I think 15w-40 in my jeep was a mistake

[930.engineering]

Depends. I could feel in VW EA888 engine every time I bump from XW30 to XW40. So jump of some 0.2-0.3 cP. You can feel the turbo kind of needing a split second more to spool.
In BMW I cannot feel that, in Toyota too. Also could not feel that in my BMW twin-turbo diesel. But in VW with EA888, I could absolutely feel it.

My exact same experience. Back in 2017 at roughly 400 km I used Shell Helix Ultra Professional AV-L 0W-30 (= Pennzoil Platinum Euro LX) and swapped it at roughly 1000 km with Ravenol RUP 5W-40. KV100 11.9 vs 14.3, HTHS 3.5 vs 3.9 - yes, it`s noticeable. Sluggishness is a hard word, but I feel it.
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[ka9mnx]

Otherwise use a 5w40 syn (but not a Euro oil nor diesel oil).

What's the issue you have with Euro oil?

 

[Chris142]

I think you're reading or interpreting it wrong. In any case, your owners manual oil recommendations are decades obsolete. 5w30 oils have gotten much better. You could run a modern 5w30 syn year round just fine, especially if it's a 5w30 that is on the thick end of 30 grade.

Examples:
Quaker State Ultimate Protection 5w30 (thick for a 30).
Castrol Edge 10w30 (thicker for a 30).
Shell Rotella Multivehicle 5w30 (thickest for a 30).

Otherwise use a 5w40 syn (but not a Euro oil nor diesel oil).

P.S. - A friend of mine owned a Jeep that I sold him at 93K miles. He drove it to 410K miles (no rebuild) using Supertech syn 5w30, which is much thinner than the 5w30s I recommended. He drove it all over Nevada, Arizona, and California for 14 years until he reached 410K miles. Clearly modern 5w30 is fine in a 4L, even in hot weather, even using a cheap thin 5w30 oil.

The excellent syn 5w30 oils I recommended to you are thicker, more robust, and better than Supertech 5w30. The 5w40 syns are also more excellent than Supertech 5w30.

Even so, ST 5w30 was good enough to go 410K miles in a hot climate. So what are you worried about? You don't need 15w40. Furthermore, 15w40 is a terrible idea because it won't always be a hot day. Cold snaps happen. Night time happens.

Use 15w40 if you want, but you'll be doing your 4L engine no favors, especially at cold start on any day that's not hot, or cold starts in early morning or at night.

Thankfully it's summer here and a cold start is 90F. I had the oil... Many others on various forums raved about 15w 40 in the jeep so I used it.

It's definitely too thick is all.

I am aware that the 4.0 will generally run forever on anything oily.

For fun here is a pic of the antiquated owners manual recommendations.

 

[cheesepuffs2]

A Jeep 4L isn't a diesel engine. If you want a thicker oil for it then use a thick per grade 5w30 syn or a 5w40 syn. I belonged to a Jeep club. We did offroading. 5w40 syn and thick for the grade 5w30 syn were commonly used in Jeep 4L and 4.6L strokers with good success in a wide variety of climates on & off road.

A Jeep stroker engine builder told me he'd prefer people use 5w30 in the 4L & 4.6L strokers he builds.

15w40 isn't needed for summer anywhere. If you're worried about summer heat use 5w40 syn or a thick for grade 5w30 syn.

That said, if you live somewhere with hot summers. 15w40 could work, but so would 5w40 or a thick 5w30. 15w40 would not be better, even on a hot day. If an unexpected cold spell comes along, 5w40 has you covered. 5w40 is good year round in any climate for 4L.

Let me put that another way. There's nothing that 15w40 (conv) can do that 5w40 (syn) or a thick 5w30 (syn) can't do as good or better in hot weather. In moderate weather (or at night) 5w40 or thick 5w30 is better at cold start. In cold weather 5w40 or thick 5w30 is good. In cold weather 15w40 is bad, especially for a gas engine.

I think you're misinterpreting the point that I tried to make and moving the goalposts. I'm not saying that 15W does anything "better" in hot weather than a 5W. But the idea that you can't safely use a 15W oil, in warmer ambient temps especially, is unnecessary fear.

There are several published lubrication charts that position 15W-40 as being appropriate down to 5 degrees Fahrenheit. The 0W oils that are common today provide a huge safety margin and are good for pumpability down to -40 F. The level of cold that these oils can handle is lower than you seem to think.

You know how many Harley-Davidsons we all see on the road all the time? They spec 20W-50 even still today, and people fire them up and romp on them immediately, and they still don't have lubrication failure from a lack of oil flow in the first few minutes of run time.

 

[IndyFan]

My owners manual says 10w30 down to 0F and not to use 5w30 over 32f.

Yep, many model years said that. Many also said 5w30 all around. Either way, that motor will run and run and run.

 

[cheesepuffs2]

To those saying placebo effect, disagree. I can tell very definitively that my Honda J35 feels draggier on 5W-30 back to back with 5W-20. Maybe it can't be felt as much with certain engines, or certain people are less in tune with their vehicles, but what OP is describing is 100% legitimate.

