscosity.

The source for this might be a bit dubious…
http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1489572 (#1489905 - 06/06/0904:40 PM)
The general pattern for engine oils is to shear a bit thinner, then get thicker when they are really beat up and old.

http://ferrarichat.com/forum/faq.php?faq=haas_articles
The reality is that motor oils do not need to be changed because they thin with use. It is the eventual thickening that limits the time you may keep oil in your engine. The limit is both time itself (with no motor use) and/or mileage use. The storage of motor oil in your garage, particularly mineral based oils, slowly ages the oil limiting its use later. Do not store huge volumes of oil in your garage that is exposed to extremes of temperature.
Motor oil becomes permanently thicker with exposure to northerly winter type weather.

http://neptune.spacebears.com/cars/stories/amsoil.html
Mile 8000 -- Bryan Savage, May 1, 2004.
Oil/Vehicle miles: 8,130 / 39,106
Oil added after sample: none

A road trip caused us to miss our sample by a hair over 100 miles. At this point the oil looks black, like used oil ought to. It also continues to thicken up, and is now officially a 5W40 oil instead of the 5W30 we poured in there.
Mile 13,000 -- Jochen Lellesch, November 5, 2004.
Oil/Vehicle miles: 13,001 / 43,977
Oil added after sample: none

Ah, the second-to-last sample. By rights it should be the absolute last sample, but we're going to spot Amsoil one more after this. At 13,000 miles, Amsoil continues to hold steady -- clearly, Amsoil can last much longer than we initially thought possible. That is provided, of course, that you have no problem with the oil thickening way out of grade (many people don't, which is why we continued the test despite our own reservations about it now being a solid 40-weight oil). Well, one more sample to go, and then we'll enter the next flush period, which should settle whether the oil is contributing to the fuel economy drop.

There’s a good summary at the end…
http://www.machinerylubrication.com/Read/518/motor-oils
Another factor in fuel economy is temporary polymer shear. These polymers are additives known as viscosity index improvers (or modifiers). Polymers are plastics dissolved in oil to provide multiviscosity characteristics. Just as some plastics are tougher, more brittle or more heat-resistant than others, different polymers have different characteristics.
Polymers are huge molecules with many branches. As they are heated, they uncoil and spread out. The branches entangle with those of other polymer molecules and trap and control many tiny oil molecules. Therefore, a relatively small amount of polymer can have a huge effect on oil viscosity.
As oil is forced between a bearing and journal, many polymers have a tendency to align with each other, somewhat like nesting spoons. When this happens, viscosity drops. Then when the oil progresses through the bearing, the polymer molecules entangle again and viscosity returns to normal. This phenomenon is referred to as temporary shear.
..........
The best protection against wear is probably a product that is a little thicker (such as SAE 10W-30 or 15W-40) and has more antiwear additives than the oils that support the warranty. The best oil for your vehicle depends on your driving habits, the age of your engine and the climate you drive in, but it is not necessarily the type of oil specified in the owner’s manual or stamped on the dipstick.

So in a nutshell 5w40 as per manufacture's recommendation and it also explains why Fiat increased the viscosity to 10w50 for the Abarth models.
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Old 27-01-2012   #17
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Re: Oil in my Fiat!

Very nice, wheeling out google for the answers

Seriously, if the oil is thicker due to old age, you are *seriously* tight fisted, or lazy, because it has to be left in there for absolutely ages beyond it's change interval to go like that. The one article about amsoil you mention above where it talks about 100 miles over interval is, in my experience, complete crap. Maybe one in a million, but for most, no.

Bear in mind that the Yanks are obsessed about oil changes, too, so take what they say with a large pinch of sodium chloride, specifically when you're talking about Fiat Powertrain products.
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Last edited by bgunn; 27-01-2012 at 19:49.
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Old 27-01-2012   #18
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Re: Oil in my Fiat!

Quote Originally Posted by bgunn View Post
Very nice, wheeling out google for the answers

Seriously, if the oil is thicker due to old age, you are *seriously* tight fisted, or lazy, because it has to be left in there for absolutely ages beyond it's change interval to go like that. The one article about amsoil you mention above where it talks about 100 miles over interval is, in my experience, complete crap. Maybe one in a million, but for most, no.

