BimmerJeeper

I have about 6k on the Jeep oil (synth) so I might change it soon.
Book says 10w-30. Is there any reason to not just use 0w-30 or 5w-30 ?

Also, what rating/spec oil are we supposed to use?

XJlimitedx99

FSM calls for 10w-30 for ambient temps below 0°F and 5w-30 for above 100°F.

BimmerJeeper

Are you sure about that?

The first number, 5 or 10 in this case, is a measurement of how easily the oil pours at low temperatures. The lower the number, the thinner it will be in these conditions: a 0 pours easier than a 5, a 5 easier than a 10, etc. An oil with a lower viscosity (a lower number) will reach and protect the engine’s internal components faster.

The second number, which is 30 for both of these oils, indicates the thickness of the oil once it reaches operating/high temperatures. A high viscosity (thicker) oil will adhere to mechanical components better when subjected to high pressure and stress and can withstand higher temperatures before thinning out beyond its working viscosity (past which it can no longer provide adequate protection).

jpz

My Jeep has had 5w30 in it since brand new. Never had an issue.

00t444e

15w40 here no issues, and has better oil pressure than it did with 10w30.

Ralph77

I think you have that backwards.
In my '01 XJ FSM it says:
0 degrees F to over 100 degrees F 10W-30 (Preferred)
32 degrees F to below-20 degrees F 5W-30
Since I drive so little I change my oil twice a year.
In Apirl, 10W-30, and October, 5W-30.

Morat

For my expected temp ranges the FSM recommends 10w30. I would use 0w30 except there's a brand over here (Comma) that does a reasonably priced fully synth 5w30 with 1200ppm Zinc so I use that instead.
To my mind, as long as the higher number is correct , the lower number affects cold start protection where lower is better.

awg

there is a well written article floating around on the Internet...can be found under "oil viscosity 101 bob is the oil guy "

it concludes you should buy the lowest viscosity (1st figure) oil you can afford

as basically most wear is at startup, it concludes only synthetic 0 weight is good enough to prevent this entirely (read it)

for the upper viscosity it says use the factory rating, (or one rating higher in a hot climate or worn engine)

I believe the FSM calls for 10w-30.

I use 10w-40.

0-30 and 0-40 are about 3 X the price

BimmerJeeper

0-30 and 0-40 are about 3 X the price


0W-20 is $20



5W-20 is $20



5W-30 is $19



10W-30 is $20



0W-40 is $25

s346k

Suprmn

Lots of good answers here, but I will add this. The manufacturer spends a ton of money on R&D and provides an oil viscosity vs. temp chart in the owners manual. The only time I choose something other than what is recommended is in severe circumstances like when I was in Alaska. Other than that, want to do your jeep a favor? Change the oil and change it regularly with good quality filters. Going from 10W or 5W to 0W will likely not provide any benefit that any of us will actually ever witness.

PatHenry

This is true for folks in the U.S. It may not be the same for folks in other countries.

PatHenry

I agree. The Jeep I6 is a durable and reliable engine that easily goes 300k+ miles with normal maintenance - any benefit between the grades is certainly grossly overwhelmed by the benefits of properly changing the oil.

awg

You did not include the lowest prices of 10-30W oil on Amazon, for comparison, which I imagine to be at least half the price of those you did display, so lacking scientific rigor !

In answer to your question, imo, there is a good reason to use 0W oil, that are fully detailed in the article I mentioned (startup wear)

Cost is the only reason why not. This "may" partially offset by longer oil change periods

BimmerJeeper

The point is that 0W is nowhere close to double or triple the price.
It's all basically the same price. So, the question remains, why does anyone NOT use 0W or 5W
when they are all the same price ?