Do engine oil additives actually work? (aftermarket ones)

The Walmart branded stuff, not everything else on the shelf.
Oh and “both carry the same service logo's and special service letters that the engine calls for” as you said?

And it’s “logos” not logo’s. I thought you had both a degree in nucular engineering and a law degree from Harvard? Didn’t they teach you proper punctuation at either place?
 
The question is, how would you know? Because some guy that sounds smarter than the others answered the question? 🎪
 
I have used MMO as an oil additive (replacing 1 quart) as I thought it would help with additional cleaning of a higher milge vehicle . The result was inconclusive ... However I have used Rislone High Mileage (16 oz. bottle) and was happy with the results to clean / cure a sticky valve . *Using a good synthetic oil and oil filter at lower oil change intervaals seems to be the better ply long term for most anything you are trying to cure or improve in an engine .
 
I tried some Lubeguard Bio-Tech this last go around...

Oil filter_9-21-2020.JPG
 
It seems to be a light viscosity and the this motor just about lives @ 7500 RPM. I have a thread with all reports on it in the powersports section. I do question B-S methods of fuel however.
 
It seems to be a light viscosity and the this motor just about lives @ 7500 RPM. I have a thread with all reports on it in the powersports section. I do question B-S methods of fuel however.

You can get a better idea by finding the virgin FP for the lube and comparing it to what they are showing as I think Blackstone just "wings it". If this is the AMSOIL Marine 10w-40, the FP is 464F, so it has dropped ~80F, which is reasonably significant.

Using a visc calc, let's use a visc for gasoline of 0.550cSt. The visc for your 10w-40 virgin was 14.1cSt:

I end up with 89% 14.1cSt, 11% 0.550cSt to get to where your viscosity ended up so around 10-11% fuel dilution.
 
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