Synthetic or Regular oil question
 

Hey guys!

In the past, i have ALWAYS switched to synthetic oil with a new vehicle. (6+ vehicles). With my new jeep cherokee (a 98 with 109k miles, 4.0l) the dealer I bought it from made mention to keep it standard oil and not to go synthetic, that it may 'sludge' or even cause damage to the exhaust system due to being a thinner oil, or something like this. He also thought it may cause it to leak oil in the seals.

Is any of this true? I had always been under the impression switching to synthetic was expensive, but better for the car and improved performance and mileage slightly, as well as needing to be changed less frequently.

Thanks for anyone's time in answering!

synthetics can make a small leak more noticeable due to the viscosity and smaller molecules. but if you dont have leaks then no worries. i dont think it would effect the exhaust in any way... just my thoughts .

EDIT: and no it wont sludge. it should be less likely to sludge.

I'm like you, in that when I get a new vehicle, the first thing I do is research what oil reputable owners seems to recommend. For my XJ, what I found was Rotella T 15w-40. I found some people who said they used Rotella T 15w-40 in warmer weather, and switched to Rotella 5w-30 synthetic (T6 I think?) in the cold weather. I have run the 15w-40 year round in Maryland and I love it. Just my .02 to possibly save you some time.

Get the facts as a oil myth or 2 have already started in this oil thread.

https://www.google.com/#hl=en&gs_rn=...w=1280&bih=584

http://www.supramania.com/aehaas/

The 4.0 engine has been designed for the 10W-30. there is a lot of sence and non-sence around the topic of switching to synthetic oils or not, just try a search on this, it will give you the info. depending on the weather (subzero etc) you could consider a light oil in cold weather. However, if it runs fine on the 10-30, just stick with what the engineers have come up with as being the best for your vehicle. Yes, synth will require less frequen change, but for a sturdy engine like this and not being a fine tuned racing ride, the more frequent refresh with regular isnt bad. Synth will not improve mileage. Save yourself the confusion, stick with the recommended oil which is fine.

The dealer is a moron. Synth does no harm, in fact is less likely to sludge up. It can under certain circumstances leak from places dino oil does not, but that's because there is a fault in the seal the smaller synth molecules can slip past, not a fault with the oil.
If you like it, run it.

I don't see an advantage in mine because I'd change it at 3-5K anyway, High mileage motor, short trips, prone to fuel and moisture contamination. I can't see draining and tossing synth on that short of a schedule, it's just too costly. But there is certainly no harm in running it if you want to.

Now...new Jeep? Where's the pics?

My thoughts exactly.

My old jeep was wrecked (the one i painted flat black as a project off roader car). My new jeep is green, much better condition in both body (surprisingly no rust) and half the mileage. I'll get a thread going with the old jeep wrecked and the new one with pics soon as i get them uploaded.

as for the oil, thank you for the posts. i am considering all your input, currently leaning toward keeping it dino oil this time, doesnt seem like there's any advantages to synth in a jeep. was just hoping i'd get better performance, mileage, and all around better for the engine. may not be the case with these vehicles. thanks again!

Just to clarify, the 4.0 wasn't necessarily designed for 10W-30. The factory service manual recommends different oils for different temperatures, however it states that the grade should always be 30 or 40. The initial value (5w, 10w) is often dependant on climate, up here in Canada many recommend a 5W for the winter, users in Arizona might prefer 15w-40 all year round.

Although I will agree with you in that 10W-30 is probably a good choice in general for the average Jeeper.

Your dealer is an idiot. Run whichever oil makes your Jeep happiest - they do fine on synthetics. 0W30 through 15W40, keep it low if it's cold. Just don't run a cheap filter lol

djb383's link is good reading... maybe send it to your dealer LOL

I'm a big fan of Valvoline MaxLife 10w40 in my climate. After reading reviews about it, it is pretty legit stuff.

Correct, I should rephrase here: the engineers who designed the 4.0 have thought 10w-30 to be the engine oil of choice for normal temp range. Sure don't want to add to the confusion here hehe.

Even though it will never ever freeze here in Brisbane, Australie, thats what I run (where I could go 15 W-40 or even 20W-50) with our ambient temps). It runs fine and smooth.

I use Mobil 1 10W-30 in both my Jeeps.

Change interval 6-8,000 miles.

My '87 Renix has 220K original engine miles. It likes the Mobil 1 over conventional oils. No leaks.

I own a 95 jeep cherokee XJ just turned 164XXX miles.
I'm using Mobil 1 10w30 High mileage about $15-$16 a 5gal Jug. and 1 add. quart. With Lucas oil stabilizer.
Always trust Lucas, before crappy mystery oil. Lucas has saved me motors time and time again.

Follow the repair manual guidelines.

Why are you using Lucas and why do you think it's solving what problems?