How far can I drive with too much oil?

Question

I have 2005 Nissan Sentra. The car tends to leak oil, so I check it about twice a month. I checked today and the oil was probably an inch above the full line, but I'm not sure why. I got the oil changed in January, and the oil has been fine so far, until now. I haven't added any oil since January and I haven't been driving it very much, maybe five or ten miles a couple of times a week.

I'm not sure what's happening, and I'm not going to just try and drain it because, based on what I read about this, I suspect there's water in the oil. I just want to get it changed, but the place I regularly get it changed at is about 15 miles away. Will my car be okay to drive that far?

Answer 1

EDIT based on comments:

It's a little hard to tell exactly how much oil we're talking about. The dipstick isn't necessarily a linear measurement: being halfway down the stick doesn't necessarily mean that you have exactly 1/2 your normal allotment of oil.

Reminder: as always, this is your car and you have to make the call.

Given that and based on the fact that you have driven the car at all, it doesn't sound like you have a terminally overfilled sump. If you did, the car would likely have broken in a variety of ways (as discussed in a previous question).

It's possible that the car was just sitting long enough that much of the residual oil covering the moving parts eventually dripped back down into the sump. In that case, you'll be fine and the car will appreciate the exercise.

Original:

This might be a simpler issue than you thought: just remove the excess oil. It's not that hard to reduce a slight overfill even if you've never been under the car before:

1. Locate a long piece of thin flexible tubing (e.g., aquarium pump tubing).
2. Remove the dipstick and set aside (you probably already have it out since you just checked the oil).
3. Feed the tubing down the dipstick tube, leaving plenty sticking out so you can keep a grip on it.
4. Place your thumb over the end of the tube and pull it out. The tube should come out full of oil.
5. Stick the end of the tube into one of the many oil cans that you have around since you've been topping off your oil all the time.
6. Wipe down your dipstick and check your oil level. If it's still too high, return to step 3. If it's too low, pour some of the oil back in and recheck.

If you have a fluid extractor, you can actually remove most or all of your oil via the dipstick tube. Your situation sounds much smaller scale that that, though.

Answer 2

I know this is way too late to help the OP but this is for anyone landing here for the same issue. The others had good points ahead of me but as I've recently found there are other scenarios such as a bad head gasket.

The unexpected rise of fluid level could indicate it's been displaced or added to. One way this could happen is that air/combustion byproducts are escaping from a cylinder. This would hint at a head gasket/head leak where combustion leaks to the oil. Most likely the oil would look frothy or burnt, certainly not normal. It may smell burnt too. This one isn't very likely since the pressure shouldn't effect oil level without a few other issues. Just covering the angles.

Another, more likely way a head gasket leak could cause this high oil level would be a coolant leak to oil. If so this would also cause the oil on the dipstick to look milky and should definitely smell like antifreeze.

Lastly, as another responder (P s 2) mentioned, there could be excess fuel getting into the oil, so not a gasket issue but there's a way you can check for that yourself too.

If gas is mixed in you'd likely smell it but you could also try the match test. Gas should make the oil on the dipstick fairly flammable. Normally that oil on the end of the dipstick will not easily catch fire, even if you hold a match to it. If there's much gasoline mixed in it will flare up like a marshmallow in a campfire.

Well, hopefully it's not the head gasket. Good luck.