SAE 30 vs 15w40

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I have a 50 year old air cooled Kohler engine that specifically calls for SAE 30.

Of the 2, which modern oils would be better to run in this situation?

I realize SAE 30 is slightly harder to find, but let's take that out of the equation for conversation sake.
cheers3.gif
 
No shear
No VII degradation products
No doubt about what the manufacturer recommended
No brainer
 
Originally Posted by Ducked
No shear
No VII degradation products
No doubt about what the manufacturer recommended
No brainer


Agreed - SAE30 for sure
 
Even on my modern three year old Honda mower engine that calls for 10W-30, SAE 30 works better for me. Honda does say SAE 30 can be used at 50 degrees and above from what I remember. It drinks PYB 10W-30. Briggs SAE 30 no noticeable consumption like night and day difference.
 
There are some low grade 30 weights out in the market that arn't suitable for anything but the oil can. If a 30 is spected for diesel use then OK, otherwise use a stout 10w30 (T5) or a 15w40. JMO. B&S recommends a 5w30 Synthetic for ALL it's engines.Ed
 
Originally Posted by Eddie
There are some low grade 30 weights out in the market that arn't suitable for anything but the oil can. If a 30 is spected for diesel use then OK, otherwise use a stout 10w30 (T5) or a 15w40. JMO. B&S recommends a 5w30 Synthetic for ALL it's engines.Ed



You make a good point about low grade 30's.

I'd use PYB, NAPA or Rotella.
 
Since I have the exact same situation, I'll tell you what I've been using for the past 10 years: Rotella T6 5w40. Old air-cooled engines aren't picky about precise viscosity quite so much as they are about temperature tolerance, viscosity stability, and resistance to sludge formation, detergency, etc. since the sump runs un-filtered.

My big problem with current SAE 30s is that they're only available two ways: 1) low-end oil that I wouldn't put in my worst enemy's lawnmower, let alone my own... 2) high-end boutique racing oils. T6 is a commodity oil that fits the bill perfectly, and has worked in my air-cooled engines for a lot of hours now.
 
Originally Posted by 440Magnum
Since I have the exact same situation, I'll tell you what I've been using for the past 10 years: Rotella T6 5w40. Old air-cooled engines aren't picky about precise viscosity quite so much as they are about temperature tolerance, viscosity stability, and resistance to sludge formation, detergency, etc. since the sump runs un-filtered.

My big problem with current SAE 30s is that they're only available two ways: 1) low-end oil that I wouldn't put in my worst enemy's lawnmower, let alone my own... 2) high-end boutique racing oils. T6 is a commodity oil that fits the bill perfectly, and has worked in my air-cooled engines for a lot of hours now.


Except T6 5W40 is NOT a SAE30WT and is not the oil it used to be either... they have stripped a lot of the good stuff from it over the years to meet the dumb EPA/insert BS org.

Shell/Rotella still makes a good SAE30 and Amsoil has some great offerings as well.
 
SAE 30, there really is no alternative. As stated, no VI to shear, extremely heat tolerant. I disagree about only 2 types, cheap and boutique. SAE 30 is available lots of places, TSC has their house brand, Rotella 30 weight is available almost everywhere oil is sold including WM, and they have their house brand SuperTech fleet as well. Mobil 1630 at Rural King, LubeKing is at Farm and Home. I'm running Mobil 1630 in all my OPE now.
 
Last edited:
Originally Posted by dlundblad
I realize SAE 30 is slightly harder to find


Walmart has Rotella T1...Rural King has 3 different brands of SAE30
 
Originally Posted by racin4ds
Except T6 5W40 is NOT a SAE30WT and is not the oil it used to be either... they have stripped a lot of the good stuff from it over the years to meet the dumb EPA/insert BS org.

Which can equally apply to API monogrades you see on the market....
 
Originally Posted by Warstud
Originally Posted by dlundblad
I realize SAE 30 is slightly harder to find


Walmart has Rotella T1...Rural King has 3 different brands of SAE30


Yep, Harvest King, Rotella and Mobil
 
Originally Posted by JTK
SAE 30 doesn't shear?

Pretty sure a UOA would differ.

I'm not sure how it could with such relatively short hydrocarbon chains. The VII molecules are huge in comparison and far more prone to cleaving from mechanical force.
Nearly every UOA on here cannot distinguish between fuel dilution and actual shear so that is what I think we see most of the time.
 
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