the oil you put in should be fine. and 5w20 is the recommended weight for ALL seasons with the 4.6

 

right in your article, it also says......"If you drive a late model car consult your owner’s manual to determine the recommended viscosity range that was intended for your car. "

Mine says 5W20 and that is all the dealer has ever put in it. Winter or summer.

I get mine changed at the dealership because I got free oil changes with my car

 

10w30 will do no harm to the motor so dont sweat it.

 

i love these kind of replies

lol

 

I'm pretty sure the engine will be fine with 10W30 in the summer weather tough I wouldn't go any thicker.
In the winter, I run mobil 1 0w20 works great. If you read the box it says that it's for ford cars that take 5w20

I'm planning on switching to royal purple 5w20 for the summer though cause I prefer a full sythetic to a blend.

 

Get a different oil cup and it will say 10W30. My old remeo said 10W30, I used to put in it 10W40. Read that article, it was written by Ford techs. First number is startup second is high temp break down. 20 is a little low, you will exceed that easily during hard driving or racing.

 

but the one that comes with the car is the one that matters...
btw, 4600, thanks for the maf vs. s/d info. interesting stuff to know

 

ok lets get some things straight here. lets compair 5W20 to 10W30. the first number means the oils viscosity at cold temperatures, the lower the number the thinner it is. Now the second number is the viscosity of the oil at operating temps, same applies here lower the number the thinner it is. i have no idea how they test the viscosity of the oil and assign it a number and dont really care. but 5W20 is a overall thinner oil at both cold(prestart) and running temps(hot) then 10W30. now in the car manual it says 5W20 so use 5W20. Enough said.

 

That 20 means it will brake down at lesser temperature, and thus form sludge.

 

As you can see, alot of people don't really know the answer. They basically stick with the manual because, well, they just don't know any better, they've never tried it, and have no idea what would happen. I've run 0w20, and 5w20 in my mustang. However, in other cars I've had, I've run thicker in the summer and thinner in the winter as per my mechanics instruction and the car lasted to well over 290k miles where, the problem that occuered had to do with the radiator/cooling system, and the car made it to the shop at very high temperatures (it couldn't hold coolant more than 2 miles) without actually damaging the motor. The only reason I junked the car was because it wasn't worth a new radiator and clutch both of which it needed badly (it was a 94 saturn in really crappy condition), but the engine was fine. I attribute the engine not seizing on my way to the shop to the fact that I was using thicker oil (cause it was the summer) which suffered less thermal breakdown.

Anyone running lightweight oil in superchaged GTs or V6s where you have a wimpier radiator and no heat extractor hood, should think about doing an oil cooler install. I'm pretty sure cobras came with one.