 

[Carlostrece]

There are several published lubrication charts that position 15W-40 as being appropriate down to 5 degrees Fahrenheit.

In a diesel truck maybe. Are those 15w40 charts for a Jeep 4L gas engine?

You know how many Harley-Davidsons we all see on the road all the time? They spec 20W-50 even still today, and people fire them up and romp on them immediately, and they still don't have lubrication failure from a lack of oil flow in the first few minutes of run titime.

A Jeep 4L isn't a Harley engine.

So who's moving the goal post? I'm talking about Jeep 4L specifically, which the topic of this thread. You're invoking other engines.

 

[Carlostrece]

Thankfully it's summer here and a cold start is 90F. I had the oil... Many others on various forums raved about 15w 40 in the jeep so I used it.

It's definitely too thick is all.

I am aware that the 4.0 will generally run forever on anything oily.

For fun here is a pic of the antiquated owners manual recommendations.

View attachment 287763

If your cold starts are 90F then yes it's fine. At least during the daytime. I don't know how cold your nights are. You might need to do a cold start at night or early morning sometimes. I wouldn't worry about cold starts that are 70F or higher. Probably somewhat colder would be fine too.

 

[melk]

What I was running 15 years ago

 

[Carlostrece]

To OP. Compare the data sheets for 15w40, 10w40, 5w40, 10w30, & 5w30. Compare the KV100 cSt and KV40 cSt of each.

Let us know how comparable the KV100 cSt is for those 5 grades. We already know they're not comparable at KV40, but I think you'll see they differ considerably at KV100.

 

[ripcord]

People often perceive what they expect to perceive. The placibo effect is very real. Not calling anyone out specifically, but just saying.

Stepping up a grade of oil might cost at most a couple of horsepower at normal cruise around RPMs. Nobody has a butt-dyno that's calibrated to that fine of a level.

Folks who think that a particular oil significantly affects power should try using a acceleration app to compare 0 to 60 speeds.

 

[cheesepuffs2]

In a diesel truck maybe. Are those 15w40 charts for a Jeep 4L gas engine?


A Jeep 4L isn't a Harley engine.

So who's moving the goal post? I'm talking about Jeep 4L specifically, which the topic of this thread. You're invoking other engines.

It isn't an engine thing, it's a viscosity thing. Talking cold cranking and pumpability floors as defined by grade.

I think the fear-mongering here is just hilarious sometimes. You're telling somebody that 15W might not even be suitable for summer night-time starts now. Alrighty. Implying that the safe ambient temperature for a 15W starts at 90 degrees Fahrenheit is ridiculous. What's the entire suitable range then, 90 to 160 degrees?

 

[Carlostrece]

It isn't an engine thing, it's a viscosity thing. Talking cold cranking and pumpability floors as defined by grade.

I think the fear-mongering here is just hilarious sometimes. You're telling somebody that 15W might not even be suitable for summer night-time starts now. Alrighty. Implying that the safe ambient temperature for a 15W starts at 90 degrees Fahrenheit is ridiculous. What's the entire suitable range then, 90 to 160 degrees?

I never said it wasn't safe at 90F during the day. In fact I said it is. Stop putting words in my mouth and read more carefully. You're really getting on my nerves now.

Are you aware that many desert climates that are hot in daytime get cold at night? Sometimes even down to freezing or colder.

I don't know the specifics of his climate. I don't know how cold it gets at night and early morning where OP lives. He might want to start it during those times too.

 

[cheesepuffs2]

Are you aware that many desert climates that are hot in daytime get cold at night? Sometimes even down to freezing or colder. I don't know the specifics of his climate.

No, it's funny, that's actually the very first I'm ever hearing of this.

 

[Carlostrece]

No, it's funny, that's actually the very first I'm ever hearing of this.

Well now you learned something, unless you're just being sarcastic. Google it if you don't believe me.

 

[IndyIan]

How many miles on the 10W30? It may have been pretty thin at the end of a long OCI?
If you do track mileage, it would be interesting to see if there's a measurable difference in mileage over a whole OCI? With 90F cold starts, I don't think there's any downside to running 15W40 except potentially a very slight mileage hit? I bet in a couple days you won't notice anything at all.

 

[cheesepuffs2]

Well now you learned something, unless you're just being sarcastic. Google it if you don't believe me.

I was being sarcastic. Thanks for the refresher though.

 

[MNgopher]

If your cold starts are 90F then yes it's fine. At least during the daytime. I don't know how cold your nights are. You might need to do a cold start at night or early morning sometimes. I wouldn't worry about cold starts that are 70F or higher. Probably somewhat colder would be fine too.

We are worried about cold starts at 70F on a 15w40 oil?

Sheesh... There would be diesels everywhere here with issues with this type of guidance... Some of the stuff on this board is amusing...

 

[BC1]

15w-40 is good to down to 10F. No where in California will it be 10 during the summer. I doubt any where in the northern hemisphere will get that cold.

 

[cheesepuffs2]

We are worried about cold starts at 70F on a 15w40 oil?

Sheesh... There would be diesels everywhere here with issues with this type of guidance... Some of the stuff on this board is amusing...

Save your breath, I already tried.