Is it time to change oil viscosity?

[TURBO2]

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?

 

[dynoman]

Same as mine with 10w30 .... 70psi cold -- 18psi hot idle .

 

[THensley]

stay where your at all good

 

[deezdad]

What temp tstat? Stock, 180, 160 ?

 

[TURBO2]

What temp tstat? Stock, 180, 160 ?

160, but it goes beyond that since I put in the front mount intercooler. I have to put in some higher rate cooling fans to fix it.

 

[V6sleeper]

Many dont agree with this but i run Vr1 20/50 in NY summer and 10/40 in the fall/winter for 20 years , with only showing a 3 psi hot idle difference

A front mount will put you over 200 degrees on the streets without good dual fans

 

[deezdad]

Only my opinion but I wouldn't run a thicker oil with that cool of an operating temp especially with the fan upgrade.

 

[KC87]

The manual in my (87) says 5-30. Only used 10-40 from the start.
Back in the day Kenne Bell I would say was the big guru and always used 10-40 and recommended it.
And the 10-40 today is way better then 40 years ago
All those 6.2l engines GM has to recall use 0-20. One of the changes will be to have owners switch 0-40 or perhaps
5-40. Hoping to push it over the warranty.
I guess if you're buying new today you pick your poison and hope for the best.

 

[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?

No, never. Also there's no reason to use a 10w30 when you can use a 5W30. 10w30 will be thicker when it's cold that's what the 10 stands for and you don't need it thicker when it's cold. There's nothing wrong with the oil pressure that you have but if you want to bring it up at hot idol, the thing to do would be to add a high volume oil pump. If you're not using Quaker State full synthetic 5W30 oil, you're not getting all the film strength that you might otherwise get by using this product. There's nothing out there that's better. It's the most important thing to look at when you choose a motor oil. Thicker oils do not have higher film strength and they're harder to flow through tight spaces and oils with zinc do not give them higher film strength. The highest film strength oils on the market have the lowest amount of zinc in them and Quaker State is the best but only full synthetic. If it says anything else on the label like ultra protection or super duper don't buy it and the only way to get a good deal on it is to buy it at Walmart.

 

[Turbo6inKY]

At the risk of devolving the thread into another oil holy war, there is no "best" oil. Which is best depends on your application and how you're using it.

But there are a lot of "good enough" oils, and almost everything in a 5w30 or 10w30 you can buy at a mainline store is good enough for a stock engine with regular (3000 miles or once a year, whichever you hit first) oil changes.

ZDDP is a high pressure additive that only kicks in once the film has failed. Most modern oils swap that out for molybdenum because excessive ZDDP tends to acidify the oil and it starts attacking the parts it's supposed to protect. If you've ever seen a camshaft with pitted lobes that didn't spend time under water, that damage was likely from excessive ZDDP in the oil combined with a too-long change interval.

Start tweaking the valvetrain or racing and things can change radically. I run Motul 300V in mine, because I get stuff really hot and it maintains film strength well past 300 degrees while most other store bought synthetics (including Quaker State's retail products) give up around 250-260. It's also $35 per two liter can, so I pay heavily for the feature.

And to reinforce for the OP, your oil pressures appear fine. Keep using the 10w30 in the summer and 5w30 in the winter like the sticker says. If you're really curious, get an oil sample analyzed. that'll tell you way more than the oil gauge can tell you.

High volume oil pumps just waste horsepower and create additional heat. Unless you've built an engine with enlarged clearances, it's not necessary. if you're looking at adding a HV kit to an old engine to compensate for wear, it's a band-aid. You're better off dropping the pan, inspecting everything, and rolling in a fresh set of bearings assuming the crank's OK.

 

[Ttype6]

At the risk of devolving the thread into another oil holy war, there is no "best" oil. Which is best depends on your application and how you're using it.

But there are a lot of "good enough" oils, and almost everything in a 5w30 or 10w30 you can buy at a mainline store is good enough for a stock engine with regular (3000 miles or once a year, whichever you hit first) oil changes.

