I buy 10-30w synthetic, it's the cheapest because that's what everyone consumes the most of trying to find 0-40 synth is almost impossible, and not neccessary for 70-90 degree climate.

 

I usually find my Mobil1 ow-40 at Walmart for about 6.50 a quart.
I usually buy it if it's there so I'm ready for my next oil change.
Stan

 

I agree with Harbor, it may cost you the price of the oil, but the piece of mind is worth it.
I always use the factory recommended 0w40, but 5w40 should be fine as long as you don't live in the North Pole.

 

Don't forget to consider the amount of sulfur and phosphates and different formulas. I considered using the 5W-40 Mobil 1, which has a significantly higher film strength- made possible by utilizing more of the sulfur compounds. The problem with this is these additional sulfur and phosphorus compounds make their way to the catalytic converters, which weren't designed for the excess "pollutants" which reduce the efficiency of the catalyst and you essentially kill your catalytic converters. Wonder how many people have had to replace their cats because of this?