 Re: will 5W-30 Synthetic oil hurt the engine if the engine states that it needs 5W-20
Good answer I found:
You do not need to use a 5W-20 oil. Do not let your dealer scare you by telling you that you have to use it for your warranty. That is a tactic that some dealerships use to scare customers. Once you know the facts and the Federal Magnusson Moss Act law you will be much better informed to protect your rights and use the type of oil you want to use.
The main reason 5W-20 was specified for your engine is to increase the CAFE (Corporate Average Fuel Economy) reported to the Federal Government. CAFE is the combined average fuel economy of all of a vehicle manufacturers product line. Minimum CAFE levels are specified by the Federal Government. In order for a vehicle manufacturer to continue selling profitable large trucks and SUV's, which typically have poor fuel mileage ratings, as compared to smaller cars, and still meet mandated CAFE requirements, they must also sell enough of the smaller cars which have much better fuel economy ratings to offset the poor fuel economy ratings of the larger vehicles. For model year 2001, the change to a 5W-20 oil will allow Ford and Honda's overall CAFE to increase by a very small amount, typically in the tenths of a mile per gallon range. 5W-20 oil is a lighter viscosity than a 5W-30 oil and therefore has less internal engine frictional losses, or less drag on the crankshaft, pistons and valvetrain, which in turn promotes increased fuel economy. This increased fuel economy is virtually undetectable to the average motorist without the use of specialized engine monitoring and testing equipment under strictly controlled test track driving when compared to a 5W-30, 10W-30 or a 0W-30 viscosity motor oil.
__________________ 2003 Tropic Green 3.8L:
Synthetic Oil, K&N Air Filter, MGW Billet T-Shift Handle (Pony), MGW Interior Billet Accessories , Bullitt Fuel Door, Silver Bullitt Rims, Dunlop SP 5000 245/45WR17 Tires | 
