CJ4 or CK4 Delvac 1300? Which one is the upgrade?

[Best F100]

Couple of quick questions for everyone. Like many of you, I have been using 15W40 motor oils in my gasoline small engines.

Recently, in my local Walmart, I noticed both Delvac 1300 in CJ4, as well as CK4 versions, on the shelf. Both at a rollback price of under $11 per gallon jug. Upon looking up the specs, I noticed that the CJ version has the higher flashpoint (236C) and the higher HTHS 4.3. The newer CK4 version has a flashpoint of 225C and HTHS of 4.1.

With that in mind,

1) Is the CJ4 version the one I want?

2) How can the older CJ4 version have a higher flashpoint, is it really a synthetic blend?

3) Would a Mobil 1 10W30 outperform both of these under 90 - 100F conditions?

I have a Cub Cadet with a FR651V engine (21 HP). Also have a Honda EU6500is inverter generator that has been on a diet of 15W40. Both call for a 10W30, but so far, I can't see any drawbacks in using 15W40.

 

[NH73]

Doesn't matter.

 

[jongies3]

People get in way over their heads about this stuff. CK4 supersedes CJ4 and all previous categories and either will work fine, those engines aren't particularly picky. Although, I prefer to run monogrades in my mowers and log splitter because of the minimal airflow, high revving, and no chance of shear.

 

[AirgunSavant]

I have about 20 hrs on the new Delvac CK4- Amazon had the same deal.
They sold it as CJ4 but CK4 came to me. In a Exmark 708 cc it runs great.
I was surprised that the manual suggests up to 100 hr oil changes and the Amsoil Signature 10w30 I used prior looked like water in less than 25 hours. So I'm sticking with 15w40 from here on out.

 

[beanoil]

Doesn't matter in your OPE, (unless it has a Ford valvetrain).

 

[4WD]

I grabbed a few jugs on sale before the change - but both are plenty stout for your application ...