Oil viscosity question

[Chris142]

Say someone has 4 qts of sae40 oil and they add 1 bottle of the stp in the blue bottle. What would the viscosity be? Sae45,50... thicker?

Asking for a friend

 

[KCJeep]

A bottle of STP will generally jump you up one grade with the common thinner oils, on something already so thick as SAE 40 not sure. Thicker though.

But you could thin it back down with MMO.

 

[Chris142]

A bottle of STP will generally jump you up one grade with the common thinner oils, on something already so thick as SAE 40 not sure. Thicker though.

But you could thin it back down with MMO.

Naw I need it thick. It's my old tractor. It's getting sae 50 next time.

 

[Rand]

Naw I need it thick. It's my old tractor. It's getting sae 50 next time.

it depends on what you add it to.

if you add STP to a thin oil it will have a bigger impact vs adding to a 40-50wt thick oil.. as the viscosity difference between the 2 is greater when adding it to thinner oil.

 

[JavierH19]

You can use this calc to find the value after finding the kv100 of both to punch in but i wouldn't bother, just use 20w-50 or m1 15w-50.

Mixing viscosities | Widman International SRL

www.widman.biz

 

[addyguy]

Since straight-weights tend to already be at the upper end of the grade, you’d most likely get at least a thick 50-weight oil.
It won’t hurt an old tractor in the Cali desert!