Stp and oil viscosity

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Now I know many, probably most of you have no use for Stp oil treatment. But I still would like to know if I were to put one 15 oz bottle in 4 quarts of 10w30 conventional or semi synthetic oil, what would the equivalent viscosity of the mix be. Approximately, not precisely. Would it be like a 15w40, a 20w50, or something odd like a 15w 35????
 
The viscosity would be 10w30, with a gob of STP floating in the pan. Many tests on YouTube show that STP does not dissolve/mix in oil, so it would have no way of affecting the viscosity.
 
It absolutely is miscible in oil.

15 oz. of that product to 4 quarts should still be an SAE 30 unless the starting viscosity of the 10W-30 was at the upper range of the spec. In that case it would be a low SAE 40.
 
So you are saying that adding approximately 12% of a product with as high of a viscosity as STp oil treatment will barely affect the viscosity of the original oil. What if I added one quart of 20w50 oil to the same 10w30??
 
I'm not as critical as others on the site. Years ago, when cars had Oil Pressure Gauges, my cars would sometimes show very low pressure. Especially at idle. One (blue) bottle of STP would fix that. If I would ever see my pressure lamp flicker, I'd have no problem adding any from the blue bottle. (The red bottle and the black bottle are different - I think one has more ZDDP and the other has more cleaning additives).

BTW; it mixes with your oil, no problems, and IT DOES NOT CLUMP.
 
Originally Posted By: MotoTribologist
It absolutely is miscible in oil. 15 oz. of that product to 4 quarts should still be an SAE 30 unless the starting viscosity of the 10W-30 was at the upper range of the spec. In that case it would be a low SAE 40.
You're right. http://www.widman.biz/English/Calculators/Mixtures.html and put in 200 cSt for STP at KV100. I used a KV100=11 cSt for the 10w30, middle of the 30 range. 15 oz is about 11% there. I got 12.9 cSt for the mixture, which is barely thick enough to be a 40 weight. Therefore, I predict you'd get a lighter version of a 10w40 out of your experiment, almost a thick 10w30.
 
This post caught my attention because I tested this exact thing in the Mechanical Engineering Lab at the University of Idaho when I was a student there 50 years ago. The oil pressure gauge that I installed on my 57 Ford read only a few PSI at hot idle so I added 1 quart of STP. The hot idle oil pressure then went up to 20 PSI so I felt much better, but then started wondering how it would perform in cold weather. The Lab had a Saybolt Universal Viscosity tester that timed the oil flow through a capillary tube at 210F and at 100F. The used 10W-30 oil with STP taken from my car tested in the 20W-50 viscosity range. I have always wondered how the HTHS (high temperature, high shear) viscosity and the cold cranking temperature would have responded but those more important measures of viscosity were not tested in those days.
 
Or it would move it up to an SAE 40 or just a slightly higher SAE 30 as already shown in two previous posts.......
 
A consumer reports 1996 According to a 1996 test conducted by Consumer Report , adding STP made a 10w30 more like a 15w40 oil. Granted that was 22 years ago so maybe STP is different now, but that is what STP formulation did back then.
 
STP has stated that the 'goal' of their product is to raise the oil it is being added to by one viscosity grade.

Their example is it would turn a 10W-30 oil into a 15W-40 oil.

When I have seen UOA's where STP has been used, this is what I have seen - the oil is close to the next viscosity grade (some shearing occurs, so it is closer to the line between two grades.

I think in this day and age of severe fuel dilution in small, high-strung engines STP is just the thing to bring oil back to 'where its supposed to be'.
 
Originally Posted By: addyguy
I think in this day and age of severe fuel dilution in small, high-strung engines STP is just the thing to bring oil back to 'where its supposed to be'.
One possible problem with that: STP used Group I or II base oils, prone to oxidation in high-strung engines, and the VII chemicals in there have been said to be low-quality types as well. This could lead to extra piston deposits and varnish. Using just a little in a well-formulated full synthetic oil shouldn't be a problem since it'll mix with the oil's powerful anti-oxidant package and dispersants. .... I think.

Instead, amazon order some Schaeffers Moly E.P. Oil Treatment, at KV100=238 cSt, its thick and likely has better components. It contains antimony and organic components, with very little other unnecessary stuff. Thickener for sure.
 
...or STP's new 'Synthetic' Oil Treatment in the gold bottle.

Has lots of goodies the 'regular' blue-bottle doesn't - detergents and antioxidants.
 
My 08 Subie with the 2.5 turbo motor likes the grey bottle (high mileage formula with extra ZDDP) I just put a bottle in this weekend on top of my Maxlife 5W30 and within a few miles noticed the engine was much quieter! The high mileage (150k) and the turbo really beat the oil up, a little more Viscosity IMO is a good thing.
 
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