I live in El Paso, TX, where the temperatures can peak into the low 100's during summer. I have heard that running 20w-50 might be a good idea for that one oil change during the 3 hottest summer months because the engine needs a higher viscosity oil to handle the extreme air temperature. I run 10w-30 during the rest of the year. Is the 20w-50 over-kill??

 

Oil is heated by the engine, not the atmosphere. Your 260+ degree oil temperature doesn't change much just because the ambient air temperature has gone from 70 to 90 degrees.

 

OK, that is kind of what I was thinking ... so I guess I have fallen victim to hearing another truth-less myth. Thanks for the answer. I searched this forum, but couldn't find this topic covered. I hope this helps others who are living in the southwest.

 

We need to make this post a sticky or something. This is a very common misconception. People seem to think that if you're standing by your car sweating, all of a sudden your engine is running hotter. Your engine barely notices the difference if it's 70* or 100*F out there, it's still going to be much hotter in the coolant/oil/combustion chamber areas.

Apeiron said it well, and i'll probably be cut/pasting his quote there in the future....

 

I know I am passing this information on to the guy that told me about this misconception in the first place ... not to mention the people that ask me this question all the time too.

 

hmmm... I've been running Mobil 1 20-50 since '03... guess next oil change I'll drop down to Mobil 1 EP 10-30....

 

I believe that oil viscosity matters when it is very cold. It gets too thick at sub zero temps at start up. Once it is warm, the oil wouldn't know the difference between 0 and 100 degrees out side temp.

 

Thick oil isn't formulated to deal with extreme heat anymore than regular 30 weight. If you're actually worried about your oil getting too thin because of heat, install an oil cooler. Using thick oil to deal with this is like sticking gum in a leaking dam.

You should go down to 5W-30, it'll be better for you engine when it's cold and the same once warm.