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MacKennon 10-16-2006 01:29 PM

Oil question
The owner's manual says to use 5W-30, but backyard mechanics tell me 10W-30. I prefer Mobil Synthetic over regular oil. What do you guys use and prefer for your Jeeps? Thank you!


Nick 10-16-2006 02:23 PM

Depending on what the temp range is were you live will help you determine if you should use 5w or 10w. I think the only difference between Synthetic oil and regular is the synthetic can be run for longer without changing it.

Tiburon 10-16-2006 02:44 PM

not sure if this is right.
I had learned years ago, I don't remember where, that the numbers of the oil represent the 'weight' of the oil. the higher the number the thicker the oil. I usually run 10w-30 in the summer months and 5w-30 in the winter. the first number represents the weight (viscosity) when the engine is cold. and the second number is when the engine is hot. so in the winter the lower number is a little thinner to flow a little easier.

happy Jeepin'

coolman8bc 10-16-2006 10:14 PM

I've been running 5w for both winter and summer here in MI and I've had no problems so far. I've heard synthetic increases your engine life, but once you use it once you should use it from then on.

lost 10-16-2006 10:24 PM

I am about to use(bought already) 10w30(mobil 5000)

Buster 10-16-2006 10:35 PM

It makes no sense to me why anyone would recommend using something other than what the specs call for. 10w 30 is going to be a "thicker" oil during start up. Why push the engine harder than it needs to be pushed during a critical part of its operation?? fwiw

Nick 10-16-2006 11:03 PM


Originally Posted by Buster
It makes no sense to me why anyone would recommend using something other than what the specs call for. 10w 30 is going to be a "thicker" oil during start up. Why push the engine harder than it needs to be pushed during a critical part of its operation?? fwiw

If its cold outside the 10w will become too thick and harder on the engine. A 5w will be thinner during cold temps. Thats why in my first post i told him that it would depend on how cold it gets outside where he lives.

MacKennon 10-16-2006 11:29 PM

Hey Guys, thanks for the info. I appreciate it.


import_freak 10-16-2006 11:38 PM

i use royal purple 5w30 year round

Dare2BSquare 10-17-2006 11:15 AM

Everyone seems to have their own preferences. I think that unless you are doing some extreme driving, the recommendations in the manual will not steer you wrong. The MOST important factor is making sure that the oil and filter get changed when they are supposed to. The way engines and oils are engineered now, as long as you service it regularly you should not have oil related problems during the life of your engine.

Odhinn 10-17-2006 11:51 AM

I've been running Mobile 1. 10w-30 synthetic for years and have no complaints about it. Got 300k miles (give or take a few) out of my Dodge half ton with the 318 using it. (Granted I went through 4 transmissions on that pile) As was stated by a few people above, 5W-30 and 10W-30 are the same oil weight when the oil is hot so I guess it depends on how you feel about cold weather starts and how fast you want the oil to get to the engine parts.

gcdcpakmbs 11-02-2006 03:13 PM

Mfg's recommended oil recommendation does not include "extreme conditions" as it states in the manual. If I remember correctly (which I rarely do) the manual then describes "extreme conditions" as trips less than 10-miles, stop and go driving, temperatures greater than 90 degrees F, temperatures less than 15 (I think) degrees F, or dusty conditions.

Since you are in Germany, I'd recommend you use a multivisosity with a first number of 5 to start. Startup is the hardest time on your engine, and you need the low viscosity to lube your engine as quickly as possible.

In South Texas I'll go to a 10w30 in the summer months only. The rest of the time, I'll use the recommended. On my truck in the summer I use 20w50 because the Hiway temps run 140 degrees during those months, and its over 80 degrees in the morning anyway. I also change my oil every 2k in the summer. Its extremely hot and extremely dusty.

I do like the synthetic oil, but I don't pretend to think you get longer life. I change oil and filter every 3k when normal and every 2K when extreme.

If you've got an old engine, don't just switch to synthetic. Go to a blend, and watch for leaks. Do one more blend, and if you still have no leaks, then go to synthetic. I went to synthetic on my Z-71 after 60k miles, and went from 15mpg to 17mpg. That not only pays for the oil, but I gotta believe that indicates the engine is running easier.

I'm a noob, so my comments are fodder no attention to my ramblings

Mudweiser 11-02-2006 04:55 PM

I run 10w-30 in my trucks, and in my jeep. But in my car i run full synthetic since it was brand new. In Florida its hot and humid most all of the time but i havent ever had any problems. In my old 400 small block i run straight 30 weight as it slows down leaks alot. I reckon im about as extreme on an engine as anyone could be.

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