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Giancarlo 01-12-2009 02:21 PM

engine oil?
i have a 97 tj 4.0 with 160,000 miles on it... i live in new jersey .. whats the best oil to put in big red..? high mileage, regular, synthetic?

Atthehop 01-12-2009 02:29 PM

I am in NJ and as long as you change the oil and filter on a regular basis you do not need synthetic, my yj had 200k (retired) and my tj now has 65k and I do mine every 3k.

jdhallissey 01-12-2009 03:42 PM

Mobil 1 synthetic last about 10k for normal driving. It cost 30 bucks for oil and 10 for the oil filter. I have always gone synthetic except for when I break in a new motor dyno oil only then for the first 2k miles along with oil changes at the first start up(10 mins of running) then 250 miles then 500 miles. 1000 miles, 2000 miles is when I change to synthetic.

jpdocdave 01-12-2009 04:12 PM


Originally Posted by Atthehop (Post 307118)
I am in NJ and as long as you change the oil and filter on a regular basis you do not need synthetic, my yj had 200k (retired) and my tj now has 65k and I do mine every 3k.

i agree. valvoline makes an oil called max life for higher mileage engines, thats fine to, but not mandatory. i don't like waiting 10k no matter what oil, just me. every 3k on the dot. cheap and easy insurance, its all you can do for the inside of your motor.

speepdaedeesi 01-12-2009 04:38 PM

i use a synthetic blend. i live where its really cold.. like waay below zero.. so it doesnt gel up as much when its real cold and makes for an easier start. however i dont drive 3000 miles in three months.. i drive about 1000-1500 miles a month at the most. on a bad month. so i change the oil every 3 months reguardless.. just makes me feel good inside lol.

i am a firm believe in using synthetic, even though i dont use 100 percent synth.

reson i i believe in synth is because it was created completely by humans with one thing in mind.. making it better than dino. period.

heres a good article that explains it better than i feel like doing right now

Synthetic Oil Explained

Whether it's evil stuff or good stuff depends on who you talk to. And a lot of what you hear from backyard mechanics is rumor and myth. Myth # 1 is the claim that you don't have to change Synthetic oil as often as regular motor oil. Remember when Mobil 1 said you could go 25,000 miles between oil changes with synthetic oil? Notice they haven't said that for a good number of years? Keep that thought on the back burner for now... Myth #2 is that synthetic oil causes oil leaks. In this article I'm going to try to dispell these myths for you with the cold hard facts about the differences and similarities between dino vs. synthetic oil.

Let's talk first about what "dino" oil is (Dino is short for Dinosaur, which is when it started forming). Dino oil is created from something called "Base Stock". Base stock what the oil companies get after they have processed the crude oil that comes from the ground. From there, additives are combined with the Base Stock, to create our motor oil. There are 7 main additives which include anti-foaming agents, anti-corrosion, etc, etc. At the molecular level, dino oil contains molecules of varying sizes. Imagine the floor of a gymnasium covered with basketballs, baseballs, volleyballs, and beach balls. Now imagine that all those different size "balls" are moving around, flowing past the floor. Every time a ball surface contacts the floor surface, the ball absorbs heat from the floor. That is how oil removes heat from your engine components, from surface to surface contact.

Now imagine the same gymnasium floor covered in uniformly sized golf balls. Smaller, more uniform molecules can absorb more heat from a surface, because there are more of them AND they have a larger surface to volume ratio which means they have more surface area contact. That's what synthetic oil is. A man-made "Base Stock", where all the molecules are the same size, and smaller than those in dino oil. Better heat transfer, better lubricating properties, and a lot wider temperature range without breakdown, are now obtained.

Myth #1 debunked

Oil does not break down under normal use. This is true of both dino and synth oil and is also the reason why you take oil to the Recycling Center and not the trash dump. So if oil itself doesn't ever degrade, why do we have to change it? The answer is twofold: additives and contamination. It will probably surprise you to learn that synthetic oil has all the same additives that dino oil has! The additives in oil DO break down, which is part of what necessitates oil changes. The other reason for regular oil changes is that with use, motor oil becomes contaminated (dirt, water, acids, etc). Using synthetic oil does not protect against either of these problems, which is why you CANNOT go further between oil changes when running a synthetic. You should still change your synthetic oil at the same intervals as you do with dino oil. Anyone want to guess how many claims Mobil 1 had to pay to people that were going 25,000 miles between changes?

Myth #2 debunked

Synthetic oil causing oil leaks is another commonly spread myth. The truth of the matter is that if all your engine seals and gaskets are in good condition, synthetic oil will NOT leak in your engine. The myth started because on occasion, an engine will leak with synthetic oil, but not dino oil. The reason for this is that the smaller molecules of the synthetic are able to get past very small crevices, where the larger molecules of dino oil cannot. But this does not mean that the synthetic oil has caused the leak, it simply has "discovered" an infant leak, and regardless of what oil you are running, this infant leak will eventually grow to a size that will allow dino oil to occupy and pass also. Synthetic oil has not been shown to deteriorate engine seals or gaskets. It is not some evil solvent that will break down sealant, or anything like that. Like was said earlier, it is just a man-made base stock, that is uniform and smaller in molecule size than dino oil. Nothing more, nothing less.

