Top off with a heavier oil for 0w-20?

[Hohn]

For an already thin oil like 0w-20 would it make sense to top it off with something heavier, like 0w-30 or 0w-40, to make up for the fact it's thinning as you get closer to your OCI? If an engine takes 4 quarts and you have to top it off with 0.5 quarts, would you choose 0w-30 or 0w-40 to help bring it back closer to its viscosity when it was new? Let's say the OCI is 10K miles on engines with low tension rings.

None of this makes sense as a baseline condition. Why would you push an oil to 10k OCIs if you believe it's shearing excessively?

Isn't the obvious thing to drain the oil before it's sheared excessively? Or run a higher grade oil that is capable of meeting 10k OCIs in grade?

Or running a thicker grade oil to budget for the expected shear?

Either the shearing is concerning enough to drive the shorter OCIs or it isn't. If it isn't, then just stop off as normal. If it is, don't run 10k OCIs.

 

[Urshurak776]

My cars typically take a touch over 5 quarts, so I add that bit "extra" with whatever I have lying around. API SP oils are compatible with each other, so not going to harm anything. Certainly not ideal, but won't hurt anything.

 

[kschachn]

None of this makes sense as a baseline condition. Why would you push an oil to 10k OCIs if you believe it's shearing excessively?

Isn't the obvious thing to drain the oil before it's sheared excessively? Or run a higher grade oil that is capable of meeting 10k OCIs in grade?

Or running a thicker grade oil to budget for the expected shear?

Either the shearing is concerning enough to drive the shorter OCIs or it isn't. If it isn't, then just stop off as normal. If it is, don't run 10k OCIs.

And here there’s no evidence being presented that the oil is thinning due to mechanical shear of the VM. In fact there’s no evidence any oil is thinning by any means.

 

[ARCOgraphite]

... Unless I knew for sure that the 0W-30 and 0W-40 variant of that specific oil brand and series uses the same additive chemistry, I wouldn't bother. ... .

Good advice.

My new Subaru came with 0W-16, I would likely not top off with anything other than this low HTHS lubricant that relies more than ever on the additive package to perform adequately.

Hopefully I will not have to add, as I likely cannot obtain the FF Idemitsu chemistry stateside - just the dealer parts counter stuff from Idemitsu Lubricants in Indiana. Maybe it's the same juice.

I was nonplussed with the last Subaru Genuine 0W-20 I ran in the Wife's '23 Crosstrek. Odd as it has been stellar each time in the past. I Do not recall if it was API SN or SP.

 

[Jetronic]

Thanks. Knowledge sponge here.
Very good point. I live where it never gets cold so I forget that aspect

Just to be clear then....using 10w-30 in an engine calling for 0w-20 would cause no problems ?

Did anyone call for me?

using 10W-30 in my ecotec that calls for 0W-20

 

[Shel_B]

You didn't mention the year of the vehicle but most newer cars have thinner rod bearings and main bearings than years ago (in my day).
The tolerances are also tighter. All designed to cut down on CO2 emissions. If you use too thick an oil in newer engines it can actually result in lubrication starvation.

This is what I've gathered from reading a lot of forums on auto repair anyway.
Can't guarantee the validity.

Oh, I see this has already been addressed. Good for you. We're all learning.

 

[tcp71]

Other than the Macan, there isn't a vehicle in my signature list that is using the prescribed oil. they range from 9 to 20 years old. All of them run like a top. The sienna is closest, but even that has been "back certified" for 0w20.

 

[kschachn]

Other than the Macan, there isn't a vehicle in my signature list that is using the prescribed oil. they range from 9 to 20 years old. All of them run like a top. The sienna is closest, but even that has been "back certified" for 0w20.

It helps when you start to understand that what’s in the owner’s manual is a recommendation.

 

[live_to_hunt]

I have Rotella 10w30 in the garage that’s what I run in the lawnmower, snowblower, generator etc. if my Tundra is ever low on oil I top it off with the Rotella