ZDDP is a high pressure additive that only kicks in once the film has failed. Most modern oils swap that out for molybdenum because excessive ZDDP tends to acidify the oil and it starts attacking the parts it's supposed to protect. If you've ever seen a camshaft with pitted lobes that didn't spend time under water, that damage was likely from excessive ZDDP in the oil combined with a too-long change interval.

Start tweaking the valvetrain or racing and things can change radically. I run Motul 300V in mine, because I get stuff really hot and it maintains film strength well past 300 degrees while most other store bought synthetics (including Quaker State's retail products) give up around 250-260. It's also $35 per two liter can, so I pay heavily for the feature.

And to reinforce for the OP, your oil pressures appear fine. Keep using the 10w30 in the summer and 5w30 in the winter like the sticker says. If you're really curious, get an oil sample analyzed. that'll tell you way more than the oil gauge can tell you.

High volume oil pumps just waste horsepower and create additional heat. Unless you've built an engine with enlarged clearances, it's not necessary. if you're looking at adding a HV kit to an old engine to compensate for wear, it's a band-aid. You're better off dropping the pan, inspecting everything, and rolling in a fresh set of bearings assuming the crank's OK.

Only one thing you said is true and that is that there are many oils that are good enough but they all cost more than Quaker State full synthetic 5W30 if you buy it at Walmart and none of them have the film strength that Quaker State does.

 

[turbocamino1]

At the risk of devolving the thread into another oil holy war, there is no "best" oil. Which is best depends on your application and how you're using it.

But there are a lot of "good enough" oils, and almost everything in a 5w30 or 10w30 you can buy at a mainline store is good enough for a stock engine with regular (3000 miles or once a year, whichever you hit first) oil changes.

ZDDP is a high pressure additive that only kicks in once the film has failed. Most modern oils swap that out for molybdenum because excessive ZDDP tends to acidify the oil and it starts attacking the parts it's supposed to protect. If you've ever seen a camshaft with pitted lobes that didn't spend time under water, that damage was likely from excessive ZDDP in the oil combined with a too-long change interval.

Start tweaking the valvetrain or racing and things can change radically. I run Motul 300V in mine, because I get stuff really hot and it maintains film strength well past 300 degrees while most other store bought synthetics (including Quaker State's retail products) give up around 250-260. It's also $35 per two liter can, so I pay heavily for the feature.

And to reinforce for the OP, your oil pressures appear fine. Keep using the 10w30 in the summer and 5w30 in the winter like the sticker says. If you're really curious, get an oil sample analyzed. that'll tell you way more than the oil gauge can tell you.

High volume oil pumps just waste horsepower and create additional heat. Unless you've built an engine with enlarged clearances, it's not necessary. if you're looking at adding a HV kit to an old engine to compensate for wear, it's a band-aid. You're better off dropping the pan, inspecting everything, and rolling in a fresh set of bearings assuming the crank's OK.

I’ve had mine over 280 a couple times. This was at a hill climb contest close proximity to Death Valley, and there are times when we’re the hottest place on earth. Car runs like shit .. can't imagine how you would get to 300* unless hot lapping a huge engine? Take an average of film strength, sheer rate and viscosity breakdown tests and QS full synth wins the psi test..nothing being more important than film strength. All coverrd by Rat 540 oil tests. However ,we all know, it can develop oil leaks..been there done that so may not be the best go to for our Buick engines?

 

[THensley]

Some of the best pissing matches are oil topics.
If I need something from Walmart that will cover my ASS ill buy underwear not oil.

