I think the absolute best oil for topping up is more of what is already in there. Then there are no issues with incompatible additives. So go with Motorcraft synthetic blend 5W-20 for a GT. BTW, Ford does not recommend topping up unless the oil level is below the lower hole on the dipstick.

 

I gonna have to call you on the "don't use synthetic oil until you have more miles on the engine". Where are you getting your info that synthetic can't be used or will cause harm to your engine when your milage is low or new?

 

If the oil level is between the MIN and MAX values, then don't touch it. Filling your oil over the MAX line is more dangerous than it being slightly below the MIN line.

 

I never said it would cause "harm" your engine. I am well aware that many cars come with synthetic oil as brand new cars, I have had cars with Synthetic as new. Mobil 1 even says on their website that you can use or switch to Mobil 1 at any time.

This was simply my opinion as I have had problems in the past with using synthetic too soon and had seating and blow by issues. It is also said that with newer engines (say 2000 and up) it is not as much of an issue as with earlier model engines. I error on the side of caution because of my personal experience. Please just take it for what it is worth to you and if that is nothing, you are certainly entitled.

 

evry 3,000 miles?

Isn't it overkill getting oil changes that often? Ford recommends every 7,500 miles for my 2008, unless I'm reading the wrong service manual that came with my car.
Or are you using basic dino oil?

And the 5W20 is for the 4.6lt engine. 4.0's will use 5W30

 

Every 3000 miles unless it's severe duty is probably a bit on the overkill side even for a blend. With a full synthetic you could easily go 5000 between changes.

Some people just like to change their oil and it's not gonna hurt it to change it every 3K.

 

That depends a LOT on how you drive it. Hard cornering can uncover the pickup pretty much no matter where it's located if the oil level is low enough (and you've pumped enough of the oil up into the cam covers with high revs. I don't know if the aluminum 4.6L's sump is baffled to help control this or not.

Understand that the owner's manual is talking about driving that's quite mild as compared to the treatment that many of the members of this site expect their car to put up with. Keep also in mind that the manual is written for people who have absolutely no idea how an engine works or what it support systems it needs (lubrication, cooling) in order to live. People who don't know much more than "use the key to start it, put gas in it once in a while, and point it more or less down the road".

I would not want to rely on a low oil level being officially considered acceptable in the manual - only to have a later warranty claim denied based on use with an oil level a quart or so low then being construed as abuse.

For now, I'll buy into the thought about not overfilling it, but not the argument that suggests that being a tiny bit over "MAX" is worse than being an equally small amount below "MIN".

FWIW, if I find my oil level anywhere below the top of the crosshatched portion of the stick, I'll add enough to put it at the top of the crosshatch or slightly above. Still below the top hole, though. You tend to get "conservative" about things like oil supply once you've built a couple of engines.


Norm

 

Interesting. My guide for 2007 says 5,000 miles, unless I'm reading something wrong. I wonder what they changed from 2007 to 2008 besides what the manuals say.

 

I find it hard to believe that synthetic oil caused your seating problems and blowby. There's nothing I've seen, read or come across to suggest that synthetic causes these problems. What mechanic did you go to that led you to believe that?

 

Try Wikipedia, not that they are all that reliable. They have a write-up about synthetic oil. In short, they say that a certain amount of friction is needed for proper engine break-in. They acknowledge that some cars come from the factory with synthetic, and that even if they don't, the use of synthetic during the break-in period is not necessarily bad for modern engines.

Personally, I wouldn't use synthetic until about 10,000 miles unless I lived on the North Slope of Alaska, in the Sahara Desert, or some such place. Or if I had some other compelling reason to do so. I wouldn't do it "just because."