I use either Mobil 1 or Pennzoil Platinum 5w30 in my 6th gen 3.4l

 

I'm thinking of switching to semi synthetic in my 03 Monte - not high mileage but doesn't get driven much. I use Motorcraft oil in the Stang and that already is semi synthetic so that's what I'm sticking with.

 

I use Mobil 1 but think it does not matter what you use. Synthetic, conventional or a blended oil are all good as long as you follow the manufacturers recommended service interval

 

I use Castol GTX High Mileage part synthetic in the truck and Valvoline High Mileage non synthetic in my car. Car gets the oil changed every three months though and I rarely put miles on it I've put on a little over 2,000 miles since I bought it. The guys on the Ford forum are a tough crowd I'd told them i did an oil change with the oil and a K&N filter and its like the world just ended. A member told me he had cut open a K&N, Fram, Wix, Purolator and Motorcraft oil filters and the only one doing a good job was Motorcraft so everyone on there told me to only use Motorcraft oil and filters. Touchy guys there I've put 12,000 miles on my truck with no issues whatsoever. Forgot to mention the truck gets the oil changed every 3,000 miles or 3 months whichever comes first.

 

I use sae 10w30 Quaker State Motor Oil ..

 

I use nothing but Mobil 1 Synthetic in my Monte, have since it was new. I am a firm believer in synthetics.

My Dad and I switched his 1989 Chevy truck with the 5.7L to full synthetic at 200K (maybe 195K) and it's been roughly 5-6 years since we made the switch, and the truck now has 232K on it and it runs great. In fact, the synthetic helped clean up some of the oil deposits inside the engine.

 

What engine do you have 305 or a 305HO
If it's a 305 put 10w30 conventional in it the cam is a flat tappet an most synthetic oils does use enough zinc(I think it's zinc)you'll wipe out a cam lobe with syn.
The flat tappet cams are soft an weak in 305's.The 305HO is a roller cam there much better syn works fine with them.As long as the mileage isn't too high.
I think royal purple is one of the few syn oils that will work with a flat tappet cam.I use 10w30 royal purple in mine.
An full syn castrol in jess's cavi

 

Honestly im not too sure which one it is. Its an 88 ls

 

For those older engine you gotta know.I made that mistake with one of my cams before.I pulled it out an the lobes were scoring up.Only had about 4000 miles on it.
Some of the cam company's will say on the cam card what type of oil is ok with it.I seen a buddy buy a 69 malibu with a "built" 355 in it.The guy never told him what oil he used or type of cam in it.A few months after changing it to syn it started misfiring.Turned out he wiped a lobe out.It was a flat tappet cam.
It could been just a bad cam or the oil he doesn't know.Always better safe than sorry.
Till you know what you have I'd just run standard 10w30 but thats just me.

 

I've been using Castrol full synthetic for the last 2-3 years. First thing I noticed was that the engine ran smoother compared to regular oil.