Discussion
while reading the thread about a new cam fitted twas mentioned "which oil is best" fully or semi so whats everyones opinion? mine did have mobil1 15/50 and the oil pressure stayed nearly the same hot or cold but then I changed to vavoline semi and when it gets hot the pressure drops to 35psi. so can the semi not handle the temps aswell?
IMHO, people worry slightly too much about oil pressure. So long as the hot idle pressure is above approximately 20-30 with a reasonably accurate sender (see threads passim about replacing oil pressure senders) then you've nothing to worry about.
Arguably, pressure and flow are opposites. If your gauge is showing high pressure, that means that your oil is making it more difficult for the pump to push the oil around due to its viscosity. So high pressure is not necessarily better than moderate pressure - although obviously low pressure is not desirable.
In my experience the oil pressure is quite sensitive to the oil's viscosity. My pressure used to read about 40-45 psi at hot tick over, running a 10W/50 full-synthetic. It's just had a service at which they used a 10W/40 semi, and the pressure now shows about 35 psi on hot tick over (although the cold pressure is about the same). That makes sense, because the new oil's hot viscosity rating is lower, but its cold rating is the same.
I use the oil pressure gauge as an indirect temperature indicator. When I see that the idle pressure has dropped, I know the oil has warmed up.
Arguably, pressure and flow are opposites. If your gauge is showing high pressure, that means that your oil is making it more difficult for the pump to push the oil around due to its viscosity. So high pressure is not necessarily better than moderate pressure - although obviously low pressure is not desirable.
In my experience the oil pressure is quite sensitive to the oil's viscosity. My pressure used to read about 40-45 psi at hot tick over, running a 10W/50 full-synthetic. It's just had a service at which they used a 10W/40 semi, and the pressure now shows about 35 psi on hot tick over (although the cold pressure is about the same). That makes sense, because the new oil's hot viscosity rating is lower, but its cold rating is the same.
I use the oil pressure gauge as an indirect temperature indicator. When I see that the idle pressure has dropped, I know the oil has warmed up.
Dr Mike Oxgreen said:
Arguably, pressure and flow are opposites. If your gauge is showing high pressure, that means that your oil is making it more difficult for the pump to push the oil around due to its viscosity. So high pressure is not necessarily better than moderate pressure - although obviously low pressure is not desirable.
That's a bit of a raving rant IMHO.Pump pressure goes up, flow WILL increase.
Higher viscosity means oil will be 'sticking' / staying more exactly where it is NEEDED.
Good flow might just make all the oil pee out into the rocker covers... up the flame trap, in the plenum, down the valve guides....
Trying to justify ones own cars characteristics & mods seems to be getting endemic on here, and common sense is going off site.
Viscosity is about how easily a fluid flows, or in other words: viscosity is the resistance to flow. Here's the definition of viscosity. So I'm not sure how my statement that viscosity and flow are "opposites" constitutes a rant, but hey.
Whether you put a 40-weight oil in your engine or a 50-weight oil in, it won't make much difference to the rate of flow that your pump is pumping. But it will make a measurable difference to the oil pressure: the higher viscosity oil will exert a greater resistance, and this manifests itself as pressure.
But as I say, so long as your oil pressure gauge is pointing roughly in the middle, you really have nothing to worry about.
Whether you put a 40-weight oil in your engine or a 50-weight oil in, it won't make much difference to the rate of flow that your pump is pumping. But it will make a measurable difference to the oil pressure: the higher viscosity oil will exert a greater resistance, and this manifests itself as pressure.
But as I say, so long as your oil pressure gauge is pointing roughly in the middle, you really have nothing to worry about.
Edited by Dr Mike Oxgreen on Wednesday 21st March 14:54
Dr Mike Oxgreen Originally said:
Arguably, pressure and flow are opposites.
Dr Mike Oxgreen then says he said:
So I'm not sure how my statement that viscosity and flow are "opposites" constitutes a rant, but hey.
Do you actually know what you are saying / typing, if you don't we won't stand much chance of guessing what you are printing vs what might be in your mind?ETA: OP target 10psi per 1000rpm ~ it all depends how hot (heat & power) your engine is, the clearances... Attempting to keep stable oil pressures with demanding temps & oil that retains its working properties whilst still keeping the internals golden (rather than black s
te) is to say the least a challenge. Personally I wouldn't use anything but good quaility synthetics.Edited by spend on Wednesday 21st March 15:34
Apologies, the first one should have said: "viscosity and flow". I'm sure you've made mistakes yourself in the past, spend. 
But, as I say, high viscosity and high pressure go hand-in-hand - so what I said wasn't far off the truth.
Edited to add: I'd be interested to know how you justify saying that high viscosity means oil sticks where it's needed. It really doesn't imply that at all.
But, as I say, high viscosity and high pressure go hand-in-hand - so what I said wasn't far off the truth.
Edited to add: I'd be interested to know how you justify saying that high viscosity means oil sticks where it's needed. It really doesn't imply that at all.
Edited by Dr Mike Oxgreen on Wednesday 21st March 15:42
spend said:
Dr Mike Oxgreen Originally said:
Arguably, pressure and flow are opposites.
