Synthetic oil for '95 Jeep Wrangler

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Nov 17, 2002
Hello, everyone!

Just purchased a '95 Jeep Wrangler 4-cyl. with 128,500 on it. Though I'm a huge Jeep buff, it's hard for me to imagine someone (salesman?) using it for serious highway cruising; but, oh well . . .

Anyway, the oil pressure seems to be holding just fine on it. And since I'm going to be beefing it up in the suspension and performance departments for some serious off-roading, I"d like to switch it over to synthetic. I'm just assuming it's been running on dead dinosaurs up to this point.

Is it advisable to do an engine flush, or just simply make the plunge with the synthetics?

Any other advice, tips, etc., are very much welcomed.

I would recommend running a 500 mile interval with Schaeffer's Neutra or Auto-rx as a cleanser before going to synthetic, just to be safe.

Although if you wish, you can switch over without those things, just keep the first interval at a conservative 3000 miles, then after that on the next interval you can go longer.

There has been a lot of discussion on this topic so if you do a search you will find lots of info.
I like a synthetic 10W-30 or a synthetic or non-syn 15W-40. Your 2.5 fourbanger was the basis for the 4.0 inline 6. Good, solid motor, but is a bit of a wheezer. Free up the intake and exhaust and you will get a noticable increase in power. Good luck.
My 2000 TJ also has the 2.5L Great little motor in terms of durability but it is anemic most of the time. Mine is lifted 4" and running 32" tires with both ends locked. I added a K@N cone filter setup and a highflow muffler and swapped in a 4.0 throttle body and noticed very improved performance for about $200 bucks. I also am running 4.88 gear ratio which is what really helps push the larger tires. I'm running M1 Supersyn 10W-30 and it really seems to like it. No oil consumption at all in 5K intervals. I would go the route Patman suggested with Auto Rx or Neutra and stay away from the GUNK type engine flushes. After that go with a 10W-30 synthetic.
hey im running the 4.0/AX-15/4.10/33's combo and it pulls sweet! Just gotta rub in the 6 cylinder factor!!
But i wouldnt swap over to synthetic with those miles in any jeep engine. The seals probrably are built up and that is keeping the leaks away. Keep using a good dino or even max-life type oil but ive seen first hand 5 jeeps swap to synthetic and start leaking after they had no leakage in the past (these were all within 3 months of a swap). Im a jeep nut and I would advice a trip over to or and search through past posts and you will find leakage issues.
Picking on us little 4 banger Jeepers! If I could do it over I would have gone the 4.0 route but I'm now committed to my TJ so i've learned to live with a little less power. There is also another upside to the 4 banger, it makes it alot harder to break things offroad with the little amount of torque it throws out.
For those of you with higher mileage who are afraid to go synthetic, what about the Schaeffer blend? It performs like a fully synthetic oil, but because it's base oil has less PAOs than a full synthetic, it should not cause a problem with older seals.
Thanks for all the replies.

Several months ago, I sold my '92 Jeep Cherokee 4.0L that had around 105,000 miles. It was purchased used several years prior with approximately 50,000 miles. Not knowing any better at the time, I had switched it to Mobile1 synthetic. No engine flush was used; just switched cold turkey. I never had any leakage issues with that terrific engine. So, I still plan to run syn in the '95 Wrangler's 4 banger, especially since I just purchased a few bottles of Auto-Rx.

Yeah, the 2.5L doesn't have that much power, but with a few performance tweaks, it'll be fine. Besides, the majority of its miles with me will be around town. Don't worry fellow Jeep fans, for I'm definitely going to take it off-road as much as possible. At this point, I'm leaning towards a 4" lift (Rubicon Express or Rusty's) with 32 or 33" tires. Does the stocker run 4.11s?

higney85: Thanks for the links. I'm always looking for good Jeep and/or Subaru links.
UberWRX: 5 speed - 4.10
Auto - 3.73

I'm currently running Rusty's lift kit and it's a very good starter lift kit. However, it does not come with things like new adj control arms and adj front track bar and quick swaybar disconnects like the RE kits do. If your on a budget Rusty's kit for what it costs is hard to beat. 33's is very doable and great around town with stock gears but it will be a dog on the highway. Before I regeared I was gettin passed by 18 wheelers up steep grades like I was standing still!

Thanks for the gear info. Haven't picked up my Haynes manual yet.

I'm in Marietta, OH, so I believe you're about 100 miles away. Perhaps we could get together for some 4-wheelin' goodness sometime; once I get some goodies on the YJ, of course.

I'd sure hate to be passed by semis. So, if I go with the 32s or 33s, I'll put in 4.56 or 4.88 ring/pinion.
I don't know how I could have any less power in my ZJ. I'mrunning 30’s with the standard 3.73 gear. I really wish I had another 50 lbs torque and 25 more ponys.
UberWRX: I'm up for it. There are many places to wheel in a hundred mile area around us. I try to get out about every weekend. Oh, please go with the 4.88's if you ever decide to regear your YJ as the 4.56's don't give you the gain you would expect for the money to regear.
yes your YJ has 4.11 gears stock but you will lose your 5th gear RPM's on the HWY. I went from 3.07 to 4.10 and that was a major difference. I went on and put a detroit up front and left the rear open b/c the D35 is a weak POS. Look into the 8.8 swaps- thats what im doing. Also i wouldnt drop down to 4.88 b/c the D30 will hold more then you think (max of about 35's) but the pinion is really small on a 4.88. 4.56 would be as low as id say to go and that should do well for 33's. Just thought id fill ya in. I know very

Originally posted by higney85:
the D35 is a weak POS.


Yeah, my Jeep Cherokee had the c-clipped D35 in the rear, and I was always afraid it was going to break at any minute while I was off-roading. Surprisingly, it held up just fine.

highney85: Could you recommend a good place to purchase the 8.8 rear axle?

Ryan00TJ: We'll definitely get together one of these days.
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