It's a fact that most 5w30s shear down to 5w-20, sometimes in as little as 500 miles. Does that also mean the HT/HS viscosity is lowered as well? Does anyone have definitive evidence of what happens to the HT/HS viscosity over an oil change interval?
5w-30 and shearing
- Thread starter Drew99GT
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Yet to hear what, that 5w30s shear??? Go look at the first 10 or so UOA; there is a Schaffers 5w30 with 800 miles that is 8.5Cst and a Pennzoil 5w30 with 900 miles that's lower than that!
If 5w30s shear down really badly then maybe it is time to think in terms of synthetic oil all the time. Surely Mobil 1 5w30 will not shear down too badly, will it? After all, most new cars and trucks in the USA require either 5w30 or 5W-20 motor oil. If these oils are going to thin out dangerously in only a few hundred miles then we have serious problems.
In my own car, if I find out shearing is a big problem, I will start using 10w30 synthetic in the summer months (I can use 10w30 in warmer months if 5w30 is not available). And I will use 5w30 only in the winter months.
What oils, conventional or synthetic, do not shear badly? If even Schaeffer's oil shears down we have a very serious problem.
Maybe shearing needs to be a serious discussion topic at this board.
In my own car, if I find out shearing is a big problem, I will start using 10w30 synthetic in the summer months (I can use 10w30 in warmer months if 5w30 is not available). And I will use 5w30 only in the winter months.
What oils, conventional or synthetic, do not shear badly? If even Schaeffer's oil shears down we have a very serious problem.
Maybe shearing needs to be a serious discussion topic at this board.
I should mention that I heard a story about the engineers at the auto comapnies when 5w30 oil was starting to be the recommended viscosity for new cars and trucks. The story was that 5w30 was being recommended just so that the auto companies could meet fuel economy goals and that engineers themselves at the auto companies were continuing to use 10w30 in their own personal vehicles.
Synthetics, especially Mobil 1, seem to be resistant to the shearing.
I didn't start this thread because I think it's a major concern that's causing increased wear; to the contrary, wear metals are usually fantastic with 5w30s even if they end up as 5w-20. I just wanted to know if there is a corresponding fall off of HT/HS.
Basically, if someone can show us that 5w30 HT/HS falls off just like the kinematic viscosity, then I'm gonna do a run with 5w-20!!! I just need a little more mental support, that's all
I wanna do it soooo bad but I'm still afraid
I didn't start this thread because I think it's a major concern that's causing increased wear; to the contrary, wear metals are usually fantastic with 5w30s even if they end up as 5w-20. I just wanted to know if there is a corresponding fall off of HT/HS.
Basically, if someone can show us that 5w30 HT/HS falls off just like the kinematic viscosity, then I'm gonna do a run with 5w-20!!! I just need a little more mental support, that's all
Oil loses total viscosity for many reasons. The physical destruction of polymer viscosity improvers, (what is sometimes refered to as shearing but I'll reserve the language debate to another time) and fuel dilution being the primary causes. HTHS is a function of Viscosity so of course, as the viscosity at 100°c decreases so will the HTHS @ 150°c .
It is rare to see where this loss of visocity has caused any problems in Energy conserving oils are recomended.
Does this loss of viscosity
It is rare to see where this loss of visocity has caused any problems in Energy conserving oils are recomended.
Does this loss of viscosity
I got the same story from Lube Oil Engineers (Sun, Exxon, et al) at about the same time: circa 1993-1995.
For a car in a mild climate, such as coastal southern California, 10w30 might be a better high-temperature choice than 5w30, although I do like 5w30 for cold start wear.
I've done a couple of used oil analysis with Maxlife 5w30 synthetic and haven't noticed any shearing:
2003 G35 w/2800 mile OCI measured 60.3 SUS@210F
2000 Toyota Tundra V-8 w/5080 mile OCI measured 63.9 SUS@210F
Maybe you should try a different brand of motor oil if you are concerned about shearing. Good luck.
2003 G35 w/2800 mile OCI measured 60.3 SUS@210F
2000 Toyota Tundra V-8 w/5080 mile OCI measured 63.9 SUS@210F
Maybe you should try a different brand of motor oil if you are concerned about shearing. Good luck.
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