Lip on Oil Pan - Purpose?

I have a 2005 Camry. Both the oil pan for the engine and transmission have a lip around the perimeter of the pan. What function does this lip serve and what is its purpose? Seems like it’s only purpose is to make people’s life harder in order to prevent you from using an open end or box end wrench. I was thinking it was to prevent rocks from hitting the bolts holding the pan to the engine or transmission, but I’m not sure this is it’s purpose.

It stiffens the flange of the oil pan.



Thanks for the help. What exactly do you mean by this “stiffen the flange”? Sorry if this is a dumb question. It stiffens it, so less likely to move or shift around?

If that lip wasn’t there, and you tightened the oil pan bolts, the flange would be tightened only at each bolt against the engine.

And not between the bolts.



Do you have a metal ruler in your house? If so, you’ll note that you can bend it without too much effort. Now picture welding a second ruler in a perpendicular fashion so that the cross-section is a “T”. You’ll no longer be able to bend the first ruler even with great force, so it will always be perfectly flat.

Weld the second ruler at the edge of the first ruler instead of the middle and you’ll basically have the lip you’re describing.


In a related way, that’s why flat panels have a raised area embossed in them. That makes the panel a bit 3 dimensional, less flexible (stiffer), and reduces that panel’s tendency to vibrate.

Open end wrench ? Seems like most people would use a ratchet and socket .


It is like metal siding being ribbed. This acts to stiffen a very light material.

I would never try to remove an oil pan from an engine. I take enough lip from Mrs. Triedaq without having to.put up with lip from an oil pan


they have to, since they can’t use a wrench because of the lip…


If Mrs Triedag reads this I am sure you will be getting more than lip also telll the dog to move over as you will be moving in the dog house. :smiley: :laughing:

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I don’t know that I fully understand. I’m just trying to learn here. Please bare with me. Sorry if this is a stupid question.

For my vehicle, the heads of the bolts and their washers do NOT come into contact with the lip. Here’s an example photo from a YouTube video.

So wouldn’t the clamping force generated by tightening the bolts down only act at each bolt location because they don’t come into contact with the lip?
I would understand that if while tightening the bolts down, part of the head of the bolt or washer came into contact with the lip, that a clamping force would also be applied between each bolt via the lip.

Once again, sorry if this is a stupid question. I’m just trying to learn here.

Of course they don’t . As your were told the lip is to give strength to the pan . The bolts and washer need to set against a flat surface to hold and remain in place . If they were to contact the lip they might crush the lip or not really provide proper pressure . It should not be that hard to understand. Me thinks you just go looking for problems.

@YoshiMoshi3 What are these 2 degrees you have and did you enroll in that automotive class you asked about ? Asking for a friend .


The bolts aren’t supposed to contact the lip. That would crush the lip, defeating its purpose. The lip provides rigidity to the edge of the pan

This is a family-friendly site. Please keep your clothes on. We can’t bear such behavior!

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The lip is formed into the stamped steel part so the part seals against the component it’s trying to seal.

The hardware used to provide the clamping force doesn’t come in contact with the lip, but prevents the stamped steel part from deforming when the hardware is tightened.


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Many folks don’t understand mechanical concepts. It’s life. A piece of paper flutters in the wind. Fold it in 1/2. Like a vee. It will have more stiffness. Get it? Go crazy. Fold a paper airplane. Try and bend it. It now has stiffness. A flat piece of paper now has rigidity just by folding it.


It was good to see that you received a number of informative replies.
It’s also common to ignore the replies that don’t add any value.

Also, all the bolts around the pan create an equal pressure on the gasket making a seal. if you only had 2 bolts on the pan it would leak. and you should not make the bolts super tight. so tight that it squeezes the gasket out.

Thanks guys. I understand better now that it is there not to apply clamping force between bolts, but to add to the strength of the material itself.

I’m not sure that it matters, but I got a bachelors and masters in Electrical Engineering. Almost done with a graduate certificate in Systems Engineering. The automotive program is great! Really glad I’m doing it. It’s at an affordable community college, and there’s night classes. You get an associates degree out of it as well. Apparently one of the goals of the program is to teach you everything you need to know to pass the ASE test for master technician. So far I have taken the engine class and welding class. The engine class was great, completely took apart an engine from a CR-V. The welding class was also lots of fun. I’m really glad I didn’t do Lincoln Tech route, it costs way to much. But unfortunately, they seem to be the only school that will teach autobody repair.