It is NOT a Trans Am and NOT a Formula
It has the L03 5.0L V8

The book recommends 5w-30 for all temps
10w-30 is ok above 0
straight SAE-30 is ok for 40+

but l also know that the 20 is can get better gas mileage and is used on may newer cars.Ford even retroactively recommended 5w-20 back to 1991 on most of their cars with only a few exceptions (v8 SHO is the only one that l can recall now).There is also a controversy on whether or not the 20 is enough to protect the car.

This is why I am unsure though

help me out if you can
engine does not leak or burn oil
running fine

5-20 for winter 10-40 for summer

No, it is not. It would be foolish, l will go that far.

The idea of using 20 weight oil in cars with pressurized lubrication was not even thought of for a decade after the car was built.

Bad idea.

Use what the manual recomends. 5W-30. l have a 91 GTA. l use 5W-30, which is exactly what it says i'm supposed to use. The way l see it, if you wanna have a V-8, screw the gas prices, go for it. So in your case, do what the book recomends. If you'd want to save on gas, you'd have a shitty V-6.

You certainly can use a 5W-20 or 0W-20 if u choose to, however u do not need to use a 5W-20 or 0W-20 oil. You do not have to use 5W-20 or 0W-20 to maintain ur warranty, even though some dealership personnel may lead u to believe that u have to use a 5W-20 or 0W-20. Your warranty is still valid & has to be honored whether u choose to use a 5W-20, 0W-20 or another viscosity of oil, such as a 5W-30 0r 0W-30 for example.

One of the main reasons 5W-20 & 0W-20 was specified for ur 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 r specified by the Federal Government. In order for a vehicle manufacturer to continue selling profitable large trucks & SUV's, which typically have poor fuel mileage ratings, as compared to smaller cars, & 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. The change to a 5W-20 or 0W-20 oil will allow & an auto companies overall CAFE to increase by a very small amount, typically in the tenths of a mile per gallon range. 5W-20 or 0W-20 oil is a lighter viscosity than a 5W-30 oil & therefore has less internal engine frictional losses, or less drag on the crankshaft, pistons & 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 & testing equipment under strictly controlled test track driving when compared to a 5W-30, 10W-30 or a 0W-30 viscosity motor oil.

No, do NOT switch to a thinner oil on an older car like that. Stick to what the manual tells you to use.

Those older engines were not designed for the 20w is that cars use today, and even today is cars only use that oil for emissions and mileage trickery.they really do not help anything.

Rainman, if you're going to copy info from another site at least make it relevant lol. You're talking about voiding the guy is warranty.he has a 17yr old car lol

Stick with 10w30 and you will be fine. There is no need to get all fancy with switching oils. Stick with what you've been using. l used 10w30 on all of my Fbody motors and had them last a very long time :)