I have a 2001 Toyota Highlander with the V6 engine. I went on a road trip recently, replacing the oil just before the trip. On the way back, I noticed RPM spikes while driving up a steep mountain grade of 5%. I finally arrived in Florida and all seemed well. Keep in mind that I regularly keep up with all maintenance/oil checks. My car currently has around 125,000 miles on the odometer. The day after the road trip, I fired up my car and got more viscous RPM spikes, jerking, vibration, and clunking noises. I looked down at my panel and just then, the 'check engine oil' light came on. I turned the vehicle off, popped the hood, and checked the oil. There was no oil in my car. I remembered during the road trip, on the freeway, someone in front of me lost their load of wooden furniture. Swerving to avoid the major pieces of wood and debris, I straddled a small wooden arm. A **** stick, if you will. I heard it clink under my car. The next oasis, I inspected for damage, found none. It was a **** stick. Remembering this, I checked under the car for any oil leaks... there were none. ((If there is an under-the-car oil leak, during driving at freeway speeds, the oil would have fanned out and dirtied up the undercarriage.)) It was completely clean. I put 5 quarts of oil in my car and started her back up again. She seemed fine for the day.

The next morning, I had to get to my class. I got in the car, and drove off. While driving up an incline to get onto a freeway entrance, my car's RPM's spiked again, she made a few more noises that progressively got louder. The 'Vehicle Service Check' and the 'Check Engine' light came on. I slowed down, turned on my hazards and pulled over. I checked the oil level once more. It was perfect. I had it towed immediately to a mechanic.

My theories so far:
1.) Loss of oil due to some slow leak.
2.) The oil change place somehow didn't put enough oil in my car... which led to engine failure during the road trip.

He opened the engine up and found the problem: A broken connector rod. When the connector rod broke, it shaved a nice crevice in my cylinder wall as well. I asked him if it could have been because of any lack of oil ((No thermal dissipation would cause those connector rods and other components to turn red hot and snap)). He then led me to the cam where I answered my own question:

There was no evidence at all that there was no oil at any time during my engine's life. Oil flows down. The cam is on top of the engine, so the first place where parts would have started grinding would be the cam. The cam looks perfect, almost pass off as brand new. I then asked him if it could have been from an accidental over-rev. Nope... Over-revving would have caused the valves to bend due to the piston hitting them at such high RPM's. It was a complete mystery. He has no idea what could have caused it.

I'm now looking for any kind of reasoning or explanation as to what could have happened. I'm looking for anything that I can use to have the insurance company handle this. I'm speculating it might have been a structural defect. ((Pre-use hairline stress fracture or an microscopic oxygen bubble getting trapped during the casting process))

Here's the strange part: If the oil from the first part of my story didn't go down, or up... where the hell did it go? I don't think I burned it ((I would have smelled the oil burning and seen the blue smoke)). AND, if I did burn it, the piston rings would have been worn... they're in great condition. Any theories/ideas?
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Very strange.
I don't go to any of the quick lube oil shops. All are well known for screwups like not putting in the correct amount of oil, or not putting in any at all. On a friends truck, they "forgot" to reinstall the air filter. He didn't notice until many dirt road miles later.

It could be from lack of oil. How is the other side of the piston rod where it connects to the crank? True oil falls down, but it's also pumped into the crank and maybe that ran out of oil first.

My guess is that the piston rod was weak from the factory, and when it started to loose oil pressure and things got hot, it was the first thing to break.

It seems just fine as well.

Exactly what I thought. But if I go that route... the insurance company will wipe their hands clean. And since it's out of warranty, I'd have to pay for any repairs. :( I wrote a letter to Toyota. If I'm lucky at all, they might find my case, 'interesting' and lead some kind of investigation. Well, thanks for the input.

What's your take on the mysteriously disappearing oil?

Hello,

The exact same thing happened to my 2002 Highlander V6 Limited!! I am now in a position where I have to replace my engine for about $7,800 because my connecting rods blew threw the engine.

I have been doing a lot of searching to see if there was some type of recall or anything. That is how I came across your situation. Have you had any luck finding a reason for this? Any help would be appreciated=)

I say it was oil related.... period. Remember heat is highest at the pistons/cylinders. The heads are second.

The connecting rod failed due to lack of oil .