Just FYI,
I saw that shell released a Rotella T6 5w30 "multi-vehicle" full synthetic branded the same as the 5w40 HDEO. Unsure if there are any reviews out, but it should be hitting the shelf soon

 

is t4 reg oil ok, much cheaper and its likely my jeep never tasted synthetic!!
i see shell comes in 1 gal ,not 5 qts like others

 

I bought a 2.5gal jug of T6 at Advance Auto not long ago.

 

OK guys I know this is a basic question, but I can't find T6 full synthetic in anything but 5W40. So how wrong is it to swith to T5 semi synthetic for the summer and then back to full synthetic come winter?

I feel like I should follow the manufacturers guidelines regardless of the full or synthetic blend.

 

I service 4 vehicles using T6. Around here it's always available but sometimes it's 0w40 or 5w40. I use what's available at the time.

No reason to switch for the seasons.

 

is t4 reg oil ok, much cheaper and its likely my jeep never tasted synthetic!!

 

It's great oil. I use it in everything.

 

ok, thanks..

 

Oh really? Cool, I'll keep my eyes open for it.

 

The only thing worse IMO than 5w-** is 0w-** for these old 4.0s unless one lives in the antarctic.

The prime reason for the newer engines specifying 0/5w-20/30 is to meet EPA gas mileage requirements.
Auto manufacturer's are slowly but surely waking up to the fact these low viscosity oils are reducing engine half life's.

 

You seem to think 0wXX is some kind of .... thin? You know that cold 0wXX is still thicker than hot Xw40, right?

 

Another thing you should learn about is why newer cars are calling for synthetic oils instead of conventional:

 

-35 degrees! I think I would rather die than live somewhere that it got that cold. I don't like +35*.