PYB 5/10W-30 Pours Better than RT6 at -2F??

[SwampSurvivor]

One of the reasons I use RT6 over Rotella T5 10w-30 semisyn is that I thought it would be "thinner" when it's cold.

I did an unscientific test last night - should have documented it on video.

This is my first winter running RT6 in the Cherokee. The last few winters I have used:
-Formula Shell 5w-20
-M1 5w-30 (from early 90s)
-ST Syn 5w-30
-ST Dino 5w-30 / 5w-20 Mix

Even on the coldest days, it would build oil pressure instantly. I have noticed that the last few super cold starts I have done on RT6, the "CHECK GAUGES" lights stays on and the oil pressure gauge sits at 0. This is a concern for me.

Last night it was -2.

I went out to the car and grabbed the PYB 5w-30, PYB 10w-30 (planning on running a mix in the Cherokee in the spring)and a quart bottle that was a mix of Castrol Edge and M1 0w-20 and the spare jug of RT6 in the back of the Cherokee

The 5w-30 PYB poured significantly better than the RT6 and was definitely less viscous.

The surprising thing ...

The 10w-30 PYB was actually marginally better pouring than the RT6!!

Obviously the 0w-20 mix was the thinnest and easiest.

Strange stuff!

I may buy some new quarts when it gets cold and try this test and document it on video.

Unfortunately, I think this will be the last OCI on Rotella. I decided to do a year run on it because it's a 40 grade for the hot summer days where I'm beating on it in 100 degree heat off road, and I thought the 5w (and synthetic) would make it "thinner". It's too thick for winter use, apparently.

 

[johnnydc]

Maybe try Mobil Delvac to go along with the new beanie hat.

 

[ARCOgraphite]

Another more vigorous test you can do is fill a paint viscometer (funnel with hole) t a specified level, uncover the hole and time how long it takes the oil to drain say 2 oz into a graduated beaker (or shot glass). Then you have some tangible metrics with this "scientfic" method. You can buy a metal funnel and bend the downspout closed to establish a shear point.

 

[volk06]

Thats not wierd at all. The viscosity ranges for 30w and 40w when cold are different. Most PCMO 5w30/10w30 are thinner at lower temps than most 05w-40s. The hths is also higher on 40w oil which makes it thicker at all temperatures. An no, its not too thick at all. There are engines that run this in colder environments than yours all the time. Once you get real cold, -10/-20F, then the difference in base stocks and viscosity becomes real obvious. RT6 actually flows pretty decent at -40F.

Look at the PDSs and check out the 40C and 100C viscositys and you'd be surprised how much higher the RT6 is but it still flows pretty good.