 

[TexasT]

I love these oil threads! I know what I use, Many others know what they use and then there are the "what do I use" guys. It is oil and an engine definitely NEEDS it to keep spinning. Next up! oil filters! hahaha

 

[Ttype6]

there is no "best"

Oh yes there is, and it's Quaker State full synthetic 5W30 and it's cheaper than any other oil on the market if you buy it at Walmart. Any other oil you buy has a lower film strength and is costing you more money and any oil that you add a zinc additive to is getting destroyed by that additive. If anyone wants to laugh and scoff and talk about how oil can't possibly be good if you buy it at Walmart when it's the same Quaker State that you buy anywhere else it just cost you less, you're just ignoring the evidence. Oil does not become a better or worse oil depending on where you buy it. If you use any 10w30, 10w40, 20w-50 motor oil, or any oil because it has zinc in it and you believe because you're told over and over again that zinc increases the film strength of that oil and makes it more protective, you're ignoring / refusing to look at the evidence, and your using oil with less film strength that costs more. There are just a very few 10w40 and 20w50 oils that have high amounts of zinc in them and are highly protective but they're not as protective as Quaker State full synthetic and they don't flow as good and cost you more and they rob power.

If you find that you're hot oil pressure is at an unsafe low psi, the proper thing to do is install a high volume oil pump and not switch to a thicker oil which is less protective. High volume oil pumps don't Rob power, high oil pressure does.

If you find that your oil is getting hotter than you would like then you need a oil cooler or a better oil cooler.

 

[Ttype6]

It is oil

Yes, oil is oil is oil as far as the oil in the engine bearings because the bearings are running on a hydroscopic wedge of oil so the bearing cannot touch the journal so it doesn't matter what kind of oil you use for the bearings. It's areas of the engine that are relying on a splash of oil where film strength comes into play and you can't have too much film strength. There's no such thing. There is absolutely, however, such a thing is not enough film strength and a flat tappet camshaft is the first thing that will tell you when you don't have enough.

 

[THensley]

I wonder when Chevy Corvette MercedesBenz And Porsche will be draining the Mobile-1 out of there high end cars and ordering Quaker State from Walmart mart?

 

[Mr.Spool]

here is the science
Film strength is a way to decrease the wear on engine parts!
Thickness is also a way to decrease wear on the engine parts!
The strategy in which thin and thicker can be applied is different inmo.
Any engine builder that's really good will know this.
I personally run mobile 1 15-50 full syn with higher oil pressures.
I race alot in specific conditions and the car can't be always cooled down when your not in control of the race timing.
Also the mobile 1 seems to keep the pressures where my builder wants them and takes longer to visually break down with the methanol fuels I run in the conditions I race in.
With that said.
I have seen many different builds with different builders and based on clearances a high film strength low weight oil will help a specific build and will see lower pressures in general than a thicker oil will.
I've seen bearings come out good both ways.
Pressure after racing or hot days the thicker oil will not drop like a thinner oil will.
Depending on your builder and the way your motor was setup should ultimately determine.

 

[Ttype6]

I wonder when Chevy Corvette MercedesBenz And Porsche will be draining the Mobile-1 out of there high end cars and ordering Quaker State from Walmart mart?

Mobil 1 and Pennzoil and a handful of others make motor oils that have very good film strength and I've already said that. You would be well advised to use those oils but they don't have as much film strength as Quaker State full synthetic and they cost more. If they cost the same as Quaker State full synthetic I would still buy Quaker State full synthetic because it has more film strength. To make the choice even easier it costs less. I don't know how many times I have to say that. Use those oils and you'll be fine you'll just be paying more money.

 

[Ttype6]

here is the science
Film strength is a way to decrease the wear on engine parts!
Thickness is also a way to decrease wear on the engine parts!
The strategy in which thin and thicker can be applied is different inmo.
Any engine builder that's really good will know this.
I personally run mobile 1 15-50 full syn with higher oil pressures.
I race alot in specific conditions and the car can't be always cooled down when your not in control of the race timing.
Also the mobile 1 seems to keep the pressures where my builder wants them and takes longer to visually break down with the methanol fuels I run in the conditions I race in.
With that said.
I have seen many different builds with different builders and based on clearances a high film strength low weight oil will help a specific build and will see lower pressures in general than a thicker oil will.
I've seen bearings come out good both ways.
Pressure after racing or hot days the thicker oil will not drop like a thinner oil will.
Depending on your builder and the way your motor was setup should ultimately determine.

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.