Castrol GTX 20W50

[glmoore0001]

I expect to catch some crap about this post but here goes anyway. I have 11 quarts of Castro GTx 20W50. I also have a 2006 Chevy Tahoe with 167,000 miles and pretty rusty. The vehicle that I originally bought the Castrol for has been sold. Is there any problem using this oil in the Tahoe? This is very high grade of oil and I do not want to trash it.

 

[nonickatall]

If an engine uses 5w30, I wouldn't use 20w50. That's a completely different viscosity. 20w50 is not an oil, this is resin.

That is horror for the engine at a cold start. You can see the difference at a video about viscosity's here:

It is in German, but you see at 13:20 a test, where he compare 15w50 with other viscosity's. You see the difference between 5w30, our engine need.

So don't use that oil!

Find someone to trade with, or sell the oil on EBAY and buy the right oil.

 

[glmoore0001]

Thank you!

 

[adriver]

I didn't watch the video, but the viscosity and the oil weight has to do with it's thickness. It's sized because of the tolerances in the engine specifically for that clearance. 5w30, is the recommended. 10w30 is an option depending on the temperature and wear. 20w50 is too much of a difference.

Don't think I would call it "very high grade oil". Might be able to get about half back on craigslist if you want the hassle.

It's not going to go bad if you just want to put it on the back shelf until the next vehicle might be able to use it.

 

[Mudsport96]

This time of year no I would not. Middle of summer sure. I run it in my 5.3 Silverado in the summer with no issue, but it also has over 400,000 miles on the clock. Another 100k and I think you would be fine to use it.

 

[nonickatall]

20W

This time of year no I would not. Middle of summer sure. I run it in my 5.3 Silverado in the summer with no issue, but it also has over 400,000 miles on the clock. Another 100k and I think you would be fine to use it.

20W50?

I mean the oil pump press the oil against the internal resistance that comes from the bearings that the oil is forced through. If the oil is too thin, proper oil pressure will not build up in the bearings, which are plain bearings on the camshaft, crankshaft and connecting rod.

If the oil is too thick, you will have a lot of oil pressure but no volume flow at the bearings, which is not good either. But if you drive such a thick oil and use the car on short journeys, the engine wears more than it would, with oil of the correct viscosity, because when the engine is cold, it took much longer until the bearings are proper supplied with oil.

If the engine is very worn, or is operated very hot, for example in racing, you can use thicker oil.

I would use 10W40 but not 20W50...

 

[swathdiver]

Sell it.

 

[Mudsport96]

20W

20W50?

I mean the oil pump press the oil against the internal resistance that comes from the bearings that the oil is forced through. If the oil is too thin, proper oil pressure will not build up in the bearings, which are plain bearings on the camshaft, crankshaft and connecting rod.

If the oil is too thick, you will have a lot of oil pressure but no volume flow at the bearings, which is not good either. But if you drive such a thick oil and use the car on short journeys, the engine wears more than it would, with oil of the correct viscosity, because when the engine is cold, it took much longer until the bearings are proper supplied with oil.

If the engine is very worn, or is operated very hot, for example in racing, you can use thicker oil.

I would use 10W40 but not 20W50...

You are correct. When tolerances are still tight it is important to use the recommended viscosity oils. Journal bearing surfaces are protected by the oil film, and proper flow and pressures are needed for that to work correctly. At his 167,000 miles 10w30 is most likely still fine as long as it has been properly maintained over the years. Would using 20w50 in the summer be problematic? I don't think so, I have mixed and matched oils over the years with no discernable issues. Fuel mileage does tend to suffer from pumping losses.
Get up around the mid 200k mark and sometimes the engine prefers a thicker oil. My Ford with 330,000 miles(531960km) has to have 15w40 at minimum in the summer or it doesn't carry more than 15psi at idle. 10w30 in the winter is acceptable. Get to the 400,000 mile mark and even the best maintained engine will need thicker oil, my Silverado at 413.689 miles( 665,767km) must have 20w50 in summer and 10w30 in the winter or it doesn't have good pressure.

So while I agree with you on the viscosity point, it is not a must on a worn engine. If it was me, I would use 5 quarts of 5w30 and 1 quart 20w50.

 

[PatDTN]

BMW motorcycles can use it.