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Slight oil leak


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My GMC Sierra has over 200k miles on it and I’ve been using 5w-30 synthetic oil as I always has and recently I’ve noticed a very small leak in my oil. Would it be smarter to start using 10w-30 or 10w-40 because my trucks many miles or just stay with what I’ve been doing?

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 By calling it a leak you have oil on the floor or coating your engine externally? Changing oil viscosity is very unlikely to stop a leak at a seal or gasket. Best to fix the offending part.

 

If you're burning, consuming oil internally to the engine, then viscosity might make a difference

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Like txab said, mechanically leak, ie bad/worn seal can't be fixed by a different grade oil.  Best to find it and replace the part that is leaking.  My 2002 started to leak at 170k and it was the rear main seal.  Once that was replace it was back to a nice and dry engine and undercarriage.

 

If it is burning oil and no evidence of exterior leak then a higher viscosity might help slow it down.

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If it is a seal in a motor with that many miles on it a band-aid fix MIGHT be a high mileage oil. Sometimes a seal will weep when it is loosing elasticity and a high mileage oil will swell the seal a bit slowing or even stopping the leak for awhile. How long is a while? :dunno: A gasket may be cork, composite, rubber, synthetic and may respond to the same thing but less likely to do so. 

 

Even replacing a seal on a shaft with that many miles may not solve the issue IF the shaft is also worn. Depending on where, a 'Speedi Sleeve' will often do the trick. If it worn past that parts replacement or repair will be required. It's near impossible to get a new seal to seal on a worn shaft no matter how well you prep it. 

 

After all that....repair is a better solution. Heavier oil will do nothing meaningful. 

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you might want to look into your oil pressure sensor, when they are on the down side they can leak oil, its discrete at first, and will be toward the firewall side.  Put your hand back behind the engine and see if you have oil slick residue back there, then change it out before changing oil types. 

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