Hold on a minute. re: my math error - I misread it as 3 of 10W and 1 of 20W
so an honest mistake and you are correct.
BUT the first number is the oils SAE viscosity as indicated in a standard
Saybolt Universal viscosity test. The flow time is converted to the SAE
number.
The second number does NOT mean the stuff turns into 30 or 50 W when hot.
This is chemically impossible at the temps engine oil runs at. What it DOES
indicate is that it acts similar to 30 or 50W at a specified temp due to the
additive package. Meaning it has breakdown and load bearing properties of
the larger number. Heat up 10W30 to 200 degrees and heat up 10W to 200
degrees and run them through a Saybolt Universal orifice and they will flow
exactly the same. This is because they are both SAE10 viscosity!
Before you go blasting someone you ought to really have all the facts
straight. It must be wonderful to have gone through life and never made a
mistake.
--
Mike....................................................
"Opportunities are spawned from crisis"
Rufus said:
Don't even worry about it. All you basically did is raise the base
viscosity a small amount. Mathemattically you now have 12.5W30 in there.
Just put the whole thing out of your head and drive the car until the next
regularly scheduled oil change. Only next time check all the bottles
first.
Wrong. More like a 17.5W45.
A 1990 vehicle most likely has enough miles on it to have worn the bearing
clearances a little so the microscopically thicker oil might even be a plus.
The 30 and the 50 part of the oil rating has nothing to do with the actual
viscosity.
Wrong again. The first number describes the behavior of the oil when
cold and the second number describes the behavior of the oil when hot.
Absolutely nothing to worry about.
I agree that I wouldn't worry too much about it as it likely won't cause
any trouble other than slower cranking when starting and a probably
imperceptible loss in mileage. I would worry though about the answers
Rufus gave.
If you want correct information, here's one place to check out:
http://www.texacoxpresslube.com/carcare/article_viscosity.html
Matt