Wow, this turned into Rocket Science. I use Penz Gt in teh motor, I've always liked it.
But the book says the diffs and t-case use synthetic. Is there harm in changing it to regular. If I do, what weight should I use?
<img src="/forums/images/graemlins/shiner.gif" alt="" />

Waco, especially the tranny and t-case, go with your vehicle's owner operating manual recommendations. <img src="/forums/images/graemlins/cheers.gif" alt="" />

what i ment by 100% synthetic is that everything (oil and additives) is made in their factory, all other companies that claim to be full synthetic still has some petrolium in it. im friends with one of the head mechanics at a local chrysler dealership, and he said when they get a car in with the 2.7 liter (the ***** motor with the small oil galleries that always sludge up) no one wants to work on it because they dont want to clean that ***** out, but he said he noticed that people who used amsoil and penzoil synthetic had a lot cleaner motors then the others.

Playinmud, below are some excerpts from a recent article I read, please do not take any of this personally. It simply reflects my own personal opinion about motor oils and additives after very little reading on this topic:

"Part of the answer may lie in what some psychiatrists call the "psychological placebo effect." Simply put, that means that many of us hunger for that peace of mind that comes with believing we have purchased the absolute best or most protection we can possibly get.

Even better, there's that wonderfully smug feeling that comes with thinking we might be a step ahead of the pack, possessing knowledge of something just a bit better than everyone else.

Then again, perhaps it comes from an ancient, deep-seated need we all seem to have to believe in magic. There has never been any shortage of unscrupulous types ready to cash in on our willingness to believe that there's some magical mystery potion we can buy to help us lose weight, grow hair, attract the opposite sex or make our engines run longer and better. I doubt that there's a one of us who hasn't fallen for one of these at least once in our lifetimes. We just want it to be true so bad that we can't help ourselves."
"Whenever we talk about oil additives, the subject of synthetic oils inevitably crops up. Actually, the two subjects have very little to do with each other, but since many riders seem to equate additives and synthetics together in their minds, we will take a few lines just to clear the air.

Synthetic oils were originally developed for use in gas turbine engines. In most cases they are capable of maintaining their viscosity for longer periods of use and under much greater temperatures and pressures than petroleum products. Commons synthetics used for engine lubrication today are Polyalphaolefin (like Mobil 1) or Dibasic Organic Esters (like AMSOIL). They are fully compatible with conventional oils and can be mixed, providing their ratings match.

Probably the best situation is a blend of synthetics and mineral oils, such as Golden Spectro and AGIP Sint 2000. These products seem to offer the best of both worlds in protection and extended service life. They may cost considerably more than standard petroleum products, but they also can be used for much longer periods between oil changes without losing their protective capabilities.

Synthetics and synthetic blends offer a wider range of protection than standard petroleum products. However, it should be noted that this extended range of protection reaches into an area of temperatures and pressures virtually impossible to attain inside most motorcycle engines and transmissions. In other words, if you use them, you are buying a sort of "overkill protection." It's certainly not going to hurt anything -- it's just unnecessary. That is, unless it makes you feel better knowing the extra protection is on board, in which case the added expense may be well justified.

As a basic rule of thumb, using the standard engine oil recommended by your bike's manufacturer and changing it about every 3000 miles will afford you all the protection you'll ever need. But if you feel better knowing you have more protection than you need or, if you like the extended service-life feature, there's certainly nothing wrong with using a premium grade synthetic blend lubricant."

Well I did see an interesting dyno test the other Sunday on Horsepower TV and along Jim's perrenial arguement for all Jeep owners, at 6500 rpm, synthetics did produce a few more horsepower and ft/lbs. of torque so there has to be a little gain from less friction supplied by syntho but probly not at our torque end of the scale. Just thought I would throw that in to continue the argument, hee hee! <img src="/forums/images/graemlins/notooth.gif" alt="" />

Waco, I thought I was pretty good about keeping most of the Chemistry and Physics language and technical terms out of this discussion. Just plain talk. Come to your own decision about selecting a motor oil; and, buyer beware of all the hype about synthetic oil products. The main point about this discussion has been to encourage a good preventative maintenance program (regular, short term engine oil drain frequencies) for your 4x4 per the manufacturer's recommendations.

Hey Bama, did ya ever see any of them TV guys say ANYTHING bad about a product? Them guys are glorified product salesmen! They get free products to "test" and they NEVER say what MAY be on their minds..
May I add that most gains being advertised by ANY company are at or near the 6500 mark on the tachometer.
Big Jim <img src="/forums/images/graemlins/pfft.gif" alt="" />

Actually, yes I have seen one say what was actually on his mind some of the time, Stacey David, but he isn't on Trucks anymore, go figure......

Sean

This is an interesting read for those so inclined:
http://neptune.spacebears.com/cars/stories/oil-life.html

C.

I think I read every word the guy printed.. What I see is they have no "control" vehicles using regular oil..
Sure thay are testing the oil...but against what??? Without a group of control guys they are doing all that work for naught. When they finally finish they will only have test results for the 2 or 3 synthetic oils they use in the test and not any results for regular oil to compare their results to.
The guy with his hood up taking a sample in the SNOW tickled me somewhat.
Big Jim <img src="/forums/images/graemlins/pfft.gif" alt="" />