I live in Az and to help with a little oil leak and a slight rocker rattle, I bought castrol High Mileage 20w50 oil. I normally use Mobil 1 5w30 but heard in this hot climate I can use thicker oil and will be ok. Any thoughts or recommedations please? Thanks.

 

People generally use thicker oil when their oil pressure falls off due to tolerances getting out of spec. In your case if that was my motor Id seal off the leak and tighten up the loose rocker... then go back to 5w30.

 

The 20/50 will be fine in your weather.

 

M1 specifically in 5w-30 or 10w-30 is VERY thin, if you like M1 try 0w-40 or 5w-40, other brands are great in 0w-30 and are much thicker in that weight. I know that sounds wrong but I am refering to operating temp viscosity the 30 number which is a RANGE not an exact measurement. M1 falls at the bottom of the range and the LT1 prefers a thick 30 to a light 40, so while M1 5w-30 is too thin, amsoil of Castrol in 0w-30 are great. Overseas the LT1 was speced for 15w-40, the 5w-30 spec we got was Corporate Average Fuel Economy driven, but I wouldn't try as high as 20w-50, I would worry about that damaging the oilpump drive.

 

I think your engine is going to run hotter and less efficiently.

Fix your actuall problems and quit trying to crutch them with think oil. It wont work AND it's a bad idea.

Furthermore, if you want a thicker oil, try 10w-30. Don't jump from 5w-30 right to 20w-50; it's just silly.

 

That needs to come with a more specific recommendation as I already covered the second number is the one to be concerned with and is a RANGE. I have seen some tests as putting 10w-30 M1 as thinner than the already too thin M1 5w-30 and both are a lot thinner than Amsoil 0w-30.

The 10w-30 is thicker than 5w-30 is a very persistant MYTH and demonstrates a lack of understanding about what these numbers are and mean. Go here to learn a little and dispell those old myths. http://theoildrop.server101.com/cgi/ultimatebb.cgi

 

I'm probably gonna switch to 0w30 all year *Castrol German stuff* from my Mobil 1 10w30. I don't know much about oil...But the Mobil 1 5-10w30 has never given me any problems, and seems to give me great performance. Without a whole debate/argument...Which oil brand and viscosity should I use.

 

I have nothing but good things to say about Mobil 1 in the 0w40 viscosity. My LT1 really seemed to like it.

 

I think I'll switch to that my next oil change.