Do I Need To Change My Oil?

My car has a slight oil leak (pan gasket). I have to add a pint every month. Since I drive about 7000 miles/year, I figure that I would ad the sump capacity (4 quarts) every 8 months. This would indicate that I am getting (essentially) an oil change every 5000 miles or so. So can I dispense with changes and just keep adding oil?

Yes, you still need to change your oil. You may be adding fresh oil but it’s being mixed with the dirty, worn out oil that’s already in the engine. Beside that, by doing what you are doing, the filter is not being changed. You need to get the filter changed.

…And replace the oil pan gasket. It’s not an expensive repair and you’re leaking oil every-goddamn-place you go.

two things determine the need to change motor oil:

  1. level of suspended contaminants,
  2. depletion of the additive package.

your strategy addresses neither. #2 is the more critical; a key part of the oil’s additive package contributes to the oil’s Total Base Number (TBN.) When an engine runs, combustion gases contain carbon dioxide and oxides of nitrogen, some of which push past the piston rings into the crankcase. when these gases combine with water, they form carbonic and nitric acid which then collect in the motor oil. The oil’s additive package gives it mildly basic properties to neutralize these acids and prevent them from degrading metal parts. when the alkaline additives are used up, the oil is shot. adding a pint every so often does not replenish these additives adequately.

This is the sort of question only you can answer.

Why wouldn’t it? Instead of waiting 8 months and then replacing everything with 8 new pints of oil, what’s wrong with draining a pint every month and replacing it with a new pint? How does that not replenish the additives? How does that not remove suspended contaminants and replace it with contaminant free oil? In the long run, wouldn’t we expect the oil in the crankcase to have additive/contaminant levels consistent with 2500 miles of use?

The filter would still need to be changed periodically, but if the oil is being changed on a continuous basis (instead of all-at-once every 8 months), I’m not seeing the problem.

If OP wants to be sure he should get his oil tested.

Having said that, I will second QuickSilver’s remark: get this leak fixed. your car is degrading the environment and creating hazardous road conditions. If you are unconvinced of the latter, get on a motorcycle and try keeping your legs under you when you’re stopped at an intersection or tollbooth where cars have been drooling oil onto the pavement.

As usual, the answer to this type question, when properly formulated is “it depends.” The way you asked it, the answer is “yes,” but when? JZ7817 begins to explain the issue. Understanding the factors involved answers the question “when?”

It’s hard to say for certain without an oil analysis test, but in your case, it’s safe to say you can at least double the recommended oil change interval, assuming the car is in good running condition. Typical oil filters easily last 2 intervals under nominal conditions, and you are replacing enough oil to keep the lube specs up where they need to be.

One pint a month driving 7K a year is a quart every 1200 miles or so. That is one hell of a leak.
So Captain Hazelwood, have you considered you might be burning some of that oil that will add to the contaminates in the oil?
If I were in your shoes, I would fix the leak and then reassess the oil consumption of the engine.

The beauty of this method is that, over time, you find you’re adding oil more and more frequently which keep your oil even fresher.

yes…and you should give strong consideration to using public transportation

The TBN that jz78817 is talking about comes from the detergent. As the TBN in the detergent neutralizes the acidic byproducts of combustion, more sediment is created. The amount of soap in engine oil has a limited capacity to suspend sediment - and your (and ralph124c’s) scheme never reduces that amount of sediment.

The oil is leaking out. The sediment, not being fluid, is happily depositing around the leak point.

Think of it this way: you have a bucket full of clean, soapy water. You put in a bunch of dirty dishes. Then you take out the dishes, and 1 cup of the dirty soapy water which you replace with more clean soapy water. Then put in more dirty dishes, and repeat. How many times do you do this before you’re not willing to eat off the “cleaned” dishes?

… And that’s not even accounting for the other additives in engine oil that get depleted as they work. Those are increasing the loading on the dispersant - which, of course, functions by suspending such things much like the detergent does so that when the engine oil is changed, nothing deposits on your engine surfaces.

Fix the leak, and change the damn oil.