oil in transmission

Did a dumb mistake this morning.

Mixed up the 10w-40 bottle with the transmission fluid bottle and accidently poured motor oil into my Avalon's transmission.

Put about half a cup in (a cup at the very, very most) before realizing that the fluid was brown, not red.

How bad is this? Must I have the fluid replaced? And if so will it be sufficient to just drop the pan and replace the gasket? Wasn't sure if this replaces all of the fluid. Haven't done this before but doesn't seem too hard.

Thanks, Brian

Reply to
denaman
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Do *NOT* start the car, drop the transmission pan, and drain all that you can. You do NOT want the oil going through your transmission. Put it back together with a new filter and fill and you should be OK.

If you have run the car, then you'll need at minimum a good transmission flush.

Definately do NOT run/drive/start the car.

Reply to
Noozer

That's dumber than dumb.

Do NOT start the vehicle. Drain IMMEDIATELY. ATF is mineral based, while motor oil is paraffin or asphaltum based. Combination of the two will cause carbonation in short order. Not only that, non-mineral oil will destroy the clutches and seals in the transmission.

The last automatic transmission that specified "motor oil" (20W-20 MS grade) were the GM truck HydraMatics, which ceased production in

1962.
Reply to
DeserTBoB

Bob, While your recommendation to drain the oil and ATF is proper, your chemistry is not exactly spot on. Mineral oils ARE petroleum based, just as paraffin oils are. Same family.

Reply to
<HLS

Yup, damn near every lubricating fluid in cars is mineral based. Of course, it's a broad term. It does however rule out DOT5 brake fluid if that helps any...

I would drain the trans at the plug in the pan and refill several times. Use Dextron III on 1995 to 2004, and Type WS on 2005-up Avalons. The OP will have no worries if he does this.

Toyota MDT in MO

Reply to
Comboverfish

Is it necessary to drop the pan? Because I thought that Toyota transmissions had drain plugs.

Reply to
larry moe 'n curly

Actually you're right, the Avalon does, in fact, have a drain plug.

Reply to
denaman

Reply to
Shep

It probably holds at least a gallon (16 cups) of transmission fluid. A half a cup is basically nothing I would worry about. It's only 3% of the total.

Reply to
Ashton Crusher

Was able to drain the old stuff before I twisted the key. Am back to normal again.

Thanks everyone for the replies.

Reply to
denaman

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