oil change!

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.

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.

Absolutely nothing to worry about.

whoops...so I picked up castrol 10w30 today...except that the three quarts behind the first one at the store were 20w50....and i only noticed after i changed the oil

how bad will it be if I run my car now? Even to drive to the auto parts store and get the better stuff? Is it undriveable with 1qt 10w30 and 3qts

-sachin

Actually...with one quart of SAE10 and three quarts of SAE20, wouldn't I have 17.5w oil in there?

Wrong. More like a 17.5W45.

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.

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:

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.

Wrong. More like a 17.5W45.

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.

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:

It was obvious what you had done and that is why I included the smiley at the end. I was having some fun with you.

I never said it did.

I don't think this is correct. Every source I found, including the one listed below written by an engineer at Texaco says otherwise.

I believe my facts are straight, and I provided a credible source to support what I said. Can you provide a source to support your assertion that a 10W30 oil performs the same as a 10 weight oil at high temperature rather than like a 30 weight oil which is what I believe is true and what every source I've read says is true?

I never said I've never made a mistake, I simply pointed out several mistakes in your first post. Unfortunately, it appears you still are making at least one mistake persistently. No offense, but I trust the engineers at oil companies more than I trust someone on a newsgroup when it comes to the topic of oil.

Matt

I think you meant to say "Heat up 10W30 to 200 degrees and heat up 30W to 200 degrees and run them through a Saybolt Universal orifice and they will flow exactly the same. This is because (at that temperature) they are both SAE30 viscosity!".

Bill Putney (to reply by e-mail, replace the last letter of the alphabet in my address with "x")

Unfortunately, Bill, I think he really meant what he wrote.

Matt

These websites will give you most of what you ever need to know about motor oil

Yes, a nice overall summary, but sounds a little like an Amsoil commercial at the end with the 25,000 mile oil change comment/link.

Matt

I had a better site than those but can't find it.. while none of them can be seen as definitive, they do show that no matter who you ask, you will always get a slightly different answer.. it does really come down to driving conditions and style, and in that respect we are all different.. in this part of Canada (eastern Ontario) the wildly varying temperature change from high summer to 'damn cold' winter makes people change oil regularly regardless of what others might tell them..

We have a similar problem in northern PA, which is why I use Mobil 1

Matt

lol.. -30F up here is considered a heat wave at times.. have seen the thermometer drop to -45.. fortunately, it does not happen too often, apart from this year.. :)

We only hit -30F about once a decade or so, but I like my car to start and lubricate well even on those rare occasions. Our coldest this year was -20. Even at -45F, synthetic is a lot better than dino oil, although probably still too viscous without a block heater.

Matt

The previous owner of my Jeep failed to take the option of a block heater, and I have been feeling cheap for a while now.. but I do have a block heater ready to be fitted,, it is a cute little thing too.. seems a shame to spoil it by fitting into the block.. I have a Jeep 'Thermoguard' battery wrap too.. still in its box as it is way to cold to go out and fit it.. needless to say, the Jeep has started up every morning anyway.. the thermometer reads

Depends how cold it is. At -30 it won't start. At 50F no problem at all.