Synthetic Vs. Non-Synthetic Oils and Fluids


What's better and why?

Pros and Cons of each?

What brands are better and why?

If you have links to add to your facts please add those also.



I'm getting ready to do a 4.0L over haul/budget rebuild. And looking at all my options...

 

Well I personally think that synthetics are better. However, it seems that people in the jeep community havnt had the best of luck when it comes to synthetics. Apparently the 4.0s do better with non-synthetic.

If I was doing an engine overhaul I would honestly just use diesel oil. 15w40. Diesel oil had zinc in it which prevents internal wear.

I use 5qts 10w30 castrol and 1 qt lucas oil stabilizer. Lucas oil stabilizer is amazing stuff. I would look into that if you haven't already.

 

i use mobil 1 10w30. works for me

 

Shell Rotella 15w40 is what I've also been looking into running as well.

Just looking at all the options seeing as engine over haul will be happening starting late next week..

 

I run 15-40 it quiets things down a bit. 240,000 will give you some ticks.

 

Here's some motor facts, not opinions, and some motor oil myth busting also. The second link gives excellent reasons why thicker oil is not better.

http://www.google.com/custom?q=synth...f&oq=synthetic

http://www.supramania.com/aehaas/

 

Some interesting info there I'll be reading through. Thanks for sharing that info..

 

From everything I've read... running synthetics is like running different exhausts. Everyone has their own opinion on whats better, and some honestly think that different kinds will blow up your jeep.

Fact #1: You can switch to synthetics from conventional and vice versa at any mileage.

Fact #2: Synthetics will not cause leaks. What causes leaks is the fact that they clean out gunk, which if your seals were held together with crud, they were bad anyway.

The benefits to synthetics are small increases in mpg as well as longer oil change intervals. The longer oil change intervals being the more significant change.

Above all, whats important whether you run synthetics or conventional is finding the right oil ratings. I laugh at people who say my grandfather ran "insert oil brand here" for 30 years so it must be better than everything else. They obviously have no clue because oil formulas change frequently. The 4.0L is a flat tappet motor, which requires a certain amount of zinc for the cam. Newer oils are rated "SM" which is meant to save fuel and reduce emissions in todays MODERN engines. These oils have far less zinc than the previous "SL" rating of former years. Certain oils such as Rotella or Mobil 1 high mileage have the right amount of zinc that you need. Running an "SM" rated oil for one or two changes won't hurt anything, but over a longer period of time it can do damage.

 

According to the American Petroleum Institute (API), SM rated motor oils are "for all automotive engines currently in use and are designed to provide improved oxidation resistance, improved deposit protection, better wear protection and better low-temperature performance over the life of the oil". SM rated oils have superseded SL and SJ rated oils. SH, SG, SF, etc., etc., are obsolete and have been since 1996. It's just a matter of time that SM, SL and SJ rated motor oils become obsolete and are replaced with even better engine protecting motor oils. I would think zinc has been replaced by some other additive, that reduces wear just as well.

 

The previous owner put synthetic blend which I do not like since I have heard water is mixed in with the oil.

Is full synthetic better for 4.0L or just regular conventional oil?

 

i think it is just personal preference honestly. this arguement will go both ways

 

Nick...

If you are interested I have some excerpts from a good book on the subject, If you would pm my an email address that will accept some .pdf attachments I would be glad to send them to.

 

Conventional oil has been used for along time. Synthetic is manmade, thats all I need to know to make up my mind.

 

here here

 

This is just a matter of opinion. I personally run Castrol GTX in both of my vehicles. ('00 XJ and '08 Uplander) I have used Castrol ever since I have been driving and have not had any problems with it at all. The arguement of synthetic vs conventional is a matter of preference. I prefer Castrol, but am not against running a synthetic. Nick - I think Shell Rotella is a great oil, and a great choice. Take lots of pictures of your overhaul and post them.