Is 5w-20 oil too thin for my 78 460? I've always run 10w-30. I had the oil changed today and didn't even think about it until I looked at the invoice.

 

O BOY an oil thread!!!! I'll go first... I use Rotella 15w 40 in my 460. 5w 20 is too thin for me.

 

Just keep an eye on it see it decides to drink it. If it doesn't I would let it go rather than waste it.

 

Too thin IMO... I'm in the 10w-30 and 15w-40 camp....

 

10w30 in cool weather.
10w40 or 15w40 in hot weather.

 

x2 or 10w-30 diesel oil, it's good for these old engines. newly rebuilt or not.
Or be prepared to run a zinc additive if you want to run something other than diesel oil.

 

Mazolla 15w40 isn't the preferred brand any more????????? ☺

 

Add a bottle of STP additive to thicken it up a bit and add zinc at the same time.

STP Oil Treatment, 15oz - Walmart.com

Run it and Keep an eye on it..

 

15w-40 for me. 5w-20 is asking for trouble.

 

https://540ratblog.wordpress.com/201...-test-ranking/

 

Did u even read it all?? what's your suggestion out of all that info listed? lol...

 

Yeah I read through quite a few oil pages on this subject and most devolved quickly into additive arguments. My main concern right now was the weight of oil. I did not see anyone else using 5w-20 in these engines. I will probably run it with some additive for a bit and see how she does.

 

The oil pressure gauge will tell you if it likes the viscosity. How is oil pressure at idle when hot? I like to see at least 20 psi on a fresh engine.

Agree as many have mentioned, you need some zinc if running a flat tappet cam. 5W20 would be a modern car oil which does not have enough zinc. You could add some ZDPP. My solution would be to change the oil and filter pronto and use 15W40 Rotella T.

 

It was at about 30 psi hot. It looks like modern ford trucks call for this oil which might be why they put this stuff in. Either way it's coming out soon. The only reason I brought it in was my drain pans are all full and I got lazy. Serves me right!

 

I'd just like to say shame on the shop you took it to for putting such a light weight oil in your truck. I'd imagine most lube places would know nothing lighter than a 10W30 in an older vehicle. Me personally I would change the filter and oil and use 10W40 or 30. 15W40 is also very popular amongst the guys in this forum. Myself, I run Mobil 1 10W40 full synthetic with the Mobil 1 filter which will be part number M1-301 and I use the Lucas Synthetic Oil Stabilizer. Turns out to be a fairly expensive oil change for me but hey I like the stuff and more importantly so does my truck. I use the same stuff in my 85 Stang