Too late for synthetic?

I just picked up a 1996 XJ Country Edition with a little less than 64,000 miles on it. The only place it leaks seems to be from the oil filter adaptor o-rings. Should be a simple and easy fix.

Anyway I have been thinking of running synthetic in this 4.0L. I've also heard horror stories about people who start using it in engines with higher miles, and new leaks start to appear.

Should I go synthetic, or just stick with conventional? What if I were to introduce synthetic to the engine as a blend? Start off with 2 quarts synthetic and 4 quarts of conventional. On the next oil change, do 4 quarts synthetic, 2 quarts conventional, and then on the 3rd oil change, run full synthetic.

Does this sound like a good idea, or just a waste of time?

If I do go with synthetic, would you guys recommend Mobil 1, or Amsoil? I have noticed if you take a bottle of Mobil 1 and a bottle of Amsoil, both of the same weight, the Amsoil will pour out faster.

I picked up a 100K miles 97 and put Mobil 1 into it. Yeah I did rear main, but the rear main needed replacemnt anyways. So go ahead and do it but at worst case be ready to do the rear main should it get "ungunked". Anyways the engine seems to run smoother with Mobil 1 so it was definately worth it.

do a engine flush 1st..then run you syn. oil..after 3000 miles change again..go for another syn and filter than you should be ok for 5000...||charles||

It's never too late! Just be sure you use a good engine flush before you add the syn-oil. Not that I'm biased, but I just put 7qts of AMSOIL 10-40 and a Amsoil filter in my XJ I6 with 245,000miles on it. Engine runs much smoother and QUIETER than before and I wont need another oil change for 25,000miles!
@ 12,500mi I need to change the filter and add one qt. That's it!

I sell Amsoil, but Mobil-1 is good stuff too. Check it out:
http://www.lubedealer.com/tycoon

Give me a snail mail address and I'll send you more info. on the special line of 4x4 lubes. Oil, Diff fluid, Trans fluid, and waterproof grease.

90Pioneer said:

I just picked up a 1996 XJ Country Edition with a little less than 64,000 miles on it. The only place it leaks seems to be from the oil filter adaptor o-rings. Should be a simple and easy fix.

Anyway I have been thinking of running synthetic in this 4.0L. I've also heard horror stories about people who start using it in engines with higher miles, and new leaks start to appear.

Should I go synthetic, or just stick with conventional? What if I were to introduce synthetic to the engine as a blend? Start off with 2 quarts synthetic and 4 quarts of conventional. On the next oil change, do 4 quarts synthetic, 2 quarts conventional, and then on the 3rd oil change, run full synthetic.

Does this sound like a good idea, or just a waste of time?

Click to expand...

You must have read one of my previous posts and gotten my idea. Yeah, go ahead and do it. At 64k miles, your engine is still young by 4.0 standards so the chances of any leaks from PITA areas like the rear main seal or valve cover gasket are low.

When I changed over to synthetic in my 88 XJ i had 133,000 miles on the engine. Before I changed the type of oil I had replaced the oil filter mount O-rings, valve cover gasket, and oil pan gasket. The only oil gaskets I had not changed was the timing cover stuff and the rear main seal. From reading on here I had figured I had new gaskets in all the locations people post about leaks.

I just did a switch over to synthetic, none of the phase in stuff. Just put in 6 quarts of synthetic. I did change the oil filter at 1000 miles just in case some crud had been broken loose. I will say my XJ did not get used much but in 2000 I put 15,000 miles on it in 4 months. I was moving to a new town 450 miles away and made trips on the weekends. I had been doing 3,000 oil changes at the local jiffy-lube since I was so busy. So my engine was clean on the inside from the 7 hour one-way runs. It was up to temperature so I had no problems with the switch. I pulled the oil pan before I went to synthetic to see if anything was in the pan. It was totally clean, the whole engine was clean. Changing your oil on a regular basis is key, synthetic just has better properties than conventional oil.

The US Military has been using synthetic oil for decades, you know they would not switch unless it had better properties. Also, I use Mobil 1 oil. I use it because I travel 400-600 miles from home to Missouri and Chicago. I figured if I am down a quart I can find Mobil 1 about anywhere I go. I hear Amsoil is good stuff but the lack of availabilty in stores is it's downside. You have to decide if you drive locally and you will always be close to your stash of amsoil. As with any oil a good filter, you have to decide. I have tried different brands and take note on my oil pressure at start up & idle at stop lights. Use the filter which gives you the best oil pressure. There a web site out there where a guy cut apart filters and his conclusion was "anything but the orange Fram". Do a google search on "oil filter study" and you will find his results.

I changed my '88 to synthetic at 175,000 miles. I had previously done the rear main seal. No new leaks, and the rear main seal eventually needs to be replaced anyway so I would not use that as a reason not to switch.

I switched mine over to Valvoline's Max Life Synthetic, its new. It has the benefits of an oil made for high mileage engines and its also 100% synthetic. Oh by the way I switched my 90 XJ over to it at 119,000.

I switched to Royal Purple synthetic on my '96, but only have 38K miles on the original 4.0. After 4K miles on the RP, it still looks clean like it was when I poured it in. Engine runs really smooth, even at high RPM's. No leaks whatsoever. It's about $6 a quart though.

I am running the Valvoline MaxLife synthetic, so far so good, my jeep doesnt leave puddles anywhere so I consider myself lucky, its been a year and no new leaks. I just swapped it out like any other oil change, no problems so far ;-)