Piston Slap: The Low Oil Pressure Safety Net? (Part II)

Sajeev Mehta
by Sajeev Mehta
piston slap the low oil pressure safety net part ii

Emmanuel writes:

I own a 2016 Ford Focus SE. The oil light came on, so I went and put a quart of oil in. Unfortunately, I forgot to put the oil cap back on, and realized it too late — when I came to a complete stop, I noticed oil was on the ground.

Luckily, the cap was still under the hood where I sat it down. So I put the cap back on, but the oil light was still on. I went to get some more oil. On my way to the store, I happened to be going up a small hill. My car sounded like it was straining to go up it. Anyhoo, once up the hill it shut down, so I waited a few seconds and start it up again. It went a few car lengths, then stopped completely. Now it won’t start at all, or turn over either.

My question, really, is what could it be, or did I damage my engine more than I think? I’m sending you this because I read one of the reviews ( the one with the Impala) and it’s a similar problem/question to mine.

Sajeev answers:

It is 100 percent impossible to know if you damaged your engine, but we can all take educated guesses.

If you’re lucky, this is a well maintained Focus (i.e. oil changes on a regular basis), so there’s no sludge that could could block up oil passages and engine wear was normal for a vehicle this age (and mileage). If it’s sludge free, just like the Impala, the engine computer shut everything down so it’d save itself. That’s how the system works, in theory.

If it ran low on oil, has sludge, and you drove it to the point it shut down, the Focus’ motor might be dead. That’s because there’s only so much a computer can do to save a worn-out engine running on low oil pressure.

Too bad that, four years later, I still can’t Google any more information about these low oil pressure safety nets. What say you, Best and Brightest?

[Image: Shutterstock user ninefotostudio]

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.


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  • Pwrwrench Pwrwrench on May 18, 2019

    As others have mentioned vehicles are different; Some have low oil pressure warning light, some have low oil level light, some have both. Some have a system to stop the engine from running with insufficient oil/oil pressure. About oil (710) caps left off/missing; This will also depend on the vehicle and motor. Some motors will puke out enough oil in a few miles of driving to lead to engine damage or a fire if the oil gets on something hot like the exhaust. Others can go a long time with just a small mess resulting. Some will record an error/fault code in the PCM/ECM. Similar to a loose or missing gas cap. The oil cap can be considered part of the PCV system and is part of the emission controls. That is probably why the post about the engine stalling when the cap was removed. Possibly the PCV was malfunctioning or that the way it is. Can't imagine a scenario where the engine designers will want the engine to run without the oil cap. When I was in the vehicle service business I found it difficult to inform vehicle owners of these things, such as checking the oil level with the stick or not running the engine when warning lights are on. Typical response was "I don't have time for that/ I had to get someplace." Often they wanted a "free" or discount repair on a vehicle they bought somewhere else and was 10 or more years old and now needed an engine repair/replacement. I suppose now it's worse as people are used to fixing electronic things with new batteries or software updates. An anecdote: I know of at least several engine types that the oil will run 30-50 Deg F cooler when the level is at the lower mark on the stick. Probably due to the higher oil level getting whipped around inside the engine. This is probably the cause of the earlier post about the 360 that would use the 1st quart rapidly. Saw that on Dodge vans in the 1970s.

  • DenverMike DenverMike on May 19, 2019

    Silly me, I was under the impression cars will tell (with obnoxious flashing lights, buzzers and or chimes) you when you're catastrophically low on oil. I'm sure every car could, but who's asking for that? Everyone is too busy demanding gadgets galore, Apple Carplay and whatnot. It's the same (or similar) when an engine is destroyed from going through 8" of water. Yeah a "low" intake snorkel is for aerodynamic reasons (even on cars with 4 square feet of fake grill), but a bypass flap (or similar) could save the engine, since water does weigh a lot. Being in the auto repair industry, I see both scenarios a lot, and it's as if no one is looking out for consumers. So what's in it for automakers? When it's the owner's fault the engine is destroyed, it's all profits for the OEM amd dealers.

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