Alfa Romeo Forum banner

1 - 20 of 21 Posts
M

·
Guest
Joined
·
0 Posts
Discussion Starter #1
This is for info only....... :rolleyes:

The oil in my Silverstone runs at about 5.5bar giving it welly when hot.
The V6 only about 3.5bar. Ok so it's above the minimum 2.5bar at full revs, but I just wondered what are the likely causes.

The V6 doesn't use as much oil as the Silverstone and the guages/senders work fine.
 

·
Registered
Joined
·
11,591 Posts
marlon said:
This is for info only....... :rolleyes:

The oil in my Silverstone runs at about 5.5bar giving it welly when hot.
The V6 only about 3.5bar. Ok so it's above the minimum 2.5bar at full revs, but I just wondered what are the likely causes.

The V6 doesn't use as much oil as the Silverstone and the guages/senders work fine.
such things as
1) Oil viscosity at operating temperature which in itself is controlled by whether the oil is synthetic , and its viscosity range etc
2) resistance to flow of oil. Bearing wear leads to less oil pressure for example.


and also depends on the pressure specified by design engineer for a particular engine.
 
W

·
Guest
Joined
·
0 Posts
Discussion Starter #3
...also, may be normal Marlon, my V6 has always showed lower oil pressure than the Twinny ever did...and its never got worse.

Try a thicker oil if you want more pressure but I'm not a fan of that idea as it will reduce cold starting protection.

wrinx
 
M

·
Guest
Joined
·
0 Posts
Discussion Starter #4
Cheers. If your V6 does it Wrinx then I'm happy with it :)
I'm thinking of changing to 10W60 at the next change. Will give the same protection (hopefully) when cold, but may hide the rattle a bit when hot. I still think the V6 oil gets too hot during "normal" driving.
 

·
Registered
Joined
·
5,002 Posts
I changed to 10W-60 on my 145 to give it a bit more protection when hot :( (there was another thread somewhere recently talking about oil temp, my 145 runs with a water temp of about 90C, so seeingas it only has a water cooled oil cooler I guess the oil temp must be 100C at least! :eek: ) Increasing viscocity is one way to get your oil pressure up, but at the end of the day do you really care about oil pressure? I would have thought that what you want is oil flow, pressure is just a convenient way of indicating flow at a particular viscocity? Any thoughts anyone? :confused:
 
M

·
Guest
Joined
·
0 Posts
Discussion Starter #6
The increase in oil viscosity isn't to get a higher pressure, but to hopefully increase protection when hot. The 12v V6 seems to rattle when hot suggesting to me that the specified 10W40 isn't thick enough when hot. I can get the oil temp to about 100ºC during a breenge :eek: .
Afterwards, the car is starting to rattle like a can of nails. It's quiet when cold though.
 

·
Registered
Joined
·
4,651 Posts
Oil pressure on mine sits at 4 bar when warm at anything over 2000rpm below that it sits at 2 bar and when cold its on 6 bar ...........always has ever since i got it and i chuck any old oil in it :rolleyes:

Even when the oil temp is up around 130 degree`s :eek: after a good razzin ;) :D :D
 

·
Premium Member
Joined
·
1,111 Posts
Oil pressure is a measure of resistance not flow and flow is equally important so bear this in mind when moving to thicker oils.

Thicker oils will give more oil pressure.

Thicker oils handle temperatures better but so do proper synthetic oils where non petroleum basestocks are used.

If you want the best of both world and this is possible you can use a proper 10w-40 or 10w-50 synthetic and this will give you both protection and oil pressure as it doesn't thin down after 2000 miles.

The problem with "hydrocracked" (petroleum based) oils is that they start to thin straight away so what started life as a 10w-60 will be a 10w-30 within a short space of time unlike a synthetic oil which will stay in grade for up to 9000 miles or more. Basically it's the use that makes the difference.

The technical term is "shear stability" and only true synthetics are "shear stable" because the basestocks are more thermally stable to start with and need little or no VI Improvers to prop them up. These important additives are polymers that expand with heat to thicken the oil when hot, unfortunately they are also the weakness in an oil and "shear" causing the oil to lose viscosity.

It's complicated but hopefully this little article explains:

SAE has a test called HT/HS (High Temperature/High Shear) if an oil shears back too much on this high temperature test, it cannot be sold as a multi-grade oil. In fact, the test results from this test are very helpful in indicating the quality of the oil.

The higher the HT/HS number the better because this indicates less shearing. Petroleum oils tend to have low HT/HS numbers which barely meet the standards set by SAE. Because petroleum oils are made with light weight basestocks to begin with, they tend to burn off easily in high temperature conditions which causes deposit formation and oil consumption.

As a result of excessive oil burning and susceptibility to shearing (as well as other factors) petroleum oils must be changed more frequently than synthetics.

