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Old 06-10-2004, 04:46 PM   #1 (permalink)
Harry (Harry)
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Default My local store had a special o

My local store had a special on Shell Helix AF 10W-60 full synthetic. Is this too thick for a 308?
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Old 06-10-2004, 07:56 PM   #2 (permalink)
dave handa (Davehanda)
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Default Probably. The original oil sp

Probably. The original oil spec was a semi-synthetic Agip oil in 10w-50. When Agip discontinued making this, and started only making 10w-40, that became the new standard. For the last several years they have recommended using Shell Helix 5w-40, which is used in the later cars. The local dealer tells me that Ferrari tries to ensure their current lubricants are backwards compatible quite a ways back. At least to the 308 series. From reading the posts by Ali Haas at the "other site" it seems the primary purpose of oil viscosity is to maintain the proper oil pressure at operating temperature. You really want to use the thinnest oil that allows you to maintain optimum oil pressure (around 90 or so psi max in a 308/328). A 5w-40 or 5w-30 may be a better way to go. I am using Mobil 1 5w-30 in my 328 right now, and oil pressure is in the normal range, hitting a max of low 90's psi at 6-7k rpm.

So if you used a 10w-60, at operating temp, you may be hitting max oil pressure limit frequently, and then bleeding off the excess pressure off the valve...depends on what it is set at. On my 328, it was mistakenly set at over 120psi! (I was using Mobil 1 15w-50 at the time) Many 328's are set this way from the factory. I had the updated spring installed which lowered the release to around 93-96 psi. Using a lower viscosity oil can only help matters according to Ali Haas.
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Old 06-11-2004, 04:27 AM   #3 (permalink)
Harry (Harry)
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Default Dave, thank you for your compr

Dave, thank you for your comprehensive answer. I have looked through the extensive oil discussion you mentioned. There seem to be a lot of benefits of the thinner oils (startup wear, oil flow).

Still I do not feel comfortable optimizing the oil spec towards "as thin as possible with acceptable oil pressure" as this is only one of many parameters to look at. Others are sheer stability and viscosity in high temperatures. And one remark to oil temperatures: on the gauge you see an average temperature, the peak temperatures are hit in the bearings and cylinder walls and are some 20-30 degC higher. So I feel better having some safety margin on this.

I will fill in the 10w60, have a look at the oil pressure/temperature and keep you updated. At least this oil is expensive and rated "racing oil"

Regards
Harry
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Old 06-11-2004, 05:15 AM   #4 (permalink)
David Feinberg (Fastradio2)
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Default Harry, I'm 100% in agre

Harry,

I'm 100% in agreement with you as to the argument that "thinner is better..." I too, am not comfortable with this statement, nor is BMW. I recently bought a new M3...and Castrol Motorsports 10w-60 is the specified oil. I called BMW and expressed my concerns re this being a "heavy oil." Their response was that this oil provided extra protection under extreme load conditions, coupled high oil temperatures. Synthetics flow well at low temperatures...so excessive wear under cold start conditions was not a concern.

I find, and continue to find it distubing when people state information that is contrary to what the manuafacturers recommend. Considering what a new engine would cost for my M3, or Boxer...I'm just not going to second guess the engineers who speced the oil reqirements initially.

Regards,
David
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Old 06-11-2004, 07:51 AM   #5 (permalink)
David Jones (Dave)
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Default Something else to consider in

Something else to consider in regards to oil selection, is how the engine clearances are setup on a particular engine.

At any rate, I'm not a big fan of "If it is expensive" it must be good.

Call me frugal, but as often as I change the oil in my cars,
I just buy a high quality Dino oil when it is on sale, and keep it on the shelf.
Why pay more when you can pay less?
And then once a year I run full synthetic oil, (which I also buy when on sale), as a cleaning agent per-say.

Give us a report in a couple thousand miles Harry and let us know how it compares.

Good luck!
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Old 06-11-2004, 11:21 AM   #6 (permalink)
Harry (Harry)
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Default Thanks to all of you for the f

Thanks to all of you for the feedback. Realized that I do not have a 12 mm hex plug at home so I will change oil probably tomorrow.

Regards
Harry
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Old 06-13-2004, 04:26 PM   #7 (permalink)
dave handa (Davehanda)
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Default Understood David, but in this

Understood David, but in this situation, 10w-60 is also NOT the specified weight either. The last service bulletin from Ferrari stated that the specified oil was Agip 10w-40 for the 308/328/Mondial series (http://bingo.cdyn.com/ferrari/328_bulletins.pdf) page 82 (I imagine there is a newer one somewhere stating the Shell Helix 5w-40 is the new standard)...So I guess you are saying stick with 10w-40. Absolutely nothing wrong with that advice.