Dr Mike Oxgreen then says he said:
So I'm not sure how my statement that viscosity and flow are "opposites" constitutes a rant, but hey.
Do you actually know what you are saying / typing, if you don't we won't stand much chance of guessing what you are printing vs what might be in your mind?
He's on the blob again
Told me last week my car was going to burn down cos I fitted a new starter lead
It's just f
king oil after all, not worth throwing a Paddy over is it now 
Lovely bloke no doubt and an encyclopaedic knowledge for sure, but a bit of therapy to bring the happiness up wouldn't go amiss
I know all about viscosity ! my mate mixes hydrolic oil and diesel togther and runs it in his old van ..He mixes it then times it flow down a board ..Im not joking !
Thats where 20 and 60 second heating oil comes from ..
I surppose you have to loose your anger somewhere..
Got to say he is a Bee Hive of Knowledge and a real gent in flesh .
Well i have been told that .
Right im going to take his avice and start useing synthetic
Just changed my oil VR1 mineral it was black ,thats in 3000 miles.
http://www.fluidsinmotorsport.co.uk/index.html#Qua...
Thats where 20 and 60 second heating oil comes from ..
I surppose you have to loose your anger somewhere..
Got to say he is a Bee Hive of Knowledge and a real gent in flesh .
Well i have been told that .Right im going to take his avice and start useing synthetic
Just changed my oil VR1 mineral it was black ,thats in 3000 miles.
http://www.fluidsinmotorsport.co.uk/index.html#Qua...
Edited by SILICONEKID340HP on Wednesday 21st March 16:44
Edited by SILICONEKID340HP on Wednesday 21st March 16:46
My VR1 is still like new after 3000 miles my only concern was the slight drop in pressure when hot which the fully didn't but I don't think it's a problem. Reading old threads alot of people sway towards semi as they are old engines and something to do with zinc I think. I'm just after some opinions of peoples thoughts and I will make a decession then thanks
Twistygit said:
My VR1 is still like new after 3000 miles my only concern was the slight drop in pressure when hot which the fully didn't but I don't think it's a problem. Reading old threads alot of people sway towards semi as they are old engines and something to do with zinc I think. I'm just after some opinions of peoples thoughts and I will make a decession then thanks
Think im going to try one of these three ..Morris 15w50 Mineral https://shop.fluidsinmotorsport.co.uk/product/morr...
High in zinc
Millers semi 20w60 https://shop.fluidsinmotorsport.co.uk/product/css2...
Penrite semi 15w60 http://www.holden.co.uk/displayproduct.asp?sg=&...
Plenty of opinions on which oil is "best" I tend to try different ones when its oil change time and form my own opinions.
Having a trial with this mobil fully syn 10w 60 at the moment and i am very impressed. Oil pressure stays within 10 psi from cold to hot[ [this is probably due to the new cheap ebay oil presure sender, which is much more accurate]
http://www.mobil.co.uk/UK-English-LCW/carengineoil...
Having a trial with this mobil fully syn 10w 60 at the moment and i am very impressed. Oil pressure stays within 10 psi from cold to hot[ [this is probably due to the new cheap ebay oil presure sender, which is much more accurate]
http://www.mobil.co.uk/UK-English-LCW/carengineoil...
SILICONEKID340HP said:
Morris 15w50 Mineral https://shop.fluidsinmotorsport.co.uk/product/morr... High in zinc
Millers semi 20w60 https://shop.fluidsinmotorsport.co.uk/product/css2...
So which one of these 2 is the best to get ??Millers semi 20w60 https://shop.fluidsinmotorsport.co.uk/product/css2...
Pink_Floyd said:
SILICONEKID340HP said:
Morris 15w50 Mineral https://shop.fluidsinmotorsport.co.uk/product/morr... High in zinc
Millers semi 20w60 https://shop.fluidsinmotorsport.co.uk/product/css2...
So which one of these 2 is the best to get ??Millers semi 20w60 https://shop.fluidsinmotorsport.co.uk/product/css2...
Pentrite has a good name ,now doing a fully synthetic 15w60
If you go on the Australian V8 forums they go mad for Penrite.
Morris is a good oil they do a 10w50 fully synthetic available at a good price from Partco.
The 15w50 mineral has just be blended to be in direct compitition with Valvoline VR1 20w50 Racing oil.
Morris 15w50 has more Zinc content than VR1
What attracts me to the Morris 15w50 Mineral is its a good price and plenty of Zink and i prefer the 15 rather tahn 20..
https://shop.fluidsinmotorsport.co.uk/product/morr...
If you go on the Australian V8 forums they go mad for Penrite.
Morris is a good oil they do a 10w50 fully synthetic available at a good price from Partco.
The 15w50 mineral has just be blended to be in direct compitition with Valvoline VR1 20w50 Racing oil.
Morris 15w50 has more Zinc content than VR1
What attracts me to the Morris 15w50 Mineral is its a good price and plenty of Zink and i prefer the 15 rather tahn 20..
https://shop.fluidsinmotorsport.co.uk/product/morr...
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