Mixing your (car's) drinks

[Blue_Thunder]

Is there any rule of thumb around which weight you use when topping up your oil?

So long as you are running fully synthetic, would it cause problems say if you had 10W60 at the oil change, but topped it up with 10W40?

I know ideally you would probably want to use the same, but would it cause any issues mixing different weights?

[CliveH]

I'm no expert Scott, but I would think that mixing the relative viscosities ("weights") of oils would simply result in a new average viscosity?

If they are of the same quality and fully synthetic, and providing the mixed oil (eg 10W50?) meets your requirements, then I wouldn't envisage any issues.

I'm sure it's not as simple as that, and no doubt Oilman will be along to put me right soon...

[Blue_Thunder]

That's what I thought. I was just worried incase the oil settled and seperated if the car has been standing for a while and perhaps caused pressure fluctuations when it's up and running. Guess it probably gets pretty well mixed up inside the churning engine.

You'd think I have enough to worry about without stressing over this as well!