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SAE 30 vs 15w40

Posted By: dlundblad

SAE 30 vs 15w40 - 10/09/18 09:48 AM

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. cheers
Posted By: Ducked

Re: SAE 30 vs 15w40 - 10/09/18 10:12 AM

No shear
No VII degradation products
No doubt about what the manufacturer recommended
No brainer
Posted By: ofelas

Re: SAE 30 vs 15w40 - 10/09/18 11:41 AM

Amsoil ACD in my 22hp Kohler.
Posted By: zrxkawboy

Re: SAE 30 vs 15w40 - 10/09/18 11:48 AM

Originally Posted by Ducked
No shear
No VII degradation products
No doubt about what the manufacturer recommended
No brainer


Agreed - SAE30 for sure
Posted By: BigD1

Re: SAE 30 vs 15w40 - 10/09/18 12:34 PM

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.
Posted By: Snagglefoot

Re: SAE 30 vs 15w40 - 10/09/18 01:04 PM

A 10w30 diesel motor oil would be my choice. It would be at 10w for the first 5 minutes only. Or, use 15w40 if thick makes you feel better.
Posted By: edwardh1

Re: SAE 30 vs 15w40 - 10/09/18 01:16 PM

30 for me, it works.briggs warns that the multigrades will burn off (my words)
Posted By: Eddie

Re: SAE 30 vs 15w40 - 10/09/18 01:30 PM

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
Posted By: dlundblad

Re: SAE 30 vs 15w40 - 10/09/18 03:03 PM

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.
Posted By: 440Magnum

Re: SAE 30 vs 15w40 - 10/09/18 03:30 PM

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.
Posted By: racin4ds

Re: SAE 30 vs 15w40 - 10/09/18 04:44 PM

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.
Posted By: Propflux01

Re: SAE 30 vs 15w40 - 10/09/18 04:57 PM

Rotella 15w-40 if you can’t find a 30w you want to use.
Posted By: Blaze

Re: SAE 30 vs 15w40 - 10/09/18 05:14 PM

Delo 400 30 wt.
Posted By: beanoil

Re: SAE 30 vs 15w40 - 10/09/18 08:40 PM

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.
Posted By: Warstud

Re: SAE 30 vs 15w40 - 10/10/18 02:27 AM

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
Posted By: Garak

Re: SAE 30 vs 15w40 - 10/10/18 02:49 AM

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....
Posted By: 53' Stude

Re: SAE 30 vs 15w40 - 10/11/18 12:50 PM

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
Posted By: JTK

Re: SAE 30 vs 15w40 - 10/11/18 08:55 PM

SAE 30 doesn't shear?

Pretty sure a UOA would differ.
Posted By: kschachn

Re: SAE 30 vs 15w40 - 10/11/18 09:24 PM

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.
Posted By: Gilitar

Re: SAE 30 vs 15w40 - 10/12/18 02:47 PM

Mobil 1 15w50 in all my air cooled OPE.
Posted By: jeepman3071

Re: SAE 30 vs 15w40 - 10/12/18 02:55 PM

Been using 15w40 for years now on both my own and customer machines with excellent results. Rotella, SuperTech, and Napa 15w40 have all worked well. The only exceptions are snowblowers which I use 0w30 or 5w30 in and generators which I use 5w40 in for easier starting in winter.
Posted By: dlundblad

Re: SAE 30 vs 15w40 - 10/13/18 11:19 AM

We went to Rural King yesterday for the first time in 3 years as it's somewhat out of the way for us. I had forgotten how fun of a store it was. Baby chickens all the way to firearms.

I had to check out the oil section and saw they had various SAE 30's. When the time comes, I'll scoop some up. I'll most likely just use Rotella.
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