Go ahead and try it. If you too scared to put it in then just go with regular Oil.

What type of Engine do you have?

 

Synthetics have smaller molecules than dino oil plus have cleaning agents in them, better than dino. What happened is the seals got cleaned and then leaked. You put dino back in it.. and it sealed it up again. Best thing is to switch to synthetic on a new engine with good seals... and the oil will keep them in good shape.

Swap it over... if it leaks... go back. No harm done... well unless you let it leak alot

If you have the HEMI... you must put synthetic oil in it for the MDS to work properly.

 

You don't need synthetic in the Hemi to work properly, but IMO it does make it work better. Both my Hemi rides have 5W-20 synthetic in them.

 

:metoo:Exactly. You do not need synthetic oil in the 5.7L HEMI, but you do need 5W-20 viscosity lube oil.

Mine also runs better on full synthetic (butt dyno method).

[You can try a synthetic blend first to see if there are any adverse indicators.]

 

Meh why cut to the chase if it runs better and is better over all (longer changing periods) why not use test tube oil? lol

 

It is better to switch over to synthetic when the engine is newer and has less wear (50-60k) or less, but go ahead and check your jeep to see if it has any oil leaks,if it doesn't than switch to synthetic and keep an eye on the oil level, you wont hurt the engine and if any leaks do appear you can either have the seals/gaskets replaced or switch back to dino oil and the leaks will seal themselves up.

My old 99 WJ with 180k v8 slightly burned and leaked oil with dino so I did not even attempt to put synthetic in it because it would've probably cause more leaks.

I went ahead and switched my 09 WK v6 with 6k miles over to synthetic so I know I wont have any problems doing it in the future. I did notice a slight increase in performance and a 1/2 mpg increase.

 

Lol I know my old 04' WJ 4.0L had about 170k before I switched to Synthetic. I ran it until 185k and sent it to the middle east! I had no problems after I switched. no Leaks, nothing. It ran a bit better.

 

Yeah but my old 99 WJs drive-train wasn't exactly in best condition and the engine wasn't maintained very well, it has so much sludge build up it was unreal(don't buy from friends) that's why I got rid of it and bought my 09.
I wanted to get a head start on switching my 09 WK to synthetic since the motor is new, every little thing helps this small V6.lol

 

Ok, my "05 has 54K and I started putting synthetic in about 6 months ago and don't think I have any leak but I'm I just throwing out money through the window or just keep it regular. I change at every 3K miles.

 

Your throwing money out if your switched to synthetic and are still changing it at 3k miles, synthetic can be changed at 6k miles or a little beyond because it has additives that last longer than regular oil. Change it a 6k miles and you'll be fine and save some money.:thumbsup:

 

I changed over the synthetic at about 130K. Just check your oil level just in case you have a oil leak. If you do have a oil leak, switch it back to the normal stuff.

 

i switched at 60k miles and it didnt leak a drop. it runs much smoother now.

 

Have 88,300 on mine thinking about going syntetic but I change my oil every 3500 miles. Is synthetic better in the winter? I also noticed dealer uses 5w20 now instead of 5w30? Is this better to use in the winter?

 

I know this is a bit of an 'apples to tea kettles' comparison, but I bought a 96 240SX with 135k miles on it, switched to synthetic at 145k miles, sprung a front crank seal nearly immediately, replaced the seal, ran the odometer up to 272k miles on synthetic then sold it. For me, changing a $4.00 seal was well worth the bit of 'extra insurance' that came with using synthetic.

 

i plan to change to syn as a test of my engine for leaks and if it dont ,,i will still only use a blended oil,,,mine has 170000,,5.9

 

what about changing "from" Synthetic Oil to High Mileage Engine Oil
This fella at Jiffy Lubetoday talked us into changing, we had a 3 hour drive after the oil change. about 70 miles into the drive the engine started knocking really bad

we made it home, but now I don't know what to do ? Make them fix it, or is that reasonable?

Any and all suggestions are welcome

1998 Jeep Grand Cherokee 253,000+ miles (4.0 6 Cylinder)

 

First mistake was Jiffy Lube. Don't your local dealers have express lanes at the same price points?

You MAY be able to recover something from Jiffy Lube, where a lawyer in your area familiar with vehicle service issues would be worth a few bucks for a consultation.

There are high mileage synthetic blends... frankly think they are marketing wallet drains. I had more than that miles on the same engine and just ran a wide viscosity Castrol synth until the local dealers started the express lanes, and they used Pennzoil.

