I have a 2008 5.4L V-8 with almost 60K miles and have always used Motorcraft 5W-20 synthetic blend recommended by the manual. I am a believer in keeping things OEM, but I'm thinking about switching to Amsoil Signature Series 100% full synthetic for my truck. Because the Honda dealer is so far away, I started using it in my Accord and I notice a considerable difference. I'm getting better fuel economy and the car idles and runs smoother. It is really cold here in the winter and I think going full-synthetic would lower cold start wear also. What do you guys think, should I stay stock, or go with a full synthetic? If I go with the Amsoil I would probably extend my oil change intervals but still continue to change the filter every 5,000 miles. Do any of you have experience using the Motorcraft 5W-20 full synthetic?

 

If you want to switch to Amsoil, I'd use 5W20 Signature and a EAO11 filter, and change it every 12k or once a year, whichever happens first. While you are at it, get a EAA200 air filter.

 

If cold starts are the issue, you're going the wrong way. There is a test called the Cold Crank Simulator test that reflects the actual flow properties of an oil expressed in centipoise. For the Xw- 20 oils, the target temperature is -30F. So if your winter start ups are colder, let me know and I'll find the right oil for you. So here's the numbers for you. The smaller the number, the less energy required to turn the engine and the more the oil will flow.
Amsoil Signature= 4979
Mobil One Extended- 4670
Motorcraft Blend= 5200
Motorcraft Synthetic= 4000
Pennzoil Ultra Platinum= 4050

The Tritons were never hard on oils, unlike the EcoBoost series. You don't really NEED a synthetic but if cold starts are an issue, Motorcraft Full Synthetic and Pennzoil Ultra Platinum are tops. Considering the additive package, if the price of each were the same, I'd be buying the Ultra Platinum. The Pennzoil should be a real easy find at WallyWorld and probably cheaper than the Amsoil. Unless you make short trips or pull heavy loads, and you are using a major branded top tier gas, there's no reason that either won't provide you with easy 7500 mile service.

 

Motorcraft 5w20 semi synthetic is a great oil. I wouldn't switch, just change it every 5,000 to 7,500 miles depending on how you use your truck.