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how to swap to full synthetic?

Drain the old.
Put in the new.
 
Drain and pour. You will want to go to a slightly heavier grade if you are concerned about seals leaking. My personal choice is Mobil 1 because it's $5 per quart at Costco. I have also used Castrol syntech. Basically any name brand synthetic is fine.
 
I run mobil 1 15w50.

I don't suggest you run that heavy, but at 10w40 I have problems with very low pressure when my engine is working hard.
 
I use Royal Purple, felt like i gained some horsepower due to less friction, maybe just wanted to think i did, drained the old put in the new, no probs.
 
I use Elf Excellium 10W50 in my XJ, my bros ZJ my roomates RX-7. Little pricey but works great and i dont change oil for about 7-10K.
 
The anti-wear additives in lubricating oil have changed in the last few years to improve the efficiency of catalytic converters in modern engines. Mobil-1 is no longer the same as Mobil-1 of 10 years ago.

The Jeep's 4.0L pushrod motor needs a traditional mineral oil (or semi synthetic) that contains similar antiwear additives that were once available in top branded oils at the end of the 90's. I now only use 10W40 oil that is labelled 'formulated for older engines' or 'formulated for diesel engines'.
 
I run all Amsoil lubes in all my Jeeps including the 10W30 in my 185,000 mile XJ. Don't know what oil was in it up till I switched at about the 150k mark but she runs just fine. It did have a rear main leak prior to running syn that I fixed and (knock on wood) she is still leak free. (knock on wood again)
 
You ought to be able to tell how well an oil is performing by checking its color at a given mileage, no? Using straight dino oil, mine was blackish by 3000. Semi synthetics look clean to me at 4K. No grime to suggest mechanical wear or color change suggesting heat breakdown.
If semi-synth didnt have the additives or if synthetics in general didnt (synthetics being a prime part of the synth blend) have the additives to keep an older engine running smooth, then wouldnt you wind up with MORE crud in the oil and not LESS?
 
X3 on the AMSOIL i swithed on my jeep with a 163000 miles on it and it leaked for a week or soo and stopped. I use it in all my vehicles for the majorit of the lubericants too.
 
I have been running the Amsoil 15w40 Heavy Duty Diesel oil and a Amsoil filter with excellent results. I have never felt real comfortable with the "extended" oil changes though. I usually go around 5000 miles and then its time for some fresh oil. 140000+ miles and its spotless under the valve cover.

BTW, I also do a drain and fill on my transmission about every 3rd oil change or so. Its only 3-4 quarts and its cheap insurance in my opinion. I have always ran synthetic ATF in mine but some poeple swear that your transmission will fall out if you run anything than DEXIII.
 
yossarian19 said:
You ought to be able to tell how well an oil is performing by checking its color at a given mileage, no? Using straight dino oil, mine was blackish by 3000. Semi synthetics look clean to me at 4K. No grime to suggest mechanical wear or color change suggesting heat breakdown.
If semi-synth didnt have the additives or if synthetics in general didnt (synthetics being a prime part of the synth blend) have the additives to keep an older engine running smooth, then wouldnt you wind up with MORE crud in the oil and not LESS?
Click to expand...
The color of an oil is mostly a function of how much carbon gets past the rings and into your oil. The quality of the oil has little effect on this. The better oils are good at suspending the particles in the oil and carrying them to the filter, which can make an oil appear dark. Also many oils are sort of dark to begin with. Basically only a proper spectrometric analysis can tell you for sure the condition of your oil.
 
jeeperjohn said:
Drain and pour. You will want to go to a slightly heavier grade if you are concerned about seals leaking. My personal choice is Mobil 1 because it's $5 per quart at Costco. I have also used Castrol syntech. Basically any name brand synthetic is fine.
Click to expand...


Mobil One High Mileage, yes....

Mobil One Regular, No.....

The High Mileage still retains the SL certification and the correct levels of ZDDP for the 4.0l. The regular no longer does......
 
Vince said:
The anti-wear additives in lubricating oil have changed in the last few years to improve the efficiency of catalytic converters in modern engines. Mobil-1 is no longer the same as Mobil-1 of 10 years ago.

The Jeep's 4.0L pushrod motor needs a traditional mineral oil (or semi synthetic) that contains similar antiwear additives that were once available in top branded oils at the end of the 90's. I now only use 10W40 oil that is labelled 'formulated for older engines' or 'formulated for diesel engines'.
Click to expand...
Correct. Same goes for alot of the sythetics out there. The only Mobil 1 I'll use now is 15w50 extended performance formula. It still has high levels of Zn and P. But my got to is Amerilube 10w50. I'll also use any diesel 15w40 with a ci-4 rating or earlier in a pinch.
 
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