Bimmer - I wrote a post that never went through suggesting you had your answer - 0w may give better cold start protection and at least one member used it for several years with success - so go grab some 0w-30 for your next oild change. :)

To answer your most recent phrasing of the question - why would anyone not use 0w or 5w at the same price -

Bear in mind that just because today 0w-30 is readily available at comparable prices does not mean it wasn't 2-3x more in the recent past. Also bear in mind some guys on here are in other countries where the market and local laws may be very different.

​​​​​​​Many folks DO use 5w - per several posters. My Dad used nothing but Mobil 1 full syn 5w-30 for all 400k of his 94 XJ.

Why some folks don't (which is different from "wouldn't") is clear - the spec is 10w usually so folks follow the spec.
Some folks might not even consider 0w since it's availabilty has only recently been widespread and folks keep using what they always have.
Some folks like the rotella diesel oils due to the reduction in Zinc in regular oils over the years and Zinc is important to reduce wear in our flat tappet "tractor" engines that use an older design not common in newer vehicles.

Again, "don't use" is different than "wouldn't use". I haven't seen anyone say - "I refuse to use 0w-30" so if you're looking for someone to debate about refusing to use it, I haven't seen anyone available yet.

https://www.bobistheoilguy.com/motor-oil-101/

the long story, have a look at the bottom of page 2, regarding oil thickness at 75F (startup) on various oil grades

at much lower temps, the issue would be far worse

most people consider the OEM spec oil is adequate, that would be one reason why not
At the time of XJ manafacture, 0W oil was probably scarcely even available

I dont believe cost is not also a factor, there is simply no way a 0W synthetic oil is the same price as a regular 10W-30, anywhere, ever

many people also have concerns on seal leakage, and the consequences of using a much lower (1st num) viscosity oil than recommended by the maker

A decision for each person

The largest local auto transmission shop only uses synthetic or semi-synthetic trans oil in ALL vehicles

I use a semi-synthetic trans oil

I think 0W-30 or 40 is a good idea to help preserve the longevity of a motor

You guys are absolutely correct. Had it backwards. My mistake!

JX, I reverse things predictably. Wasn't till my mid 50's I discovered some Dyslexia or ADD is why everything can be backwards or I can't spell. Bimmer, Viscosity is the word, guess they check that by letting it drain through a hole, sort of like the pouring you mentioned. I gather it has to do with the length of the ploimer chains. The idea with multi grade is that sorter chains start holding hands when it warms up to make longer chains. Soon they get lazy then have a break down. Cool if you are in Michigan with kids ruining your Jeep. Me, alone here in CA my Castrol straight 30W comes with them already holding hands. It rarely freezes here, and when it's close or there I just wait a minute for this golden surip to get up into the head.( I do change it in February, then use the old for bar oil for my chainsaw) I've had no engine failure in anything for decades with that, cars, trucks, rototiller, water pump, lawn mower, generators, the wood chipper, zero piston, ring or rod failure. I haven't needed to buy or replace anything, (except the roto-tiller wheels!) Go figure why they took it off the shelf and now I need to order it. BTW, don't use it on drill bits or metal cutting blades, they won't cut well.

This Luddite is going to die with a quart of Castroil Straight 30 W in his hand, with a dozen engines humming smooth.

A low cost way to check. BITOG has been talking about this oil a lot and Project Farm on Youtube did a test on some of this (different weight not 0w-40) a while back and it's actually looking like pretty good oil. It's looking like it's probably bottled by Warren Petroleum which does a lot of Wal Mart's Super Tech branded oil.


It doesn't look like they have an 0w-30, you'll have to go with a name brand for that weight.

German Castrol 0W-40 for me.

I've used mobile 1 high mileage 5w-30 for a long time. I've never seen the need for 0w-30 even when it gets into the negative temps. It seems to have great heat resistance as well.

10W can go down to -13F
5W can go down to -22F
0W can go down to -31F

https://cimg4.ibsrv.net/gimg/www.che...9d9349ef35.jpg

I have to admit....I was a who cares as long as you have oil guy...most of my life. But there is a thread in here or somewhere(massive thread) that explains oil down to a science and compares many of the top brands...Some are good, some are great and some are amazing! After reading this, and it is a long read so have a beer or three and get your focus on,,,I was a changed person. I learned so much I was like mind-blown....That being said I feel like a schmuk because I cannot find it and I thought I even bookmarked it. :brickwall: So if anyone who reads this knows about this massive comparison thread of oils for our jeeps I hope you can share. Anyhow now I use Rotella T6 5w40 full synthetic. The top rated out of the comparisons. I currently have a mopar filter but will be switching to a wix on my next change. (Napa filter) Truck loves the oil for sure. Again I really hope someone can share a link to that thread!! My 2 cents.:thumbsup:

Would this be it? https://www.cherokeeforum.com/f2/rot...essing-188168/

THAT'S IT!!!! Yes Salad that was who wrote it!!! I knew it was somewhere! You are the man! However I don't remember that being the title at all but the contents are all there! Thanks!

From now on, I will be using 5W-30, why not.

No need for 0W or even 5W, because even if it's under -5F,
I'm not leaving the house anyway.