The VCT Motor is very sensitive. I would not recommend going to a different Viscosity oil.

 

Manufactures spend thousands of hours and millions of dollars testing there power plants! the oil Viscosity ratings are important! to fallow!!...

 

The GT500 comes with full synthetic, 5/50

http://media.ford.com/newsroom/relea...?release=23327

 

It's really up to you. Change the oil when you get the car home from the dealer or wait 5000 miles, does not matter. What do you hope to accomplish with the use of synthetic oil?

 

Man, I changed my oil to Mobil 1 5w30 yesterday. Is this bad? Should I change back to 5w20? The guy at the oil change place said it wasn't going to be a big deal but I should probably know better than to believe anything he said!!!

 

Don't sweat it, you (and your motor) will be fine.

 

It won't hurt it, but it would be a good idea to switch back to 5-20 at the next oil change interval. I tried the Mobil 1 5-30 for a few thousand miles, I found the mileage decreased by about 1-2mpg, and it idled a little rough sometimes. Also, I had the oil analyzed by Oil Analyzers Inc. and they found the iron in the oil was a little higher than it should have been for a new engine (10K miles). Not really sure if that had anything to do with the 5-30 or not, could have still been a little break in wearing. (since the oil went in at 5K miles)

 

Thanks guys! I guess I'll just ride it out til the next oil change. Are you guys changing Mobil 1 at 6,000 miles or just still doing it at 3,000 like regular oil?

 

Ford recommends changing the oil at 5,000 mile intervals for normal driving, 3,000 for severe service. That is for the Motorcraft Semi-Synthetic oil, so you can figure if you are using Mobil 1 full synthetic, your good for at the bare minimum 5,000. I'm running Mobil1 5-20 and I'm planning on going 10K miles between changes since all of my miles are highway. (35 miles each way to work highway) But thats me, do what your comfortable with.

 

Also of interest, Ford is planning on extending it's oil change intervals for 2008 to 7500 miles for normal service, 5000 for severe service on all of it's vehicles. I figure if it's good for the 08's, and it's the same exact engine...whats wrong with doing it on the 05-07's??

 

The 2007 Ford factory service manual says to use:
5W-30 for the 4.0L V6
5W-20 for the 4.6L 3V V8
5W-50 for the 5.4L 4V V8 (GT500)

5W-50 for the 5.4L 4V V8 in the Ford GT

The 2007 Ford Falcon XR8 in Australia uses 5W-30 for its naturally aspirated 5.4L 4V V8.

 

Sorry was {thinking} MUSTANG GT not GT-500!

 

05stang raises a good point... how much of an effect does oil viscosity have on the variable cam timing system?

 

I will be following the 5k oil change routine. My next oil change is at 10k (4k between changes) so it will coincide with the 5k service intervals. Get it all done at once, multi point inspections, oil change, etc.
I can't force myself to go any longer than 5k between changes, even though after my last oil change the tech said my oil looked like I had just put it in. (5k miles on the oil)
Why do I follow this schedule, because it makes ME feel better.

 

I have researched this quite a bit. Most "experts" recommend switching over to 100% synthetic after the engine is fully broken in. Most seem to agree this is between 5k and 12k miles depending on your driving style.

This is supposed to optimize the engines performance. If you switch earlier, I don't believe you will hurt anything. It is just not the best case scenario.

Running a heavier weight oil than what is recommended will not enhance performance. Thinner oil has the ability to get into small openings better than thicker oil, providing better lubrication. Heavier oil will not break down as quickly in extreme heat situations though.

 

I have also heard from engine builders that the first 20 miles of a new engine build is the most critical due to the crosshatches in the chamber walls and the seating of the rings.

 

Granite I didn't do it the Mustang I switched the Honda over to 5w30 Mobil 1 with a Mobil 1 filter(same for Mustang) at 250 miles. Mobil 1 is what I recommend unless you can get a custom. Synthetic blends are a gimmic. They only contain 10 to 20% synthetic(usually just the additives with a petroleum basestock). There is no real benefit of running a blend.
Ford switched over to 5w20 partially for gas mileage and because of tighter tollerances in the newer engines.

 

So the 5.4L quad-cam V8s used in the Ford GT and GT500 have loose tolerances like 1960s engines and Catholic schoolgirls since they use 5W-50?

 

Why can't Mobil 1 be used for break-in or in new cars right away?

There are several car manufactures that use full synthetic oil from the factory. Are we saying that these engines never get to break-in properly?

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Not quite.. Being the engine is under more strain from boost and the fact that these engines will be run harder than your average engine, the engineers allow for that with a oil capable of a higher than average viscosity.