Rick's Free Auto Repair Advice

Heavier weight oil

Heavier weight oil – thicker weight oil

This article is about adding a heavier weight oil to your engine to stop oil leaks or oil burning.I’ve written a post on the importance of using the correct oil viscosity for your particular engine—read the warning here. The take-away from that post is to always use the oil viscosity recommended by the vehicle manufacturer.

But I often see people recommend using a heavier weight oil to solve an oil leak problem or a problem where an engine burns oil. The theory is that a heavier weight oil, since it’s thicker, will solve the leak or burning problem. But using a heavier

Heavier weight oil accelerates engine wear

Your read that correctly. Oil’s job is to remove heat, reduce friction and prevent corrosion. If you add a thicker or heavier weight oil to your engine, you actually increase friction and reduce the oil’s ability to remove heat. The result? Faster engine wear.

bottle of 5W-20 oil and heavier weight oil

heavier weight oilDoes heavier weight oil stop oil leaks?

Once again, the theory is that a heavier weight oil won’t seep through gasket openings as easily. If engine still used straight weight oil, then a thicker oil might reduce leaking. But mult-visocosity oil is thinner at cold startup, so it seeps through gasket openings just like thinner oil. Oil thins as it heats up and multi-viscosity oil resists thinning better than straight weight oil, so it winds up at a thicker consistency when hot than a comparable straight weight oil.

But let’s be realistic. If you’re engine requires 5W-20 and you want to add 5W-30, you’re really not gaining much once the engine heats up. Perhaps it might slow oil burning or leaking by a small amount, but you’re also increasing friction and wear. Switching to 10W-40 of 20W-50, on the other hand will increase friction and cold start wear by a huge amount and still won’t get you much of an advantage of the leaking and oil burning issue.

What happens if you add a quart of oil of a different viscosity to top off your engine?

The answer is pretty simple. If you had 5W-20 in the engine and you add 1 quart of 10W-30, it raises the viscosity of the crankcase oil slightly. One quart won’t change it enough to worry about. It’s the second quart that starts to change the operating characteristics of the oil. So, if you had to add a second quart of a different viscosity, you should change the oil shortly after.

This article is just one in a series. If you’d like to know more about oil click on the links below.

Choosing the right motor oil

Chrysler’s 3.5-liter engine has oil sludge issues

High mileage oil and oil filters

Oil Viscosity Warning

Synthetic Oil Facts and Myths

Synthetic oil versus conventional oil

What motor oil to use

What oil brand is best

What oil should you use

When to change oil

Best Oil filter

oil filter, wrong oil, do I have to use synthetic

Oil filter filled with sludge


© 2012 Rick Muscoplat



Posted on by Rick Muscoplat

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