Hey folks, Cooley here.
Got another one of your emails about high tech cars and modern driving.
This one comes in from Ash in Toronto, Ontario, with a question I've had before.
So let's get to it.
He asked, isn't over filling an engine with oil worse than slightly under filling it?
I went with a friend to pick up his first car at a Hyundai dealership, and found out the oil level was overfilled, about a half a quart.
The manager calmly and diplomatically explained, it's not a problem.
And that their mechanics add oil from a pre-measured container that ends up about .4 quarts extra.
Am I missing something, or have modern cars changed the way they deal with overfilled sumps?
PS she says, I'm a DIY enthusiast, I gathered that.
And I've managed to keep my 01 BMW 530 running past 357,000 kilometers.
That's like 220,000 miles and I call that pretty good, especially since you live where there's real winter.
She says I must be doing something write.
Indeed you must.
As to this idea of over-filling oil this the one that gets talked about a little less than under-filling, for good reason, but it's another issue, especially if you're a younger, newer DIY person who hasn't done a lot of oil changes, and all of a sudden, you put in too much.
Is that bad?
Is there too much of a good thing, and if so, what do I do about it?
These kind of questions Come up from time to time.
And I think we should explain it by first understanding why an over fill is even a flank.
Let's look at one of the engines to figure that out.
Okay, let's get our bearing.
So here's a Ford Inline 4 ecoboost motor.
The top part of any engine like this is the head, the valves live in there and the intake of air and the fuel comes into those valves up here.
The middle section is your block on almost every engine.
This is where the heavy iron lives.
You gotta crank shaft, connecting rods and pistons.
All this stuff here either rotates or reciprocates.
And then at the bottom you got your oil pan.
Now we're talking about how much oil you put in here.
When you pour oil in, this is where it goes unless it's momentarily being sucked up by the oil pump, Pushed up through passages in the engine, lubricating parts and then dripping back down here by gravity.
That's how engine lubrication works in most cars.
If you overfill this pan, the main issue is that these rotating parts down here, the lobes of the crank shaft, may start to contact the oil cuz it sits up too high.
It's like beating cream into whipped cream.
It starts to aerate and get foamy as opposed to liquidy, and it's not gonna flow if you do that.
That creates starvation of oil up here where it wants to be pumped to do its job.
And that's the big problem with overfilling.
Not that you so much have too much oil, but that you have oil in the wrong condition because you have too much oil, and it's literally a physical interference problem.
If you find you're well above the range marked off on the car's dipstick, then just drain a little out and recheck it.
It's a little messy, but it's not complicated.
Or if you wanna get fancy, you can buy a Oil evacuation pump that slides down in the dipstick tube.
Now you're particular example [INAUDIBLE], you're friends Hyundai that you bought from a dealer, that last part is key.
Hyundai dealers and their factory have zero incentive to destroy cars they're selling you.
They'd be on the hook for an expensive repair because, Hyundai Has the longest power train warranty in the entire business.
And I'm assuming this is a CPO car, so it would still be under factory warranty.
And that warranty, anyway, is transferable from the first owner.
So no matter what, this is gonna be Hyundai's problem They don't want to mess up engines that they're selling you.
So that's double insurance that I think you're fine with a .4 or so quart overfill.