I have a case of really good syntho 5w/30 oil. My 03 Crown Vic is ready for an oil change, it calls for 5w/20 can I use 5w/30 w/o any issues?

i don't see why not.

You'd think that but my buddy used 5w/30 in his 07 Magnum (5.7 hemi) and it started flashing codes on him.

Check the owners manual. Usually they say it is OK in warmer weather.

I don't have one.... I'll "Google it".

I used to run that in a 4.6.

The MDS system specs 5w20 in the hemi vehicles.In a Ford 4.6 (especially with some miles) it wouldn't bother me a bit.

You can run 15w40 if yah want. But the drainbacks in those Fords are so horrifying it might take a while to get back in the pan.

I don't doubt that some owner's manuals state that, but its kind odd reasoning. The weather has much more effect on lubrication during cold engine startup--when the 5w viscosity comes into play.
Engines operating temps are largely controlled by the thermostat, not the weather--when the 20w or 30w is in effect.

It would make more sense to state that a 10w/20 (if one existed)can be run in warm climate than a 5w/20

I run Mobil 1 10W 30 in my 08 Bullitt mustang. rec oil is 5W 20.


motor is built but I still use the variable cam timing.

5.7 in a Magnum has MDS which requires 5w20 to function correctly.

Your Crown Vic doesn't have that stuff so you'll be good.

I ran 10w30 in my Towncar because with 5w20 the cam chain tensioners would bleed off overnight and it sounded like a thrashing machine until it pressured up.

Kevin

Thanks people.

My Wrangler called for 5w-20, I used 5w-30 in it for 80,000 miles and no issues.