I know that Ford says to put 5W-20 oil in GTs but I have heard that it's just because they wanted to hit emisions standards and 5W-30 will result in longer engine life. Is this true?

 

I heard that it's because the clearance of the main bearings in the engine are so tight that the thiner oil is required in order to get in to the bearings. In other words, if you use 30 weight oil then you could blow up your engine! :notnice:

You might want to do some searches and call customer service and be SURE! :angry:

Don't just take somebodies advice, it's your car. :nono:

 

I'm using Castrol GTX 5w20 in mine. I used that in my '02 Ranger 3.0 with no problems.

 

I'm using Mobil 1 5w20.

 

Thanks, I'm going to stay with 5W-20

 

If you like your warranty, stick with the 5W-20.

 

That's a little silly.

I've been using 5-w30 synthetic since 1500 miles (now have 9000 miles) and it runs like a champ. The difference in viscosity is marginal. Use it at your own discretion.

This statement makes a good point about oil weight:

"At cold temperatures, the polymers are coiled up and allow the oil to flow as their low numbers indicate. As the oil warms up, the polymers begin to unwind into long chains that prevent the oil from thinning as much as it normally would. The result is that at 100 degrees C, the oil has thinned only as much as the higher viscosity number indicates. Another way of looking at multi-vis oils is to think of a 20W-50 as a 20 weight oil that will not thin more than a 50 weight would when hot."

I live in a very hot climate, so the weight difference doesn't worry me.

 

I have heard the same about the bearings, etc. from a "Master"/SVT Technician at the local Ford Service department. A buddy of mine is a service coordinator at this dealershipalso, so I get good information from the service personnel.

I use Mobile 1 5w-20.

later,

 

If Ford finds out you are using anything but 5-20 kiss your engine warranty good bye. I use Mobil 1 5-20 , For the money its the best oil, I' m sure red line, amsoil, and lucus are very good, but more money, are they worth more, probably not. Just mine 2 pennys worth.

 

It's not silly. The owner's manual says to use a 5W20 that meets Ford specifications. If you use anything else, Ford can void the engine warranty. Use the 5W30 at your own risk.

EDIT: This is a DIRECT quote from the owner's manual:

 

Okay, I guess the makers of Amsoil have no idea what they're talking about then: http://www.synthetic-motor-oil-air-filters...ommendation.htm

 

WOW, as if worrying if my off road x-pipe, K&N drop in filter, multiple computer flashes, frequent trips to the drag strip and my future KBSC were going to void my warranty, now I have be concerned about running 5w30 oil!

My engine warranty is too important to me to risk it, I'm gonna run what ever big bro, err, I mean Ford tells me to run in my car, regardless if something better comes along. I mean, they can obviously run expensive tests to see what type of oil you have in your car right? Administer lie detector tests, maybe toss you in jail till you confess you're running a different oil. Nope, I'm not gonna risk it.

Hmm, I wonder if my 17X9 aftermarket wheels voids my suspension warranty....or washing my car at the car wash voids my paint warranty...will too much ac/dc and black sabbath void my shaker warranty....I don't even want to think what that 100 octane gas I run on the weekends will do for my warranty.

 

Agreed, I'm not going to be a slave to the man....

 

Amsoil doesn't warranty your Mustang, Ford does.

 

If you don't use the correct oil, the warranty is void - end of story. Of course, I'm sure you'll dazzle Ford with your razor-sharp wit ( ) and they'll forget all about it!

 

The bearing clearances are the same as the older 4.6L engines that used 10W30.
When Ford changed the oil in their engines we still used the same parts at the Factory to build the engines.

 

So tell me, how does ford know I didn't use the correct oil?

 

All they need is sample of the oil in the engine at the time of failure to send to a testing lab.