Synthetic oils

[joedurt1]

1998 XJ with 85000 miles.
I am thinking about putting in synthetic oil on the next change. Is there any issues associated with doing that change over. I've heard that it needs to be flushed first and also have heard that it is not true.
Thanks,

Durt

 

[Sparkman]

It depends. If you plan on changing your oil frequently (3-5k miles) you should be able to switch to synthetic without doing anything. If you plan on running extended drains you should use a good cleaner first. The reason for this is the synthetic is a good cleaner itself, so it will get dirty quickly in an engine that has seen conventional oil for that long. When I switched my '01 to synthetic I ran www.auto-rx.com through it first.

 

[XJ_ranger]

right, the first time you put synthetic in, it will clean out your engine of all that it in it currently (and could cause you to have leaks that you didnt before, because something used to be blocking them) (this was my expierence)

thus i reccomend that should you decide to go for snythetic, change it after 300 miles, or flush it first. after that you can go like 7.5K miles before servicing (even in aggressive off road stuff) because all the molecuels start out at exactly the same size, they all break down at exactly the same rate, (as opposed to organic oil that starts out with different sized molecuels and some deteriorate fast, and then cause the otherones to break down fast as the oil gets thinner the breaking down occurs faster)

and synthetic is more expensive...

just a few things to think about
:attom: :attom: :attom: :attom: :attom:

 

[minus one]

hm.. i've always heard that you don't want to switch on higher milage vehicles just because of the possibility of new leaks.

anyone made the switch and found this to be true? my father-in-law swears by synth's but i'm still a little leary.

thanks!!

 

[junkxj]

I decided to switch my girlfriends oil to synthetic at about 140k in her 5.2. It made it start burning oil and smoking almost instantly. If your motor is not in good conditon, stay away from synthetic.

 

[Dr. Dyno]

On older engines synthetic oil will remove gum, varnish, and other deposits from inside the engine and may cause old seals and gaskets to leak. Those removed deposits could reach the oil pump pickup screen, clog it up, and cause the oil pressure to drop.
You could get around that problem by introducing synthetic oil in stages e.g. 1st oil change use dino 4 liters/synth 2 liters, 2nd oil change dino 2 liters/synth 4 liters, 3rd oil change full synth.

 

[timjeep]

but is one synthtic oil better than the rest or are they all the same. just thought someone could answer that question.

 

[RichP]

They are pretty much similar, I prefer Mobil-1, use Castrol Syntec in my Yamaha because the Mobil-1 is too slippery for the wet clutch in the bike, M-1 in everything else.
As for changing it, just change it, I did both our TJ's last winter when we got them, both had over 85,000mi ea, changed all the fluids and that was that, no leaks, no extra burning, no problem. Keep an eye on your dipstick, once you can't read the hash marks thru the oil change the filter and add a quart. The syn's are high deteregent so they will clean out any sludge you have in there, not real fast like a flush does but more slowly, thats why you watch the dispstick for color.
Your next question might be about a syn.dino blend, make your own, nowhere on the blend can does it say 50/50 and if you do the math that proves it, the mixes are an advertising gimmick

 

[MonkeyGrass]

I personally love the Shell Rotella T 5w-40 syn. I run it in every vehicle I own (XJ w/145k, Civic w/85k, Del Sol w/129k, and a Suzi 750 V-Twin with 26k). I started out with it just in my bike, because I had read it was great for wet clutches... It is. No slippage in a bike (and I do like to wring its neck from time to time! ) and my engines have always been rock solid in all 3 of my cars. I love the stuff. Once you get that first change out of the way (I did mine at 1500 on each vehicle to get any sludge out. There really wasn't that much, really) - I'm getting 5k, sometimes 7500k, depends on the conditions. If I'm doing a 10 hr drive to S. Florida, then I'll change it early at around 5. If it's just standard driving, I can let it go to 7500, and even then I change it because I feel guilty, not because the oil looks or feels broken down. People who say that syn is a waste of money don't realize that you can double your mileage between changes, once you have the interior of the engine clean and running well, and even when you figure a couple bucks more for the oil, it's not twice as expensive and I feel like I end up saving money in the long run.

BTW - sounds cheesy, but WalMart carries the Rotella T Syn (Dark Blue bottle) for $12 a gallon. Yes, that's $12 A GALLON - 4 QUARTS. That's the price of a good Castrol or similar conventional oil in most stores. I'll spend $3/qt on high quality syn anyday. Add in the double-mileage factor, and I feel really good about using a very high quality syn at half the cost of dino oil.

But again... as I saw in another thread:

Coke or Pepsi?
Regular or Decaf?
Less Filling or Tastes Great?

The world may never know....

I know what I use and I love it. Everyone has their own reasons and preferred brands. What I do know is that syn has beat conventional oil in every test known to the industry, and if cost is your main objection, then I think I've demostrated the cost-effectiveness I get from syn in my post!

Good luck, and let us know what you decide to do.

 

[minus one]

hey junkxj... after you switched it all over and started leaking, we you basically screwed and had to go in and make sure everything was sealed up again? i'm sure it wasn't as easy as just switching back over to standard oil.

so far, i think i'll just stay where i am...

 

[jp_of_fire]

I received my XJ with 207,000 on the odometer. the original engine threw a rod with 90K on it. So I actually had a motor with 117,000 on it. i figured i would go to synthetic. In my case, that was a mistake. I started leaking severely from the rear main seal, a Class II leak at that. I switched back to conventional at the next change and no more leaks. I also noticed a huge difference in oil pressure. The syn oil ran a lot lower oil pressure, especially after the motor ran for a long period of time. The Castrol conventional i use now only drops a bit on the gauge after the same amount of driving. I concluded syn oil was not for my motor. Also I was told that SYn trans fluid is bad for the AW4? Something to do with the syn being too thin? I did use syn in my front and rear diffs as well as my t-case with no problems.

 

[XJCasper]

At what milage is it too late. I have heard enthusiasts of every type of vehicle I have owned say the same thing about high milage. So when is too late to go to synthetic. I might be buying a 1996 XJ tomorrow with 66,000 miles. Should I go Dyno or Synthetic?

Thanks
Jason

 

[Kejtar]

At what milage is it too late. I have heard enthusiasts of every type of vehicle I have owned say the same thing about high milage. So when is too late to go to synthetic. I might be buying a 1996 XJ tomorrow with 66,000 miles. Should I go Dyno or Synthetic?

Thanks
Jason

I just poured synth into the 97 I got and it had over 100K on the clock. I did do a rear main on it though but it had a leak there before I poured the synthetic into it. My 98 has been running on synth for a while now and just before I rolled it @ 150K or so I was considering doing rear main cause it started to leak..... Btw, the synth will not make it leak, but it will make any existing leaks look like they're leaking more cause it will clean out the crud that might be clogging the leaks.