Will thinner oil damage anything when it is burned?

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952
Location
Erie, PA
I have a few higher mileage vehicles that burn about 1.5 to 3 qts in a 3K mile interval if you use 5w-20 synthetic. If you bump up to a 5w-30 or 10w-30 conventional, it will slow down but frankly I have not monitored it to remember. I just scored a huge stash of 5w-20 and am wondering if by the act of the engine burning more oil will hurt anything. I will always keep up on the oil level as im OCD and always keep them full. If you need to know the oil consumption is from the valve seals, and it is a MAJOR job to do it and just not worth it. Vehiceles are mint otherwise.
 
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4,030
Location
WA
You risk increased fouling everything in the exhaust stream as well as a dirtier combustion chamber which <span style="font-style: italic">can</span> lead to "octane creep", you'll have to Google that one.. Whether or not that translates to "problems" for you I guess depends on how long you decide to keep the car but eventually you'll see signs of the oil burning if you keep it long enough. Maybe you can work your way through the stash of 5w20 by blending it with a thicker lube?
 
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Messages
2,273
Location
Cincinnati, USA
The short answer is yes, don't use that oil in those vehicles. Whatever cost savings there was, probably isn't worth it since oil does not go bad rapidly so you should have the opportunity to use it in other vehicles.
 
Messages
5,361
Location
Paramount, California
If thicker oil helps, definitely use a thicker oil to reduce severe oil consumption. You can even use 15W-40. It sounds like you may have bad valve-stem oil seals, which are very sensitive to KV100. Yes, excess oil consumption will foul the spark plugs a lot faster, and it could damage the catalytic converter, oxygen sensor, and particulate filter. Wonders of valve-stem oil seal replacement
 

Fordiesel69

Thread starter
Messages
952
Location
Erie, PA
Yes it is the valve stem seals. Dont have interest in changing them as the vehicles have 170K, 191K, and 193K. So to do the job is 12 - 18 hrs for a home mechanic, and on my F150 its not possible due to severe rust on everything in the engine bay. About $300 more in tools. Just not worth it as our local cab company stated they ran these engines 300-500K miles and just topped oil every day. They claim the engine will not wear out just because it used oil. And none use more than 3qts in 3000 miles. And that is only during very hot highway commutes at 75MPH.
 
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