Nissan Altima oil leak can't be found

We have a 2002 Altima. We had been hearing a rubbing noise as we drive…first between 30-40 mph, and later at higher speeds. The first time we went to the local mechanic, he said there was almost no oil. He couldn’t find a leak.

We’ve just had the car at the dealer’s. The engine oil was flushed twice, but they too couldn’t find a leak.

We’ve occasionally seen small drops under the car, or large puddles which have seemed more like water.

Any advice? THe car has 65,000 miles.

Well, my best advice is to check your oil dipstick VERY frequently from now on. Unfortunately, if the mechanic found the engine to be very low on oil, apparently you had not been monitoring the oil regularly.

While oil does not have to be leaking in order for the engine to be low on oil, since you say that you have observed fluid underneath the car, I would suggest putting a large piece of cardboard (like a box from a large appliance) underneath the car in order to be able to better localize the possible leak and to be able to examine the fluid more closely.

In addition to a leak, your engine could be burning oil. While your car has only 65k on the odometer, you did not give us any indication of how well the vehicle is maintained, and poor maintenance can also lead to premature oil burning.

Also, where it is maintained is of major importance. If you are in the habit of using “Quicky Lube”, you should be aware that their barely-trained teenaged employees have a reputation for forgetting to do certain things like–putting oil into your engine after draining the old oil!

They have also been known to drain the transmission by mistake, thereby ruining transmissions. The list of screw-ups from these places is almost endless, and several vehicles nationwide each week have an engine/transmission/differential destroyed by the ineptitude of the kiddies at quick oil change places.

Another possibility for loss of oil is a bad head gasket. If your engine was ever overheated, this is a possibility, and unfortunately, this can be a very expensive repair job. Has your coolant level dropped at all? Does it appear to be “milky” in appearance? Whether these situations have been observed or not, a competent mechanic can check your coolant for the presence of hydrocarbons from the engine in order to confirm whether the problem lies with the head gasket.

If you determine that the engine is indeed leaking oil, then replacement of one or more gaskets should take care of the problem. The labor may be relatively cheap, in the case of a valve cover gasket, or fairly expensive, in the case of an oil pan gasket or other gasket. If it is burning oil, then you are looking at a repair job that could simply involve valve guide seals or (gulp!) piston rings. And, as said previously, a bad head gasket is also an expensive repair job.

Anyway, if your engine was run with a very low oil level (whether as a result of a leak or from oil burning or from a bad head gasket, plus failure to monitor the oil level), it is entirely possible that it has now sustained enough extra wear and tear for it to burn an excessive amount of oil. I suggest that you check the dipstick every couple of days in order to see just how much it might be burning. Try to never let it fall below the “add” mark on the dipstick.

Once you determine what caused the low oil level, then you can decide whether to fix it or to dump the car. And, whether you keep this car and repair it or whether you decide to dump it and buy a new car, you should be sure to maintain your car properly and to regularly check the oil level in order to avoid the situation in which you currently find yourself.