Senior Member
Quote:
Originally Posted by drhoward1988
Walmart brand deisel oil, dello by chevron, mobil 1, shell Rotella series, all good oils.
^^^x2^^^ All five brands are about equal so I shop by price. Walmart SuperTech 15-40 diesel oil is a bargain....and very good oil!
Quote:
lolOriginally Posted by mschi772
You need Oil Jesus.
Quote:
My lawnmowers too, lolOriginally Posted by dcollins3208
I use T6 5w40 in almost everything I own. Wally world has it on the cheap. T5 10w30 will be just fine for your rig
Quote:
Synthetic oil is NOT thinner. For example: 5w30 dino and 5w30 synthetic are the same viscosity. 10w40 dino and 10w40 synthetic are the same viscosity.
Moving on to what multi-viscosity ratings actually mean...
5w40 means that when COLD (0 deg C) its viscosity is that of a COLD 5 weight. When HOT (100 deg C) its viscosity is that of a HOT 40 weight.
Thicker is not inherently better. Long, technical story short, where oil viscosity is XwYY, X should be as low as possible. Even a cold 5 weight is still much thicker than a hot 40, so some people's belief that 0w__ and 5w__ oils are too thin for the 4.0 is false. YY can be 30 or 40, but 40 has been proven to not be inherently any better for the 4.0 than 30.
Now, you think that gear oil is thicker than motor oil because gear oil has ratings like 80w90. Gear oil isn't actually that much thicker. The ratings are so much different though because they are rated in a completely different way for different temps/circumstances. Regardless, you should NEVER use gear oil in the engine.
By running 15w40, your oil is needlessly thick when cold which could be producing increase wear during warm-up. Once it's hot, it's a 40 weight, and that is OK, but ultimately unnecessary. A 30 will protect just as well or perhaps even better and could provide a slight MPG boost.
Quoting myself from a thread on a different forum:
Thanks for this. Could you provide a link for the scientific studies about UOA's and the 4.0? I'm not sure where to find that kind of info.Originally Posted by mschi772
The misconceptions! You need oil Jesus.Synthetic oil is NOT thinner. For example: 5w30 dino and 5w30 synthetic are the same viscosity. 10w40 dino and 10w40 synthetic are the same viscosity.
Moving on to what multi-viscosity ratings actually mean...
5w40 means that when COLD (0 deg C) its viscosity is that of a COLD 5 weight. When HOT (100 deg C) its viscosity is that of a HOT 40 weight.
Thicker is not inherently better. Long, technical story short, where oil viscosity is XwYY, X should be as low as possible. Even a cold 5 weight is still much thicker than a hot 40, so some people's belief that 0w__ and 5w__ oils are too thin for the 4.0 is false. YY can be 30 or 40, but 40 has been proven to not be inherently any better for the 4.0 than 30.
Now, you think that gear oil is thicker than motor oil because gear oil has ratings like 80w90. Gear oil isn't actually that much thicker. The ratings are so much different though because they are rated in a completely different way for different temps/circumstances. Regardless, you should NEVER use gear oil in the engine.
By running 15w40, your oil is needlessly thick when cold which could be producing increase wear during warm-up. Once it's hot, it's a 40 weight, and that is OK, but ultimately unnecessary. A 30 will protect just as well or perhaps even better and could provide a slight MPG boost.
Quoting myself from a thread on a different forum:
Also just to confirm, if I run rotella 0w40 over 5w30 in my cherokee, the 40 weight won't be too thick?
Thanks
Newbie
Quote:
Synthetic oil is NOT thinner. For example: 5w30 dino and 5w30 synthetic are the same viscosity. 10w40 dino and 10w40 synthetic are the same viscosity.
Moving on to what multi-viscosity ratings actually mean...
5w40 means that when COLD (0 deg C) its viscosity is that of a COLD 5 weight. When HOT (100 deg C) its viscosity is that of a HOT 40 weight.
Thicker is not inherently better. Long, technical story short, where oil viscosity is XwYY, X should be as low as possible. Even a cold 5 weight is still much thicker than a hot 40, so some people's belief that 0w__ and 5w__ oils are too thin for the 4.0 is false. YY can be 30 or 40, but 40 has been proven to not be inherently any better for the 4.0 than 30.
Now, you think that gear oil is thicker than motor oil because gear oil has ratings like 80w90. Gear oil isn't actually that much thicker. The ratings are so much different though because they are rated in a completely different way for different temps/circumstances. Regardless, you should NEVER use gear oil in the engine.
By running 15w40, your oil is needlessly thick when cold which could be producing increase wear during warm-up. Once it's hot, it's a 40 weight, and that is OK, but ultimately unnecessary. A 30 will protect just as well or perhaps even better and could provide a slight MPG boost.
Quoting myself from a thread on a different forum:
Sorry to necropost but I've been doing a lot of reading on what oil I need to use on the Cherokee and this guy seems to know his stuff. But is he talking about this when he says "yellow bottle"? They have a lot of different options and "yellow bottle" doesn't really narrow it down to anything specific. They have platinum, synthetic, ultra, etc.. It's all so confusing and I want to make sure I take care of her. She's a 2000 with 128k miles and we just got her earlier this week so I'm trying to get to a nice starting point on all the maintenance so I know everything has been done (oil, all other fluids, air filter, ground wires, rust removal/protection, etc). Originally Posted by mschi772
The misconceptions! You need oil Jesus.Synthetic oil is NOT thinner. For example: 5w30 dino and 5w30 synthetic are the same viscosity. 10w40 dino and 10w40 synthetic are the same viscosity.
Moving on to what multi-viscosity ratings actually mean...
5w40 means that when COLD (0 deg C) its viscosity is that of a COLD 5 weight. When HOT (100 deg C) its viscosity is that of a HOT 40 weight.
Thicker is not inherently better. Long, technical story short, where oil viscosity is XwYY, X should be as low as possible. Even a cold 5 weight is still much thicker than a hot 40, so some people's belief that 0w__ and 5w__ oils are too thin for the 4.0 is false. YY can be 30 or 40, but 40 has been proven to not be inherently any better for the 4.0 than 30.
Now, you think that gear oil is thicker than motor oil because gear oil has ratings like 80w90. Gear oil isn't actually that much thicker. The ratings are so much different though because they are rated in a completely different way for different temps/circumstances. Regardless, you should NEVER use gear oil in the engine.
By running 15w40, your oil is needlessly thick when cold which could be producing increase wear during warm-up. Once it's hot, it's a 40 weight, and that is OK, but ultimately unnecessary. A 30 will protect just as well or perhaps even better and could provide a slight MPG boost.
Quoting myself from a thread on a different forum:
makros
Junior Member
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Apr 6, 2026
- Join DateDec 2023
- LocationLos Angeles CA
- Posts:75
- Year1990, 1995
- ModelCherokee (XJ)
- Engine4.0
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Likes:225
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Liked:15 Times in 12 Posts
I love replying to old threads, for historical interest.
I got a gallon of Shell Rotella T4 10W-30 Diesel Engine Oil on sale at AutoZone for $18 in August 2024 in Los Angeles, California.
It was on sale at Walmart for $16 but I would have had to drive farther.
I got a gallon of Shell Rotella T4 10W-30 Diesel Engine Oil on sale at AutoZone for $18 in August 2024 in Los Angeles, California.
It was on sale at Walmart for $16 but I would have had to drive farther.