So if you are asking yourself "What's the point of running synthetic oil, if you can't change it less often?" Here's your answer in a nutshell.

Since synthetic oil has better heat transfer qualities than dino oil, your internal engine temperatures will be lower. Things like bearings, especially, will not operate at as high of a temperature as a result. The wider range of temperatures that synthetic oil can withstand is well suited for the air-cooled VW engine. With head temperatures normally between 300-350 degrees, synthetic will not breakdown while lubricating the valvetrain components at the heads. The better lubricating properties of synthetic in general will lead to a longer engine life as well. On average, when synthetic oil is run in an air-cooled VW engine, head temperatures stay the same, but engine oil temps reduce by anywhere from 10 to 15 degrees. This is in engines that have all the correct cooling tin in place, and are not suffering from overheating to begin with. Important note: Do not run synthetic to fix a hot running engine. Find the real reason it's running hot, and fix it!

Another benefit is that since synthetic oil is man-made, it can be tailored to suit a wider range of needs. Synthetic oil is now being made is such weights as 5w50, and 0w30, weights that are not possible to achieve with dino oils.

At Aircooled.Net we recommend that you run synthetic oils in all cases, with one exception: you should continue to run dino oil (and change it every 1k miles) if your car still has the stock oiling system.

In transmissions we can not praise synthetics enough; RUN IT, especially if you live somewhere that gets cold (under 30F/0C).

There is one thing I need to clarify though -- if you are not running an oil filter, there really is no point to using synthetic since your oil is going to become contaminated very quickly. Your engine will still benefit somewhat from it, but due to the higher cost of synthetic oil, the gain of running it before it becomes contaminated is negligible. Oil change intervals range from 1000-3000 miles in the VW engine with a strainer (not a filter). VWoM (Mexico) recommends 1k mile intervals on non-filtered engines; keep this in mind for your pride and joy! But on the flip side, the stock VW engine only takes 2.5 qts anyways, it's not going to break you if you do want to run synthetic!

Giancarlo 01-12-2009 06:09 PM

soo for my high mileage engine would running i high mileage oil or a synthetic oil be the better choice

jpdocdave 01-12-2009 06:13 PM


Originally Posted by Giancarlo (Post 307288)
soo for my high mileage engine would running i high mileage oil or a synthetic oil be the better choice

i say not synthetic. i agree about the smaller molecules and leaks starting. valvoline max life is designed to work with higher mileage seals and such. regular 10w/30 and even 10w/40 in the summer, or max life is my input.

Giancarlo 01-12-2009 06:21 PM

ok and why put 10w-40 in the summer?

jpdocdave 01-12-2009 06:26 PM

it is a little thicker, and the tolerances and clearances in your engine are worn compared to new. not a bad thing, but the thicker oil will work on a higher mileage engine, along with helping oil leaking or consumption. in the winter i'd stick with 10w30 because oil is thicker in the cold.

Jerry Bransford 01-12-2009 06:32 PM


Originally Posted by speepdaedeesi (Post 307195)
Since synthetic oil has better heat transfer qualities than dino oil, your internal engine temperatures will be lower. Things like bearings, especially, will not operate at as high of a temperature as a result.

I was fine on what you were saying until I read that, which has recently been found to be untrue. Yes, really.

WHAT? Jerry's full of it, right? And you now say you have used an IR (infrared) temperature probe and my differential housing is now cooler since you changed to synthetic? That is proof, right? Nope.

It is true if you aim an IR temperature probe to components like the pumpkin filled with synthetic lube that it will often be cooler than it was with a conventional gear lube. How can the case be cooler but the gears inside be running hotter? Simply because of this... it was recently discovered that while the synthetic lube and case may indeed be cooler when measured, it's because the synthetic gear lube is not as good at drawing heat out of the gears, etc. So the gears are running hotter but the synthetic gear lube itself is running cooler because it's not pulling the heat out of the gears as effectively as conventional gear lubes do.

You don't have to believe me on this if you don't want to, call an axle manufacturer like Currie Enterprises and ask them. In fact, they recently changed their warranty requirement that any axle built by them must only contain conventional gear lube to keep their warranty in effect. If they get a failed axle in and they determine it was filled with a synthetic gear lube, they will void the warranty because the gears run hotter with a synthetic gear lube. It was surprising to them and other axle manufacturers they talked to, and to me too.

Personally, I'm switching my axles to a conventional gear lube at the next change. :)

Jiffydarren 09-08-2009 12:51 PM

>160,000 miles

Castrol GTX High Mileage 10w30.

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