I've been using Castrol Syntec 5w-50 oil on my two cars for the last 4 years, and it has kept both of my engines running smooth and perfect. I just bought an 05 expedition that says that it wants 5w-20 oil and I'm hesitant to make the change. First off I live in AZ temps get to 125 almost everyday in July (it was 118 today) will moving to 5w50 gum up the engine or cause any adverse affects or should I just go with it?

 

I can only hope for you that the engines you are running a 5w-50 oil in are foreign made. That oil is far, far to thick for a new American made engine. About the Ford, the drain holes in the upper section are towards the small side. While it is great for the specified oil, a 50 oil at temp is not going to drain fast enough at speed and you could pump the pan dry as all of the oil is in the upper section of the engine. You could also end up pumping foam. Also, rememeber your high school physics class? Thinner fluids will cool faster meaning the 5w-20 will run cooler than the thicker oil. The old thinking of running a heavier weight oil for hot areas is just that- old thinking. Todays new 929 speced oils are the real thing and a great oil regardless of the brand. You might want to look at the analysis I have posted for Pennzoil on this forum. I live in desert heat- it was 117F today and at 9:30 PM as I type this it is still over 100F. I have posted the typical environment that my engine lives in and it is far worse than harsh. I would strongly suggest staying with the 5w-20 oil. You won't put a better oil in your engine.

 

Too late I just did the oil change, I'm going to run it and if I see any problems I wil lchange it. But I did this change based on some other forums information and basically they said what I expected that it shouldn't be that much a change. As far as your post I'm using this on a Dodge Caravan and a Pontiac Grand Prix both 2001 and when i took off the intake manifold on the grand prix there was no wear down in their and the car ran perfectly. Also just so you know I'm running 100% synthetic, but here are the other links:

Oil Discussion #1

Oil Discussion #2

 

I concur 100% with Flash. Also, oils that have a wide spectrum range for viscosity (i.e: 5w50) typically come up short at the front to bottom of it's range, in other words, no oil can truly cover all viscosities in one sweep. If so, then why not a 0w60 oil?
The Syntec 5w50 oil won't ruin your engine. But a 0w20 or 5w20 oil would be a better choice. It's like having a common A-F grading scale. A oil would be the 5w20. C oil would be the 5w50. F oil is Quickie Mart's 40WT. "SA" light duty ND oil (ND="non-detergent".)
Ed

 

Before being "edukated" that "thickerer ain't always betterer" I used Castrol Syntec 5W-50 in my 1996 2.0L Zetec Ford Contour that was spec'd for 5W-30. I'm in NJ so in the winter and cooler temps it took longer for the start-up noise to quiet down. Plus my mpg and seat of the pants "get up and go" power were lower than with the 5W-30 Mobil 1 I used previously. After 2+ years I switched back to 5W-30 and all was good again . I also noticed that in the heat my cooling fan would come on much more frequently when using the 5W-50 vs the 5W-30 oil.

Whimsey