Not all multi-viscosity oils shear back so easily. True synthetic oils (PAO’s and Esters) contain basically no waxy contamination to cause crystallization and oil thickening at cold temperatures. In addition, synthetic basestocks do not thin out very much as temperatures increase. So, pour point depressants are unnecessary and higher viscosity basestock fluids can be used which will still meet the "W" requirements for pumpability.

Hence, little or no VI improver additive would need to be used to meet the sae 30, 40 or 50 classification while still meeting 0W or 5W requirements.

The end result is that very little shearing occurs within true synthetic oils because they are not "propped up" with viscosity index improvers. There simply is no place to shear back to. In fact, this is easy to prove by just comparing synthetic and petroleum oils of the same grade.

Synthetics will generally have significantly higher HT/HS numbers. Of course, the obvious result is that your oil remains "in grade" for a much longer period of time for better engine protection and longer oil life.

Cheers
Simon
 
M

·
Guest
Joined
·
0 Posts
Discussion Starter #9
cool thanks. You must be getting bored explaining oil related stuff to us all the time ;)
 

·
Premium Member
Joined
·
1,111 Posts
The general recommendation is for 5w-40 or 10w-40 so it seems fine.

Not sure about the oil quality though as I'm not familiar with this product so I can't comment on the oil itself.

Cheers
Simon
 
J

·
Guest
Joined
·
0 Posts
Discussion Starter #13
So which oil manufacturers use the best/top grade base stocks? and which is the cheap crap that should be avoided.
FGN
 

·
Premium Member
Joined
·
1,111 Posts
Hmm

Bit of a minefield this one as 95% of the oils out there are of the "hydrocracked" variety.

As general guidence, avoid shop brands, cheap oils (there are no bargains I'm afraid) and avoid anything where you cannot get hold of a technical data sheet on the product.

Oils made under licence are made to a budget and therefore tend to be inferior as the good stuff is always expensive.

Oils available in the UK that contain PAO's and/or Ester are

Silkolene PRO S and PRO R (pao/ester)
Fuchs Titan Supersyn (pao)
Mobil 1 (pao)
Motul (pao/ester)
Redline (pao/ester)
Royal Purple (pao/ester)

US oils tend to be expensive and UK brands are just as good and better value.

0w oils contain proper synthetics as petroleum oils are not capable of passing the -35 degC pour tests.

There is some data on some proper synthetic oils here:
http://www.opieoils.co.uk/lubricants.htm

Hope this at least gives some guidance.

Cheers
Simon
 

·
Registered
Joined
·
17,177 Posts
Oilman!!
Thanks for all the technical info!
:cool:

Here's a more basic question...
:eek:
When should you check your oil level?
With the engine hot or cold?
:confused:
Thanks
Rick
 

·
Registered
Joined
·
36 Posts
Oilman, you say the higher the HT/HS the better, so what would a "good" value be? and will it be printed on the side of the bottle?
 

·
Premium Member
Joined
·
1,111 Posts
RicksAlfas said:
Oilman!!
Thanks for all the technical info!
:cool:

Here's a more basic question...
:eek:
When should you check your oil level?
With the engine hot or cold?
:confused:
Thanks
Rick
No problems. The engine should be warm, not hot.

Cheers
Simon
 

·
Premium Member
Joined
·
1,111 Posts
flatfourfun said:
Oilman, you say the higher the HT/HS the better, so what would a "good" value be? and will it be printed on the side of the bottle?
No it won't be on the bottle but you can request these figures from the oil company as all oils that have an API rating will have been tested.

Tested at 150 degC (ASTM D4683)

A typical level would be between 2.9-3.0 cp. Some excellent figures as an example are as follows (these are top end of the scale)

Silkolene PRO S 5w-40 4.07 cp
Silkolene PRO S 10w-50 5.11 cp
Silkolene PRO R 15w-50 5.23 cp

Bear in mind these are top ester/pao fully synthetic oils though!

Cheers
Simon
 

·
Registered
Joined
·
848 Posts
Talk about bringing back the dead, but this is a pretty interesting thread. :)

Does anyone have any info on the base oils used for Selenia Racing 10W60? Is it PAO/ester based or hydrocracked, as I have a feeling it tends to run out of grade from hard use on a 10,000km service interval. I'd love to hear of anyone's experience using 10W50/ or 15W50 fully synthetic PAO/ester-based oils on a Twin Spark.
 

·
Registered
Joined
·
30,171 Posts
I've been using Redline 10W40 (HTHS 4.7) in my 16v TS for many years now.
Their 15W50 is HTHS 5.8

Difficult to get any real info on Selenia Racing 10W60, so I expect it is not Ester based.
 
1 - 20 of 21 Posts
Top