Did the mechanic ruin my car with double dose of oil?

Question

I brought my new car in for its 3rd oil change. When I was driving back to work the car started sputtering and billowing black smoke out the tail pipes. I brought it back to the dealer and they told me the mechanic accidentally put the oil in twice. I had driven it for about 25 minutes in this condition (to work then turn around go back). They sent me home in one of their cars so my car could sit and drain for the night. The next day they brought my car to me. No smoke, no stuttering.

Its been about 2 months. In the first month as I was stopped behind a car who was turning the engine made a loud growl sound for about 10 seconds. Never happened again.

Now this week the car has started sputtering slightly when I'm idling in park or drive.

Did they wreck my new car??

Answer 1

If it's a new car, the engine should never be making a "loud growl sound" and should never sputter at idle. You should take it back in if no other reason, because of that whether it's related to the oil being overfilled or not.

First, several things can happen in an overfilled oil scenario:

1. Your crank is whipping the oil up so that it becomes mostly air, causing improper lubrication of the engine components and potential damage to the oil pump. Yours was definitely overfilled to the point this was happening! But, that doesn't necessarily mean the pump or other components were damaged.
2. When the engine is grossly over-filled (like it was in your case), it can make it to the exhaust track and it will wreak havoc on your catalytic coverts and potentially cause issues to censors in your exhaust system. This often shows up on a scan, assuming they did one -- which is unlikely according to my personal experience with this stuff.
3. If it gets into the combustion chamber, passed the oil rings it can cause plugs to fowl - you were definitely burning the oil as evidenced by the black smoke.

Of course, none of this is good for your engine. But, you did not drive very far or very fast. That's good as more severe issues like bent rod etc. are unlikely to have occurred -- also this would probably be obvious to you later if it had as you'd be hearing knocking and having rough idle etc. It concerns me that you do have a rough idle.

To say the least, you should take it back and start holding them accountable. Tell them it isn't running right and is making noises on occasion. If it were me, I would demand a complete diagnostic be done including checking the oil pressure at different RPMs, engine timing, and of course running a complete scan for codes. Every time I've heard of this happening, the culprits will try to blow you off and say it doesn't cause damage - that is not always true! Demand they scan it and show you the results. They should not charge you for any of this. But, if you feel as though they are blowing you off -- likely to happen in my experience -- go somewhere else, explain the scenario and pay for the diagnostic work only.

Keep in mind that not all dealerships have very experienced techs. My experience, more often than not is that the dealership is about on par with pep-boys or worse. Don't take their word for anything. The fact that it was overfilled is already proof they are careless amateurs. I would be preparing for a lawsuit.

Answer 2

Regarding the follow-up comment above... any mechanic or service manager who tries to tell you "too much oil can't damage an engine" is trying to pull a fast one. Too high an oil level causes overpressure that can lead to all kinds of havoc such as blown or damaged oil seals just for starters, to say nothing of the other issues mentioned by others like the excessive level meeting the bottom of the crankshaft and so being "whipped up" (or just as likely causing extra drag and friction right where it's never intended to be, and maybe bearing contamination/extra wear), excess flooding of the pump, passing through of oil to the exhaust system (catalysers get very hot, and don't like being contaminated).

There's a reason dipsticks have "maximum" marks on them as well as "minimum"... you don't just put oil in until it reaches the minimum mark, then dump in whatever you happen to have left and hope for the best. "Accidentally" putting in the oil twice should be something you can't miss, if you're actually checking the level during and after filling, to make sure that it's not only over the minimum (you need to make sure of THAT!), but no higher than the maximum.

I don't think I've yet had a vehicle where the manufacturer recommended oil fill volume actually matched how much was needed to reach the maximum mark... it's always been a little less. After seeing it over-fill a bit the first time I did it, running to the recommendation, I've always stopped at least a pint / half litre short, let it settle for a minute (or 2~3 in autumn/early spring, 5 in winter), checked the level, and topped up accordingly (there's usually about that much between the minimum and maximum, so you can make a reasonable guess about how much of the remainder to put in). If what they're doing each time is dumping out the old stuff and then refilling with the exact manual-recommended amount, without accounting for how there will always been quite a bit of the old oil still lurking in different parts of the engine, and NOT checking the dipstick after filling... which is the only way they could possibly have missed a "double" fill... they're likely habitually over-filling every single car that passes through their doors, to a greater or lesser extent.

In short: cowboys. Get whatever reparations you can from them, complain like hell to corporate, and do not, under any circumstances, ever go back there once the situation is straightened out.