My BMW specifies 5w-30 synthetic and I would not deviate from that, but in my 328 (17 yo car) there was definite issues with the motor running excessive oil pressures. Most of it can be corrected by putting the correct weight spring in the oil pressure adjustment doo-hicky (techinical description mine)(see page 62 and 104). But if ones engine is still running a bit high, I would error lower viscosity, rather than higher...though the factory spec (10w-40 or 5w-40) should be fine in an engine running correctly and to specification. I guess I got a bit concerned over this specific issue with the 3.2 motors, when we are discussing a 3.0 motor, that generally don't have this issue.

I think Ali said that the oil specifications of 20-25 years ago are so outdated as to be almost useless. I would think that flash point, shear and other specs are so much better than dino oils or semi-synthetic oils from that far back, that it would be difficult to make a poor choice based on those specific variables.

But I am in agreement with you, if everything is fine, then stick with the factory recommendation, it invites the least risk.

Harry, do report back on your findings. I would be curious as to your pressure readings at operating temperature, for idle, 3500rpm and 6000rpm, and how this compares to what you were using previously.

Dave

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Old 06-15-2004, 09:40 PM   #8 (permalink)
Mitch Alsup (Mitch_alsup)
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Default Ali Hass and I developed a ser

Ali Hass and I developed a seris of posts on <the>. I want to inform this group of the current state of our theories, and whil Ali is the 'PHD' on this topic, I sem to be the one who puts the data into a format where everyone else can get a touchy feely indoctrination concerning oil. So what follows is a recantation of my knowledge base concerning oils::

Ali collected a lot of data concerning oils. In this first picture, I have included those oils I feel are within consideration for Ferrari applications:



The verticle axis is logarythmic in CentiStokes while the horizontal axis is linear in temperature.

Stokes are the way kinematic viscosity is measured and basically measures how fast a steel ball bearing falls through a solution. Poise is a measure of the internal resistance of a liquid and basically tells us how fast it flows <e.g.>. The difference between Stokes and Poise is that Stokes is Poise divided by the specific gravity of the liquid.

This next chart shows the bands used to determin if an oil is 30 weight <designated>, 40 weight, 50, 60,... This is a measure of the kinematic viscosity at 100 degrees Centigrade. The kinematic viscosity at 40 degrees centigrade for a 10 weight oil at low temperatures <designated> determins how easy the oil flows at startup. The pair of numbers determs the operating characteristics.


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Old 06-15-2004, 09:53 PM   #9 (permalink)
Mitch Alsup (Mitch_alsup)
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Default Now let us overlay both sets o

Now let us overlay both sets of data

The important thing to notice here is that "for the most part" all the oils fall into the bands corresponding to their numbering system (Whew).

There are three basic kinds of protection oil provides to an engine: a) Journal lubrication, b) sliding lubrication, c) Wiping lubrication.

The main bearings, connecting rod bearings, and cam shaft journal bearings are lubricated by a film of oil that supports a varying load under (basically) constant speed of revolution. In journal bearings there is a hydrodonamic wedge that builds up that supports the monumental sized loads these bearings support, the oil pressure of the engine does NOT support these bearings, but only provides cooling as the oil flows between the journal and the shaft. When an engine is cold and high revs are applied, the oil may be so thick that it solidifies as the hydrodynamic wedge passes over. At this point the oil is stiffer than either the journal bearing (babbit) or the shaft (forged steel). In this condition the oil will scrape the bearing and shaft causing high level of wear.

The piston rings and valves represent sliding lubrication, where the speed of operation varies over eacy cycle. Film strength of the oil provides lubrication and clearance control at the low speed (stopped) end of movement, while hydrodynamic wedge supplied the lubrication during the faster movement stage of the cycle.

Wiping lubrication is where the cam lobe wipes across the cam tappet and pushes the valve in. Very high loads are encountered at high RPMs and a lot of modern oil technology goes into protecting the cam lobe and tappet faces.
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Old 06-15-2004, 10:17 PM   #10 (permalink)
Mitch Alsup (Mitch_alsup)
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Default Ok, so we have had a quick pee

Ok, so we have had a quick peek at viscocity, just how doe any of this have to do with wear. Well, there's the rub, very little data is available to connect viscocity to wear; however, I have heard soories that wear is quadradic, cubic and exponential with respect to various things.

So, with a great leap of faith, I cam up with an explanation that seems to hold water but I advise a judicious grain of sodium chloride.



Here we see the various kinds of wear in functional form. With respect to high performance engines like found in Ferraris almost anyone would be happy with 100,000 trouble free miles, and almost noone bould be happy with 10,000 trouble free miles. We can use this to bracket the wear functions and then use the wear functions to tell us things about oil.

Notice for the range of intrest there is very little difference between exponential wear and cubic wear. So by placing a marker at the inflection point we can see that operation below the inflection point enables long life and operation above the inflection point marker does not.
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