 

First, you're in the wrong forum. This is the later model Jeep forum. Second, check the oil level and make sure it is full. Third, look for oil leaks, as sometimes switching to synthetic at high miles will cause leaks. Good luck, and watch out for the mosquitos this summer up in Kenai.

 

"from"

Synthetic Oil to High Mileage Engine Oil


oil was still full after 70 miles climbing the mountains and I just checked it again and it is still full

 

I'd go back to synthetic if you weren't having any problems. Kind of, if it ain't broke, don't fix it kind of thing. With that many miles you may have to go to a little heavier oil at some point, at least in the spring summer months. In the cold winters, a little thinner oil. Are you using a multi-weight oil (i.e. 10W-30) or a single weight oil, such as 30W or 40W?

 

Thanks for your time and replying so quick
Also sorry, I should have looked 'where' I was posting, I just followed the
"Re: Switching to Synthetic Oil in High Mileage Engine" thread


Looking on the invoice from Jiffy Lube they put in "Pennzoil Hi Mileage 5W30"

This knocking is awful, I just started it up and the knocking starts right away, engine doesn't even have to warm up first

 

I would think that at 253K+ miles you'd probably be needing a heavier oil. What weight oil were you running with the synthetic? 5W30 seems a little light to me. Can you tell where the knock is coming from? As soon as it starts, is it a real deep tone knock, or is it a higher pitched knock? Can you tell if the knock is at engine RPM (probably lower end), or half engine RPM (probably top end)? Deep, low pitch knocks are usually main bearing (deepest tone) or maybe a rod bearing (a little higher pitch), piston noise is more like a rattle than a knock, and top end (lifters/rocker arms) are usually a higher pitch, mostly like a clicking sound rather than an out and out knock. With that many miles, I'd probably put my money on main/rod bearings, as a good synthetic will normally prolong engine life and keep the top end in good shape. The bottom end takes the most beating, especially if you repeatedly put a lot of load on the engine.....mountain climbing, towing, lots of WOT use, etc. It could also be that it is near time to give some serious consideration to major engine work, if you want to keep the vehicle. Without hearing the noise, it's hard to figure out, but for starters, if they've put in a lighter weight oil, I'd switch to a heavier oil and see what happens. At best, this would just cover up a problem that is probably already there. Good luck and let us know what you find out.

 

until now I was using Mobil-1-10W-30, it does seem to be a "higher pitched knock", we usually do the oil changes ourselves (i could kick myself) for taking it to Jiffy Lube! I have read some of their reviews and I don't see a lot of good stories.
We are going to change the oil today and put Mobil-1-10W-30 w/ Fram Ultra Synthetic Oil Filter and will let you know how it turns out
I was talking with another jeep owner today and he suggested putting in "Lucas oil treatment" what are your thoughts on that?

Thanks again for all replies

 

If you can find the Castrol 20-50 or 10-40 from anyone that should help.
I used STP Oil Treatment.....

Is it a lifter making noise, or something in the bottom end?

Lifters can often be quieted down by a Seafoam treatment, but then you'd want to change oil afterwards if you put it in the crank case.

 

If you've been running synthetic forever, the innards of the engine are probably looking really good. It is possible that the dino. oil has gummed something up and, if it's a fairly high pitched knock, it could be something like a lifter. I'd start with your oil change and see what happens after a few hundred miles. Personally, I am not a big believer in all the different additives as, if you've always taken good care of it, especially timely servicing, you shouldn't really have too many issues. I guess additives have their place on poorly cared for vehicles.....I just don't use them in any of my vehicles. Just my 2 cents.

 

ok! put Mobil-1-Synthetic-10W-30 w/ Fram Ultra Synthetic Oil Filter
let it run for about 10 minutes, it does sound a 'little quieter'
but will take it for a ride tomorrow, the noise started about 70 miles down the road so ~ i think i will take it 70 miles and just test that out, will come back with a report then

 

Well took it for a ride ... less than a mile down the road, the whole jeep started shaking, lost power, noise got really bad, it all happened so quick I am just in tears! I managed to start it back up and crawl home, it didn't have much power (pushing on the gas) then halfway back home it gained some power ? ! ? ! I don't understand it!

 

Like I said in my Post No. 23, with 253+K miles, it may be time to start thinking about some major engine work if you plan to keep the vehicle. For sure it's time to have someone that is knowledgeable have a look at it and see if they can determine where the problem(s) is/are, and if it is possible to "save" the engine for a little longer. The 4.0 engines were pretty rugged units, but they are not immune to problems at high mileage. Good luck and let us know how it goes.