5W-40 All year round?

[Swift101]

I'll see how things work out with 5W-40. If my fuel economy takes a big hit and the UOA results comes back poor then I won't use it.

My logic for using a heavier oil is to extend my OCI past 3.5K, preferably go to 5K (max allowed by Hyundai). I've seen many reports showing products like PP 5W-30 shear out of grade after 3200 miles. I know shearing might not hurt anything but I'm sure it's not ideal.

 

[Kuato]

Originally Posted By: Swift101
I may just keep my car on 5W-40 all year round if analysis yields good results.

It should offer the same protection as 5W-30 since they are both 5W oils right?? Just want to be sure I'm not missing something.

I did search the forums but saw some mixed results on what to use during the winter.



5w cold weight is 5w cold weight. No worries.

 

[Garak]

Originally Posted By: Gokhan
It depends on how you do the experiment. I compared them under almost identical conditions and driving, using the same gas pump.

I have already posted somewhere on the board the rationale as to why I don't accept error bars of less than 10% on fuel economy calculations. And, I assure you that my reasoning is mathematically rigorous.

A 7% difference could be considered plausible. And I don't doubt you saw such a difference back to back. Heck, I saw some impressive differences on return trips because of switching from a headwind to a tailwind.

But, those observations are not mathematically rigorous. Differences do exist, but for us to think we can accurately measure them through normal usage is folly.

 

[Shannow]

Like this...is why I stopped bothering trying to figure it out...

And 90% of my fuel was bought at the same pump, at the same station each time.

 

[supercity]

Originally Posted By: A_Harman
Originally Posted By: Shannow
Specific heat of oil is pretty well a constant...pumps are positive displacement...how does a thinner oil move more heat ?

Just asking...


Thinking about the environment inside of an oil cooler:
Lower viscosity means higher Reynolds number --> better convective heat transfer.


Maybe not, since the velocity is the same, if the flow regime remains the same then it wont matter as convection is not a limiting factor.

 

[CATERHAM]

Originally Posted By: Swift101

My logic for using a heavier oil is to extend my OCI past 3.5K, preferably go to 5K (max allowed by Hyundai). I've seen many reports showing products like PP 5W-30 shear out of grade after 3200 miles. I know shearing might not hurt anything but I'm sure it's not ideal.

And your reasoning is entirely flawed.
Firstly, Hyundai doesn't even specify that synthetic oil be used, so electing to use a premium synthetic which is clearly more shear stable than the most shear prone API dino gives you an increased viscosity margin.
Secondly, it's not oil shear that you have to be all that concerned about to warrant running a heavier grade but rather very high oil temp's, and since you're not tracking your car extreme oil temp's aren't going to happen.
Finally, even a shear prone 5W-30 will still provide plenty of viscosity reserve. You're making the common newbie error that it won't, in effect second guessing the engineers, and therefore blindly assuming running a heavier grade will provide a lubrication advantage when the reality is the opposite.

The best approach one can take for a street driven car is to run the lightest oil specified for the engine and if a synthetic oil is not specified then use one for additional high temp' protection plus other benefits.
If you're serious about high performance driving then install oil gauges which will enable you fully monitor the operational viscosity of the oil you're running. In so doing, more often than not you'll find that a lighter oil grade than specified will often work optimally and very rarely a heavier oil grade even with track use.

 

[StevieBoy]

I'd use M1 0W-40 and go for 10K+ mi. OCI's. My 2 cents.

 

[A_Harman]

Originally Posted By: CATERHAM
Originally Posted By: Swift101

My logic for using a heavier oil is to extend my OCI past 3.5K, preferably go to 5K (max allowed by Hyundai). I've seen many reports showing products like PP 5W-30 shear out of grade after 3200 miles. I know shearing might not hurt anything but I'm sure it's not ideal.

And your reasoning is entirely flawed.
Firstly, Hyundai doesn't even specify that synthetic oil be used, so electing to use a premium synthetic which is clearly more shear stable than the most shear prone API dino gives you an increased viscosity margin.
Secondly, it's not oil shear that you have to be all that concerned about to warrant running a heavier grade but rather very high oil temp's, and since you're not tracking your car extreme oil temp's aren't going to happen.
Finally, even a shear prone 5W-30 will still provide plenty of viscosity reserve. You're making the common newbie error that it won't, in effect second guessing the engineers, and therefore blindly assuming running a heavier grade will provide a lubrication advantage when the reality is the opposite.

The best approach one can take for a street driven car is to run the lightest oil specified for the engine and if a synthetic oil is not specified then use one for additional high temp' protection plus other benefits.
If you're serious about high performance driving then install oil gauges which will enable you fully monitor the operational viscosity of the oil you're running. In so doing, more often than not you'll find that a lighter oil grade than specified will often work optimally and very rarely a heavier oil grade even with track use.


I think that swift's concern is fuel dilution in a GDI engine that will cause viscosity loss. So he wants to start out thick and be sure that the oil stays at least a 30 weight at the end of the OCI.

