20w50 in a 99 Suburban 350

[Cole Leyden]

I have a 1999 suburban with 190k on it. It’s a wonderful car. The rear main has just started to slowly seep. I have been running 20w50 in it for about a year now. Is there any benefits by using the thicker oil? I live in So. Cal. Since I’ve been running it, it’s been much more quiet.

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[Dave Tidman]

You should always run the recommended oil weight. I might try a high mileage oil, they have seal conditioners in the oil.

[Jim Chandler]

I’ve done the same thing in the past. However, I found that, although it can quiet things down and remove symptoms like some minor leaks, it ultimately will accelerate engine wear. Consider, the heavier oil takes longer to circulate than the intended weight oil. You might buy some time with it, but I would plan to deal with the rear main seal before too much longer.

[Richard Kirshy]

That is some mighty thick oil to be running as a band aid for an oil leak and not the best thing for a 20 year old engine.
If your not planning on replacing the rear main seal..
You might consider adding Marvel Mystery Oil in with your next oil change ( follow the recommended amount usage ) and recommended oil.
Several changes may help soften the seal and slow the leak.

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