The Case of the Missing Oil Filler Cap

I'm having an unusual issue with my 2023 Tacoma's oil filler cap. For the second time, it's gone missing.

Here's the back story. I bought the truck new in April 2023. I decided to do a 1000 mile oil change and keep the truck on a 5000 mile interval. I'm usually diligent about looking the truck over after a service but after the 1000 mile oil change I didn't. I drove for around 1000 miles before popping the hood to check on things. Imagine how angry and stupid I felt when I noticed the oil filler cap was missing. The engine bay was dry and the oil level was still full. I called the dealer and explained what happened. I brought it by, they replaced the cap and did another oil change. It seemed like some tech had got in a hurry and simply left the cap off. I decided I would go to another dealership in the area to have it serviced in the future.

This past August I took the truck in to have the oil changed at 20k miles. After the service I walked around the truck, popped the hood, and made sure the oil filler cap was on and tight. I had surgery in September and had some complications. I wasn't able to drive for a few weeks so the truck wasn't driven too much. As of today, I put roughly 300 miles on the truck since the service in August. Today while checking tire pressures and the oil level I noticed the oil filler cap was gone again. What the heck? Again, the engine bay was dry and the oil level full.

So at this point I'm really baffled by what's going on. I'm questioning whether the tech made a mistake after the first oil change. I know it wasn't a mistake this time because the cap was there and tight after the 20k mile service. The only thing I can think of is there is some kind of issue with the oil filler neck and the caps are coming loose. It makes me kind of nervous that the internal parts of the engine have been exposed twice now. I have an appointment to drop it off at the dealership tomorrow. I'm interested in seeing what they come up with as an explanation.

Has anyone else encountered an issue like this? Oil filters coming loose seems to be a more common issue but not oil filler caps.

 

I check my oil at least once per month and also check the oil cap which is always on tight. Over the years, I have seen threads about missing oil caps.

https://www.tacomaworld.com/threads/missing-oil-cap-2020.803691/

 

Never heard of it before in my life.
Never talked to anyone that's heard of it.
Never talked to anyone, that talked to someone, that had heard of it from someone else.
Finger tightened by a toddler should more than enough.

 

This just happened to me last night as well (no oil splashed anywhere and oil level totally full). I know it was on at least a few weeks ago when I aired down/up for a trail I did. Went to air up my wife's tires last night (5hr family road trip today and was making certain preps) and noticed it was missing...

Per the other thread, I went and picked up an Autozone one. Going to be keeping a better eye on it moving forward and maybe keeping a spare.

 

I've read the aftermarket caps seem to stay secure better than the OE caps. Keeping a spare around is a good idea.

 

It has happened numerous times.
Most of the the dealership gets the blame. But it’s happened enough, I’m starting to wonder myself if the is some issue somewhere?

Seriously, there has been at least 3 other post about this.

 

Yeah, I can't remember what the OEM one was like as I was never paying attention that closely, but the Duralast one from Autozone actually seems solid for $9.99. Lifetime warranty too!

 

I never use more than two fingers on an oil cap, and without fail, it takes a fist grip to

I've driven off without my gas cap.
What I've never heard of, is one falling off, that was on...

 

drill a hole in it and put a wire on it

 

When I do my oil I finger tighten mine. By the time the next oil change rolls around (i do 3k mile / 5k km intervals) it seems to have tightened itself to the point that it needs a little tug with some channel locks just to pop it loose (opposite problem?).

I'd guess 90% of these occurrences are due to whoever does the oil change but as for the mysterious missing ones.... weird.

 

This. And, it is similar with our two Subarus.


This has been coming up enough though that it has me wondering. The only thing that I can think of is that the seal is falling out. I think beyond the preload that the seal gives, the material itself takes a set and makes it difficult to remove. The seal falling out, or not being there from the start, may explain the issue?

 

Have you checked to see if it is laying in the skid plate?

 

So in past posts, I commented that caps auto-loosening was bunk and blamed the issue on dealer service. When this happened to my son I told him that this was why he had to do his own oil changes. Well, last week I had the hood open on my '23 and checked the cap and it was indeed loose and I know I had tightened it during the last change that I did. When I checked it again today it was still tight, but I gave it a slight additional turn. This may have been a mistake because the cap clicked as it jumped a thread, loosening up. I pulled it off and looked at the threads - seemed ok so I screwed it back on loosely and it seemed that there was a lot of slop in the thread engagement. It certainly did not feel the way the cap on my '96 Tacoma does, though that cap screws into a metal valve cover.

So I'm left with 3 theories for those who have had a missing cap:
1) Yes the dealer left the cap loose or off.
2) The sloppy thread engagement allowed the cap to vibrate loose
3) The sloppy thread engagement allowed the cap to vibrate tighter to the point that it skipped thread. (Probably not likely)

The other thought in my case is that the original cap on my truck was lost by the previous owner and was replaced with a cheap aftermarket, hence the sloppy thread engagement. I'll have to give it a good look tomorrow.

 

My dealer left my oil cap off... last time
In your case no idea what happened to your cap the second time

 

Only in this thread, it seems to be 22 and 23 models. I'm wondering if the part numbers for either the cap or the filler tube have changed since 17 as I have the exact opposite situation. Manufacturers change over time etc so does engineering / materials used etc. I'm wondering if this is a year specific thing. I'm still sticking to the 1) choice of not changing your own oil and some goof making minimum wage (or slightly higher) just forgot for 95%+ of these occurrences.

 

I did. I crawled around and checked around and it is gone.

Not a bad idea. I thought about just cranking down on it until the plastic filler neck breaks. Top it off with a little red Loctite for good measure.

I dropped it off at the dealership this afternoon. Both the Service Advisor and Service Manager were perplexed. Both agreed they've seen caps left off or not tightened down and come loose, but not something like this. I'm interested to see what they come up with.

 

I've upgraded to a TRD Oil cap and you're right, it does take a fist grip to take it off! lol

But previous cap and current cap have not self-twisted off.

 

They don't come loose. If you leave it on the battery or the engine cover they have a tendency to roll off and get lodged down by the skid plate. Much like a game of Plinko from The Prices Right.

My advice would be to set it somewhere else. Maybe a cup holder near the shifter.