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Have a 4.0 engine with 188,000 miles on it. Runs great but has low oil pressure after warmed up. Question is, would it hurt to go with 15-40 rotella at next change? I'am in the very hot mohave desert of so. Cal. I have 10w30 in it now
 

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How low? They run 13 psi at idle and rise accordingly with engine rpms.
 

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Have a 4.0 engine with 188,000 miles on it. Runs great but has low oil pressure after warmed up. Question is, would it hurt to go with 15-40 rotella at next change? I'am in the very hot mohave desert of so. Cal. I have 10w30 in it now
YMMV of course but I have run 15-40 diesel-spec oil in every vehicle I've owned since the early '80s and never had any serious engine problems with any of them...not counting stuff that was worn out when I bought it, LOL. I'm told that it will clog up the cat if your engine is burning some oil but it hasn't happened to me so far. May cost a fraction of an MPG and cranks a little harder in the winter (shouldn't affect you) but I'll gladly pay that price for the protection it gives.
 

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YMMV of course but I have run 15-40 diesel-spec oil in every vehicle I've owned since the early '80s and never had any serious engine problems with any of them...not counting stuff that was worn out when I bought it, LOL. I'm told that it will clog up the cat if your engine is burning some oil but it hasn't happened to me so far. May cost a fraction of an MPG and cranks a little harder in the winter (shouldn't affect you) but I'll gladly pay that price for the protection I think it gives.
Fixed that for accuracy.:)
 

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Try 10W40 next oil change and see if it helps.

There is now Rotella motor oil formulated for gasoline engines.
Although I typically use Valvoline Maxlife synthetic blend I might give it a try. Unfortunately it is currently only available in thinner viscosities such as 0W20, 5W20 and 5W30.
 

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Amsoil all the way
Avon, Mary Kay and Fuller Brushes too.

After all, if it sells only by multi-level marketing and never in stores it must be good.
 

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IMO..At that miles, you could go to 10W-40 easily. Low oil pressure is probably more related to wear. Not a fan of running Diesel certified oil in Gas engines; Rotella did launch a Gas engine version recently.
 

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Have a 4.0 engine with 188,000 miles on it. Runs great but has low oil pressure after warmed up. Question is, would it hurt to go with 15-40 rotella at next change? I'am in the very hot mohave desert of so. Cal. I have 10w30 in it now
To answer your question... No. I don't think it would hurt your engine at all. However I would double check engine specs for oil pressure to verify it is out of spec. If your engine is running properly. I'd leave it be. If not, you could bump up the weight.

I don't think paying for a better brand of oil really matters if the car is just a DD. I hear that rotella is better on valve seats than mobile 1, etc. For me though its just hear say. I use a Zinc additive on all my oil changes personally. Unless you are racing, I don't think you would see the added benefits of the better oils such as AMSoil or Lucas. If you wheel in the desert that would be another story though.

My honest .02
 

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Rotella 15W40 is a great oil, and might help. In areas where the weather dips below 30F in the winter I would recommend 0w40 or 5W40 however.

A couple of questions come to mind:

What was the oil pressure?

How was it determined?

The factory dash oil pressure gauge is not good for determining oil pressure, you need to verify it with an accurate mechanical oil pressure gauge, if you haven't already done so. Get the oil pressure readings you're supposed to have when the oil is hot, usually after about 20-30 minutes of driving, and at the rpms specified in the shop manual. That is really the only way to know if you have a problem with low oil pressure. Bumping up a grade might help, take readings with the 15W40 as well should you go that route.

Another product that is good at raising oil pressure in older engines and has some added value is Schaeffer's #132. However if there is a real problem like bad bearings or a faulty oil pump, thicker oil or the additive is a temporary fix at best.
 

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And you have owned how many gasoline engines since 1980? Your experience in this particular field -- practical experience, hands-on, nothing else counts -- is...??? Educate me.
18 Jeeps and at least 50 cars. Can I get a copy of the data you've compiled in the book you wrote on this subject? If not...:mooning:
 

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Discussion Starter #14
heavy oil

YMMV of course but I have run 15-40 diesel-spec oil in every vehicle I've owned since the early '80s and never had any serious engine problems with any of them...not counting stuff that was worn out when I bought it, LOL. I'm told that it will clog up the cat if your engine is burning some oil but it hasn't happened to me so far. May cost a fraction of an MPG and cranks a little harder in the winter (shouldn't affect you) but I'll gladly pay that price for the protection it gives.
think i'll use 5 qts rotella 15-40 and a quart of hy-per lube! so hot around here it should do the job
 

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I will just live this here don't want to start a new "oil viscosity" discussion.
IMO for hot climates, towing, offroading- "oil cap" +10+20 for hot viscosity.
 

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I will just live this here don't want to start a new "oil viscosity" discussion.
IMO for hot climates, towing, offroading- "oil cap" +10+20 for hot viscosity.
That looks like a visc chart from a 1970s GM manual. 5w-30 for temps less than 60 only. Now we're told it's too viscous for most cars, with 0w- and 5w-20 common, and -16 coming. Crazy.

But the 4.0 is an old design.
 

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Have a 4.0 engine with 188,000 miles on it. Runs great but has low oil pressure after warmed up. Question is, would it hurt to go with 15-40 rotella at next change? I'am in the very hot mohave desert of so. Cal. I have 10w30 in it now
Exactly what oil pressure at what rpms are you concerned with? You're getting a lot of advice without anyone knowing exactly what oil pressure you're considering too low.
 

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That looks like a visc chart from a 1970s GM manual. 5w-30 for temps less than 60 only. Now we're told it's too viscous for most cars, with 0w- and 5w-20 common, and -16 coming. Crazy.

But the 4.0 is an old design.
Its probably from the 90s but I assure you nothing has really changed, this chart can be found in any OM prior to "one oil does all" madness.
5W30 is ok up to 100f, above excessive engine wear would occur.
0W is a good choice in Canada, In California for ex even 5W is excessive probably 10W is what is needed - no real winter, no freezing but we get the same "oil cap viscosity" as someone in Canada or Alaska.
 

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Its probably from the 90s but I assure you nothing has really changed, this chart can be found in any OM prior to "one oil does all" madness.
5W30 is ok up to 100f, above excessive engine wear would occur.
0W is a good choice in Canada, In California for ex even 5W is excessive probably 10W is what is needed - no real winter, no freezing but we get the same "oil cap viscosity" as someone in Canada or Alaska.
X2. One more fact to keep in mind is the higher the viscosity the harder it is to pump and the more time it takes to circulate and reach all the nooks and crannies in an engine. Using a higher oil viscosity than the engine manufacturer recommends is rarely a good idea.
 
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