Is it time to change oil viscosity?

[Ttype6]

I have a 1986 GN with around 108,000 miles on it. I'm using the factory suggested 10w-30 and have about 70 psi oil pressure when cold, but once it heats up the pressure drops to only about 17-18 psi. Should I switch to 10w-40 or 20w-50?

I don't know what oil you're currently running but I do know two things about it, it's much more expensive than Quaker State full synthetic 5W-30 when purchased at Walmart and it has less film strength. It's a no-brainer. Perhaps you're concerned about running a synthetic oil and having it cause an oil leak and that is a real concern. In that case, you might be interested in Quaker State all mileage 10w 40. It has an impressively high film strength of over 126,000 PSI and it's a conventional oil. It has the highest PSI strength of any conventional oil that 540 rat has tested to date. I don't recommend that you run a thicker oil, I recommend you run Quaker State 5W30 full synthetic. But I do understand there are some concerns about oil leaks.

 

[LANDAU LIMITED]

If you want to base your oil choice on some guy on the internet rubbing ball bearings together so be it. He's also the same guy who said if you run Quaker State you don't need to break in a flat tappet cam. Just fire it up and go with no break in lube on the cam. I just picked up a voodoo cam for cheap I'm thinking of trying that. If it works I'll jump on the 540rat bandwagon, until then I'm skeptical.

 

[turbocamino1]

If you want to base your oil choice on some guy on the internet rubbing ball bearings together so be it. He's also the same guy who said if you run Quaker State you don't need to break in a flat tappet cam. Just fire it up and go with no break in lube on the cam. I just picked up a voodoo cam for cheap I'm thinking of trying that. If it works I'll jump on the 540rat bandwagon, until then I'm skeptical.

Interesting take ..it is a very very long read..curious how much you read? Tests are test..they have results..some methods are more definitive than others .. deny all you like..but rocks are hard and water is wet. Some things ARE surely fact.

 

[LANDAU LIMITED]

Interesting take ..it is a very very long read..curious how much you read? Tests are test..they have results..some methods are more definitive than others .. deny all you like..but rocks are hard and water is wet. Some things ARE surely fact.

I've been watching 540Rat go back and forth with many people over the last 20 years on many different forums. I've also read a ton of literature he has written. I just take it with a grain of salt, I actually use one of the higher rated oils on his list. I REALLY want to test his theory on flat tappet break in just for grins.

 

[Mr.Spool]

Again, that's not to say that you can't get a thick oil that has high film strength but you can't attribute its film strength to the viscosity, it's attributed to the additive package

So you don't believe viscocity

Engine builders and doctors like the rest of us are human beings and the thing that Hitler learned from Lennon is that a lie told often enough becomes the truth and we are all susceptible to that. Engine builders believe the same wives tales that most all of us do. Thick oils do not protect engine parts better than thin oils. Film strength is what does that and the higher that it is the more protection you have. They do allow the oil pressure to stay higher at hot idle but again if your oil pressure comes below something that you're comfortable with that's when you need a high volume oil pump. There's another thing that most all thicker oils tend to have in common and do better generally speaking than thinner oils and that is that they tend to have a typically much higher temperature at which the onset of thermal breakdown starts to occur. There is also a third thing that I can think of that thick oils consistently do better than thin oils and that is that when you run a thicker oil, the engine will burn less oil. Oil pressure, thermal breakdown, and oil consumption are the only three things that improve when you use thicker oils and they improve just about every time. Film strength is not improved by higher viscosity nor is it improved by zddp and the common myth is that both of those things improve film strength but it's just not true. Again, that's not to say that you can't get a thick oil that has high film strength but you can't attribute its film strength to the viscosity, it's attributed to the additive package. There's no reason why thicker oils couldn't be some of the most protective oils but in real life when you measure their film strength most all of them fall short except for one, amsoil 10w50 dirt motorcycle oil which has a film strength of 134,968 PSI and is the number six oil in 540 rats oil film strength list. The number 11 highest strength oil is Quaker State full synthetic 5W30 with a PSI reading of $133,302. The next highest 50 weight motor oil on the list comes in at number 35 and it's amsoil signature series synthetic 5w50 with a PSI strength of 118,543. In the 249th position on his list is mobile one synthetic 15w50. I don't know if this is the same one that you use but it has a film strength of 70,235 PSI and that's not good. And of course the 10w50 amsoil dirt motorcycle oil is 18 or 19 dollars a quart. It will do all the things that a thick oil does for you currently but it also has incredible film strength.

Viscosity also determines film strength by the thickness
Your saying its not (unless thats a typo).
That alone effects the protection especially in the heat.
Which I believe is how these 15/20 50s oils are recommended for.
Not just extreme pressures but for heat as well

 

[Mr.Spool]

Again, that's not to say that you can't get a thick oil that has high film strength but you can't attribute its film strength to the viscosity, it's attributed to the additive package.

Think this is where people get hung up.
The additive package is the way to get higher on the vi scale that's why Dino oil has a lower number than a synthetic from how I understand it.
Think the hangup is where you don't believe viscocity increases film strength.
Thicker oils create a thicker film strength is how I understand it
I could be wrong but there are plenty of sources that acknowledge this relationship.
I feel I am no oil expert just throwing it out there
I've used alot of different oils over the years and I don't use high end fancy anymore the Walmart stuff works on big power.
The pure methanol cars do run the special green stuff lol and its far from cheap

 

[Mr.Spool]

higher viscosity

The engines resistance to flow is supposed to play a key role.
That's also why I run the 15/20w 50 oil

 

[Turbo6inKY]

The pure methanol cars do run the special green stuff lol and its far from cheap

Methanol draws in water and it gets really corrosive, and most pure-methanol builds run REALLY rich, so a lot of it ends up in the oil. It takes a special additive package to manage that.

 

[Mr.Spool]

Methanol draws in water and it gets really corrosive, and most pure-methanol builds run REALLY rich, so a lot of it ends up in the oil. It takes a special additive package to manage that.

I get it
I've lived it