 

[Swift101]

Quote:
I think that swift's concern is fuel dilution in a GDI engine that will cause viscosity loss. So he wants to start out thick and be sure that the oil stays at least a 30 weight at the end of the OCI.


That's exactly right, I'll send in a sample when I change my oil and post the results.

Thanks everyone for your suggestions.

 

[CATERHAM]

And you think the engineers didn't factor fuel dilution into their viscosity recommendation?
So you have a UOA done and the oil has a KV less than 9.3cSt. So what? That doesn't mean the oil is too light. Concluding that it is, again, is just second guessing the engineers with no real valid point of reference. All manufactures allow a high degree of viscosity loss before an oil is condemned. The best and only practical tool to determine in real time that an oil may be too light is with the use oil gauges, that's because you're measuring actual operational viscosity which gives one the net affect of shear, fuel dilution and oil temperature.

 

[Merkava_4]

Originally Posted By: Gokhan
Moreover, 5W-40 will put unnecessary strain on your oil pump at all temperatures.

 

[Volvohead]

Swift101, if the engine is still under warranty and the manufacturer is recommending 5w-40 for improved vehicle performance, use what the manufacturer recommends. They know more about their engine than anyone else does and won't recommend that viscosity without due reason.

You can run 5w-40 here in the mid-Atlantic year-round. We ran it in our 855 for years, summer and winter, and it's still going strong at over 260k and counting (now with its new owner).

 

[Swift101]

I'm not second guessing the engineers, I'm sure they do an excellent job. I'm only trying to determine which grade offers the best protection for my engine. Not to mention, engineers don't always make the final call. You have to consider the recent problems Hyundai had regarding MPG claims.

It's quiet possible upper management at Hyundai is pushing their engineers to come up with better MPG numbers. After all Hyundai is still a budget oriented brand, one of their main selling points is fuel efficiency. There push for 5W-30 could be purely based on fuel efficiency. After all the warranty is up at 100K, if engine trouble occurs after that period it becomes the consumers problem.

My theory could be completely wrong and I hope it is. Just food for thought.

I'll have both 5W-30 & 5W-40 oils analyzed several times.

If the reports come back good for both weights, then I'll stick with a 30 weight oil. But if the 40 weight oil yields better results then I may consider using it exclusively.

 

[Shannow]

So....the "engineers" got it right when they specify a light oil, meaning that you should never second guess them and go heavier, as they covered all the bases in their recommendation.

But they got it wrong, in that you can always (in general) go lighter than their recommendation...

So are the engineers right, or wrong ?

Or are they only wrong when they specify 30 or higher ?

 

[Clevy]

Originally Posted By: Doug Hillary
Hi,
OVERKILL - I for one share that sentiment!


Count me in on that deal.

As JAG posted above I too enjoy your posts and think you are an asset to this forum OVERKILL. You post very concise,well written and very informatively and I for one consider that due to one member we lose a fantastic contributor such as yourself.

Many of us here have different opinions and viewpoints however we seem to get along pretty well even with those different points of view.

Turt is certainly inflammatory and standoffish and contributes nothing of value in my opinion.
I've got the guy on ignore,and him alone. I enjoy reading every post,even if I don't agree.

 

[wemay]

Originally Posted By: CATERHAM
And you think the engineers didn't factor fuel dilution into their viscosity recommendation?
So you have a UOA done and the oil has a KV less than 9.3cSt. So what? That doesn't mean the oil is too light. Concluding that it is, again, is just second guessing the engineers with no real valid point of reference. All manufactures allow a high degree of viscosity loss before an oil is condemned. The best and only practical tool to determine in real time that an oil may be too light is with the use oil gauges, that's because you're measuring actual operational viscosity which gives one the net affect of shear, fuel dilution and oil temperature.


They recommend both xw30 and xw40 for the Sonata, not just the 30. Actually, the verbage used for the xw40 is along the lines of, ' for better performance...'

 

[Swift101]

Quote:
They recommend both xw30 and xw40 for the Sonata, not just the 30. Actually, the verbage used for the xw40 is along the lines of, ' for better performance...'


+1

I appreciate everyone's input, I know there's a lot of opinions on which weight is better.

I don't want this thread to carry on forever, I'm just doing to do some of my own amateur testing with the 2 approved oil weights.

 

[CATERHAM]

Originally Posted By: wemay


They recommend both xw30 and xw40 for the Sonata, not just the 30. Actually, the verbage used for the xw40 is along the lines of, ' for better performance...'


Well that's a misquote if I've read one.
A heavier grade for "better performance".

 

[Garak]

Originally Posted By: CATERHAM
A heavier grade for "better performance".

Better protection is somewhat plausible, at least under select circumstances. Heavier for better performance, though? I don't think so.

 

[wemay]

Dont kill the messenger... that's what it says, ' for better vehicle performance'. Check the recommendation print screen posted earlier in this thread. Page Two.