We all know it says 5w 20 on the oil fill cap.

Will I cause damage by using 5w 30?

 

If you have a 5.4 I would not switch to 5w30. The VCT system works on oil pressure and using oil not recommended by Ford could eventually cause damage to the engine. Check the video link in my sig.

 

no damage if you do your oil changes regularly, however better viscosity will be provided if 5w20 is used rather than a bigger spread number. So maybe your engine if run right and properly will last longer by using 5w20.

 

thanks.

 

Itll be fine, it will not prematurely wear your engine out.

 

Exactly!

 

There is very little viscosity difference between 5w30 and 5w20, so you will be fine either way. 5w20 is a better oil and a better choice.

 

Things that will damage or eventually do harm to your engine are: Using cheap oil, going too long between changes or not changing it, flooring it from a stop, prolonged hi-rpm use, and running it out of coolant. People have used 15W40 in these engines and had them last hundreds of thousands of miles, so using a slightly heavier oil is ok. If the VCT system runs off of oil pressure, how does it know the difference between a 20, 30, or even a 50 wt oil as long as it reaches the correct pressure to make the system function?

 

Ive been running 5w30 for about 40k miles.

 

I have never understood why you would want to run anything other than what Ford recommends. They decided on 5-20 Motorcraft as best for these modular engines, it's cheap and readily available, so why not use it? Something else may do ok, but why use it? It just gives them another excuse to void the warranty if you have an engine problem.

 

I suppose the 5w30 guys don't know about the 5.4 VCT system.

 

Thats exactly what I was thinking. People ask all the time if they can run a different weight oil, but why? There are potnetial down sides to running a non-recommended oil, but no up sides. So whats the point?

 

I would not run anything but 5w20. I just spent $2500 on the heads. The reason the valve guides wore out is because the previous owner was not running the correct oil. Think about how far it is up to those heads plus path is tight to get there. With Iowa winters and the wrong oil the heads could be running without oil til the engine was good and hot. Take it from me, use the oil that Ford recomends. The engineers may have been on crack when they designed it but running the right oil will save you money in the long run.

 

The 5 in the 5W-whatever is the cold temperature flow weight, so it doens't matter what weight you use. As long as its a 5W-XX they will flow the same at cold temperatures. If an engine part is going to wear out prematurely, it will no matter what anyone does. Hundreds of people have had issues when running nothing but Motorcraft 5W-20, while others have run that same oil with no issues at all. Generally the only time an engine will fail because of oil is when the owner doesn't change it or runs it too low on oil.

 

But still, when Ford engineers recommend 5w20 why would you change? Is it because you think you know more than them?