Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Burning oil or something else

Hi, everyone. I’ve tried explaining this to mechanics and they’ve all looked at me like I’m nuts. Finally, though, I have a video (should be attached to this). This is a hard phenomenon to emulate at a repair shop because it only happens the day after doing an hour (or more) of highway driving. It won’t happen while doing the driving, like if I stop at a gas station for a minute. I’ve got to do the driving, park at my destination, let a good amount of time go by (e.g. overnight) and then start my car. The smoke smells burnt, not sweet, and lingers in the air if it’s not windy.

I’m definitely losing oil, but I’m not sure if it’s a steady leak or if it’s worse in certain circumstances. My engine makes obnoxious noises that used to be intermittent but are now standard… and they’re hard to describe. While driving, from inside the car it’ll sound “rough”. When I punch it, like when speeding up to go onto a highway, it’ll go away… until I stop accelerating, and then it’ll come back (and sounds like it’s related to RPM’s… like it changes as the automatic transmission shifts). Sometimes a thing will happen where after about 30 minutes of consistent driving at 55+ mph, my engine will make a rapid clicking noise, like the freewheel clicking of a bicycle, and this fluctuates w/ acceleration. I can make it stop by pulling over, stopping my car, waiting about 10-15 seconds, and starting back up. Sometimes it’ll just decrease in intensity, but all I have to do is shut off my car and restart again and it’s gone. I suspect that all these strange engine behaviors are connected to the day-after-highway-driving-smoke in the attached video.

Any clues?

My car is a 2000 Infiniti I30 with about 175k miles on it. Thanks!

It looks more like steam to me.

Diagnosing from afar is always problematic, but here goes…
I think that this engine is a victim of oil sludging, as a result of oil changes that were not frequent enough.

If oil sludge is preventing oil from returning to the crankcase (after being pumped to the area of the camshafts), this could explain the noise and the smoke and the need to add more oil frequently. By turning off the engine and waiting for 10-15 seconds, some of the oil that is trapped in the upper engine area can drain back to the crankcase.

I hope that my speculation is incorrect, because if I am correct, then your engine has already sustained serious damage from oil starvation. Have your mechanic remove one of the valve covers in order to check for the presence of oil sludge.

If he finds what I think he will find, the only solution is to tear the engine down in order to clean it out. However, that would not turn back the clock on bearing damage that has already taken place. And then, there is the question of how much money to spend on repairing a car that is already at least 12 years old.

Related to my speculation, what can you tell us–specifically–about the maintenance that this car has received? And…how often do you have to add oil?

Another thought may be a clogged up PCV system. This system is designed to prevent crankcase gasses from escaping to the atmosphere by sucking them into the intake system to be burned. The PCV valve can be easily clogged and plug the system. Then, the crankcase will build pressure until a seal gives and allows the pressure to escape, usually with some oil. Also, the pressure build-up forces oil into the cylinders, causing an increase in oil consumption.

Usually, just replacing the PVC valve will fix this problem, and a new valve is about $5.

Busted Knuckles makes an excellent point.
Check/replace the PCV valve before plunging any deeper into the project.

Maybe you will luck-out with just a PCV valve, which is a really, really cheap part.
But…if the PCV valve is gummed up, you will also need to thoroughly clean or replace the hose leading to the PCV valve.

Check and see if your air filter box and it’s plumbing has any oil residue in it…It should be dry all the way up to the throttle plate…

I can’t thank you all enough for these responses. I’m pretty ignorant when it comes to cars, but I try to learn what I can whenever problems like this arise. The suggestions you’ve given will enable me to give my current mechanic some specific directions. I’ll also bring these ideas up with my older brother – he’s worked quite a bit on my car.

VDCDriver – For the past year and a half I’ve gotten lax on regular maintenance, mostly out of frustration (why keep putting money into a car with problems I can’t resolve?). I purchased it from a used car dealership in 2008 and gave it a thorough once-over with a friend who maintains his own vehicles and repairs helicopters and such in the army. I brought it in for oil changes and stuff for a couple years after that. The engine got close to overheating a few times when sitting idle in hot weather with the air conditioner running; replacing the radiator solved that problem.

Sorry I can’t be more detailed. As far as adding oil, I don’t have to add it very frequently (between oil changes). It doesn’t seem like a steady leak, but I also haven’t noticed a strong correlation w/ heavy highway driving.