Higher Grade of Oil can Plug Leaks?

I have to add a quart of oil every 1.5 months. Someone told me that a higher grade - or maybe it was a synthetic grade - could plug-up small leaks. Is this true? Thanks.

Year make and model might help, however, a car using some oil is fairly normal, and your dealer will most likely tell you that up to a quart in 1000 miles is “normal”.

High mileage oils are advertised as possibly being able to lessen leakage due to seals. There are additives in these oils that swell the seals. Sometimes they work sometimes they don’t. My experience has been that they mostly don’t.

Someone told me that a higher grade - or maybe it was a synthetic grade - could plug-up small leaks. Is this true? Thanks.

Wishful thinking. Use what the manufacturer specifies. Check the oil on a regular basis, as the manufacturer certainly specifies and keep it near full. While checking, fill the windshield washer fluid and check other fluid levels.

The oil can either be consumed by the engine or it can leak out. Any leak evidence . . . drips, puddles, under the car ? A quart of oil in 1 1/2 months isn’t bad at all, regardless of miles driven, but could be problematic if you don’t drive very much and suddenly take a long trip or start driving more.

The important thing is to never let the oil level get too low (more than a quart or quart and a half low). Engine damage can result.

How many miles are driven during that 1.5 months that a quart of oil is consumed/leaked ?


A quart every 1.5 month may simply be normal consumption. How many miles travelled?

They do sell high mileage oil that include additives to swell seals and they work in certain situations. However synthetic or other “high grade” oils do nothing but cost more in your situation.

I would stop worying about oil consumption of that magnitude. If by “Higher Grade” you mean higher quality, the answer is a resounding “NO”. A cheap 5W30 oil behaves the same as a synthetic 5W30 under normal driving conditions. Only with very fast driving and the engine running hot does a synthetic equipped car use less.

If you mean a “High Mileage” oil, as sold by some companies, the answer is “maybe”, since these oils have seal thickeners, thus controlling minor leaks. If you are currently using a 5W20, you can consume less oil by going to a 5W30, which is a “Heavier” oil, i.e., it’s thicker. However, don’t do this if the manual specifies 5W20.

I think the OP means higher viscosity, like 10W50 or something like that. While those will reduce leakage and consumption, you also would not get good lubrication from them, unless your manual calls for them for the temperature of your locale.

1qt every 1.5 months, would help to know how much you drive in that periods. If close to 1000 miles then you are in normal range.

Well, I don’t drive a lot. It’s less than 500 miles for whenever I have to add a quart. And I live in St. Louis, Missouri (if that is of any consequence…and it will be if we have a harsh winter here and I have to add a quart of oil to my ungaraged car.)

Although the theory of the thicker oil not leaking as easily may sound good on the outside…
Think again on the inside.

Too thick of oil may not flow INSIDE the engine’s passageways, galleys, and spaces as it is supposed to do.
Resulting in major engine damage overall. :((

Back in high school, I had a 63 Corvair that leaked oil via pushrod tube seals. It also meant oil fumes would come out of the heater. I remember adding 4 cans of STP to the engine. The oil leaking slowed considerably.

If the engine or car is on its last legs, then use whatever “band-aid” works for you. Thicker oil is one of those band-aids.

As others have noted, using thicker oil on cars you care about will have negative side effects.