I did an oil change. Thought the car took 4.4 quarts but it only takes 3.7 quarts. I poured in slightly under 4 quarts. The engine is a 1.5 in-line turbo (Honda Civic Si). It’s reading past the fill line slightly. How bad is it? Do I need to pour some out? What am I risking? What symptoms should I be looking for?
Automechanic for 10 years here.
No. A little over the max fill line on the dipstick isnt going to hurt it. 1/8 of an inch overfilled or less is okay.
Usually if you don’t prefill the oil filter and only add what they say then sometimes it can be a little under. Its not a big deal.
Way too much and you risk damaging piston rings or flooding, but you really have to fill it to the point its spilling from the dipstick tube.
My wife was a mechanic (lube tech) for a year or two when we were first dating. One guy came in after TOPPING OFF his oil with WATER and was complaining that it wasn’t running right
Its pretty unusual to have lube techs doing any diagnosis, but did she ask him if he likes chocolate milkshakes? Because That’s exactly what you create when you mix water in engine oil. Just don’t drink it.
Having once upon a time overfilled my oil by almost a quart, I think you are mostly right.
Engine oil should stay in the crankcase. During normal operation, some of it is pumped elsewhere to lubricate the crankshaft, cams, and other mechanical components. The rest of the oil sloshes and splashes around the crankcase keeping everything slippery. If there is too much excess in the crankcase, components moving can push the oil somewhere it shouldn’t be.
In my case, when turning left, the excess oil was pushed passed the piston rings and burned in a huge cloud of blue smoke. It wasn’t a proud moment, but stopping in a random service station and having Bruce try to drain a quart of oil out of the engine, because I couldn’t afford a full oil change was awkward.
… Anyway: all of that to say this:
If you have too little, your oil pressure light will probably come on. If you have too much, you’ll notice it somewhere else.
If you find yourself overfilling often, or if you are in the business and do heavy line work like I did (engine/transmission replacements and overhauls), just save yourself the time and get a fluid evacuator. If you overfill something you can pump a bit back out, they make them with pneumatic attachments or with a handpump that looks a bit like a bicycle tire air pump. Shove the little feed tube down the dipstick and pump whatever you need to back out.
EDIT: Fluid Evacuator
we’re supposed to pour it onto the oil filter too?
I mean, you don’t HAVE to. But you can pour some oil into the filter to pre-fill it so the oil doesn’t have to pump so long for the air you cycle out of the system, but the amount of time that happens for is so small it basically doesn’t matter. If the oil filter is easy to access and faces upward (the solid part faces the floor and open part faces up) then I would do it, but I wouldn’t do it in any other circumstance just to not have oil spilling and making a mess everywhere.
Youre not going to blow up the engine if you don’t. But it gives some people better peace of mind.
I think it’s easier to fill a little extra after having turned on the engine.
I just don’t pil change, it might show a little high, then you run the motor to cycle it through the system then it levels out. Good enough. A little less or extra doesn’t hurt anything.
Source: not a mechanic, but I know a lot of them and I’ve never taken my personal vehicle in for a change in 25 years.