Oil change with mixed viscosity

[1runner]

I have an 04 4Runner, today when I changed oil, by mistake I put one qt of 10W-30 with 4.5 qt of 5W-30, same brand. Should I worry about it?

The Owner's manual says it is OK occasionally use 10W-30 though feul economy may suffer. It said nothing about mixed viscosity in the same crank case.

 

[greasefingers]

It

 

[jeober]

Consider that you now have 6W-30 oil
Certainly a good blend.

I'm surprised at the owner's manual mention of fuel economy - the cold viscosity rating of an oil is at 0^C and important for cold start up consideration. At engine operating temp. (100^C) 5W-30 and 10W-30 oils have similar viscosities.

 

[1runner]

THANKS!

The Owner Manual says: 5W30 is for "good fuel economy and good starting in cold weather" and suppose to switch back to 5W30 "at next oil change" after 10W30. I figured with 10W30 it would be bad for cold starting like you said and for fuel economy...

BTW, I did a bit more searching, 10W30 is good for 0^F (-18^C) so it is thicker but not so thick to be a goo at "normal" cold temperature

 

[jeober]

Actually a 10w-30 oil has fewer viscosity improvers (polymer additives) than the same type 5w-30. So less additive means more lubricating molecules per volume.

I switch between 5w-30 and 10w-30 depending on the seasons. Probably overkill but since I change oil often it's easy and free to do. I change oil about 8 times per year.

 

[greasefingers]

Yea it would be a completely different story if he actually used 10w-30 and lived in a very cold climate, but he has only added one quart of this.

I have changed my motor 17 times so far (using 4,000 mile intervals)