Bear in mind that the Yanks are obsessed about oil changes, too, so take what they say with a large pinch of sodium chloride, specifically when you're talking about Fiat Powertrain products.
I only posted a 'snap shot' of what's out there. The amsoil case study was posted before but it was under the Mobil one study. Anyway, you are probably one of the few that would be 'able to get into it' since TBH I was getting out of my depth. The only 'gem' that I got was from the Mobile one study that by topping oil up you can extend the 'life' of the oil plus there seemed to be an optimium time to change the oil.

Anyone it just goes to prove that you can find the 'right' answers if you look hard enough but I would agree with you that oil gets thinner as it deteroriates. I can only think that when it gets to a 'thick' stage it must be full of junk.
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Last edited by loveshandbags; 27-01-2012 at 20:54. Reason: grammar changes
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Old 27-01-2012   #19
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Re: Oil in my Fiat!

Exactly - it's full of sludge, and I'd hate to look at the filter of an engine that contains such stuff. Usually they're completely blocked and just lift the bypass valve every time the engine starts, otherwise they collapse, both ways = no filtration.

Definitely change your oil at that point
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Old 28-01-2012   #20
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Re: Oil in my Fiat!

Quote Originally Posted by loveshandbags View Post
I still would use the 5w40 viscosity in Greece if I regularly red line and don't do regular oil changes. IIRC Jason does oil changes every 5K ?
As I stare at the box of a dozen oil filters on the shelf and contemplate my obsessive nature, yes, I am compelled to admit that I change oil often
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Old 28-01-2012   #21
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Re: Oil in my Fiat!

Quote Originally Posted by jnoiles View Post
As I stare at the box of a dozen oil filters on the shelf and contemplate my obsessive nature, yes, I am compelled to admit that I change oil often
I personally think you are pefectly normal! When I had my Neon on the road, I used to go to the Chrysler dealer and buy five oil filters at a time. Changed the oil in that every 6000 miles without fail. Certainly never did the old girl any harm. Rather bizarrely, the genuine oil filters were always cheaper than going into a motor factors and buying an aftermarket one and personally, I always think it's safer buying genuine anyway.
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Old 28-01-2012   #22
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Re: Oil in my Fiat!

Quote Originally Posted by frupi View Post
I personally think you are pefectly normal! When I had my Neon on the road, I used to go to the Chrysler dealer and buy five oil filters at a time. Changed the oil in that every 6000 miles without fail. Certainly never did the old girl any harm. Rather bizarrely, the genuine oil filters were always cheaper than going into a motor factors and buying an aftermarket one and personally, I always think it's safer buying genuine anyway.
Mobile one had an extended synthetic oil that they guarantee for 15000miles but only if you use their special filter that is of course if the oil suited your engine. So there would appear to be a difference in the quality of filters.
http://www.mobiloil.com/usa-english/motoroil/other_products/mobil_1_extended_performance_oil_filters.aspx
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Old 28-01-2012   #23
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Re: Oil in my Fiat!

Quote Originally Posted by loveshandbags View Post
Mobile one had an extended synthetic oil that they guarantee for 15000miles but only if you use their special filter that is of course if the oil suited your engine. So there would appear to be a difference in the quality of filters.
http://www.mobiloil.com/usa-english/motoroil/other_products/mobil_1_extended_performance_oil_filters.aspx
I wasn't aware of this particular oil nor the special filter, I do know though that Mobil oil had been put in my Caddy on my last couple of services costing about £50 for five litres of the stuff. I since found out that General Motors market their own fully synthetic long life oil, Dexos 2, which is approved and is the correct grade for my Caddy engine and it's half the price. I kind of feel a little bit fed up that my dealer would stick in the most expensive oil they have rather than putting in the GM oil. I can only surmise that this is how dealerships make up some of the profits on servicing?

I still haven't asked the Fiat main dealer what oil they intend putting in our 500 at service time. That's a question for next week!
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