Oil - What'll this do??

ParadiseXJ

New member
OK, so I made a rookie mistake when I did my oil change yesterday...I'm not sure if I need to fix it or not, my MJ...4.0...AW4...190K

I bought the oil off of a display at the Zone. All (almost all) the jugs said 10/30. I also grabbed the sixth quart off the rack. Drained the oil, changed the filter, cleaned it all up, added the quart first, then opened the jug and started pouring...

...as I was pouring I noticed the JUG of oil was 5/30, not the 10/30 I thought I had. So the question is obvious. Is the 5/30 too thin or should I just run it. Ambient temps in the summer here run from a low of 40F to a high of 105F.

Should I change it, or leave it??
 

Buddha.

New member
If your truck usually runs a bit hot and you work it hard it *might* be a problem. The hotter the engine gets the thinner the oil will be. I don't know how accurate the stock oil pressure guages are but I'd keep an eye on it.
 

ParadiseXJ

New member
I was running Rotella 15/40 and the pressure was good. After my usual drive to work of 22 miles it was 45+ all the time. When I took it for a drive after my oil change the pressure was lower...before it got up to 200.

I do not drive it hard, but it's very hilly around here (since I live in the hills) and it gets up and over 210-220 occasionally.

So should I drain SOME out and throw in some 15/40. How bout some Lucas "additive" How much thinner, really is 5/30 as opposed to 10/30??
 

Tim_MN

Freakish Hand Strength
NAXJA Member
Use the Google for the scientific version. The first number is the cold viscosity, the second number is the hot viscosity. Both numbers are 30, at running temperatures, both oils are equal.

I would run 10/40 in hot climates, and 20/50 in high mileage engines in hot climates.
 

md21722

NAXJA Member
NAXJA Member
There is not going to be that much difference between 5w-30 and 10w-30 for what you've chosen. If you normally run 10w-30 and have 5 quarts 10w-30 and 1 quart 5w-30 then I wouldn't worry about it. If in your climate you notice that hot idle oil pressure is exceptionally low, I would change to a higher viscosity such as 15w-40.

Some additional information. SAE viscosities are allowed ranges, not specific values. The ranges have a 20% spread and overlap to some degree. For example, a thick xw-30 can be a little thicker at operating temperature than a thin xw-40. However, most of these variations are seen when different specifications are desired. A "Euro" or diesel formulated xw-30 is likely to be thicker than a "domestic" gasoline engine oil. Between domestic gasoline oil formulations there is not going to be much difference. One of the differences is the amount of VI needed to achieve the wider viscosity brand. And since VI tends to break down over time, the more shear stable viscosities tend to be those with a narrower viscosity range (i.e. 10w-30 vs 5w-30) or those that start off with a thicker base stock to begin with (i.e. 5w-40). Keep in mind that it can take 3X longer for oil to reach operating temperature than the coolant. For example, here in Colorado for in town driving, my coolant may read 210F in about 5 minutes but it takes 15-20 minutes for hot oil pressure to reach is normal value.
 

Hillbilly XJ

New member
Putting additives of any kind in oil is a total waste of money, modern oils have everything needed in them out of the bottle. Only bigger waste of money is the "Snake Oil" called Amszoil, I can't spell it for sure.

Just run what you have till your next oil change.
 

md21722

NAXJA Member
NAXJA Member
Amsoil is just one of many synthetic oils available. While the cost of synthetic may be considered a waste to some, synthetics do provide benefits and some prefer to use them.
 

Hellbent

New member
The "5" has little-to-nothing to do with the viscosity of the oil when it's at operating temperature.
Just run it. Neither you nor the motor will notice any difference. :)
 

93gc40

New member
It's summer now, and you live in California.. That first number, the 5, is meaningless. The 5 is for cold starts in COLD weather. Now the 30 part could be an issue if it leads to a reduced oil pressure. If that is the case then change up to something with a bigger second number. 5/30, 10/30, 15/30 are all the same once the motor warms up. They will ONLY act differently for the first 2-5 minutes after cold motor start-up, or the weather turns sub 30 degrees.
 

SonicCougar99

New member
I had my RMS and oil pan gasket done at a local shop about a year and a half ago (I had previously done valve cover gasket about a month prior), and they refilled it with 5W-30 and I didn't say anything ahead of time. I was right at 200,000 miles and the 5W-30 was perfectly fine, in fact I got just a touch better gas mileage and my oil pressures looked better as well. This was late Fall in northern AZ so temps ranged from lows in the upper-20's/mid-40's to highs from 50's to upper-70's.

As for the Amsoil comment, I don't get it either. I run all Amsoil fluids in my Cougar and don't have any issues. Full synthetic and I got it all at good prices because I had the "Preferred Customer" card.
 

Tim_MN

Freakish Hand Strength
NAXJA Member
Oil is oil. High cost synthetic oils and "special" oil additives do not add benefits in relation to their cost.

I run whatever oil is on sale at WalMart. My 1999 has 210,000 + miles and my 2000 has 135,000 miles. 5/w30 for winter, and 10w/40 for summer.

Regular oil changes are more important than the name on the bottle.
 

Talyn

New member
Oil is not oil and there is definitely a difference in brand and oil specifications. ZDDP content, longevity, shear strength, etc. The Walmart branded shit is not the same as Brad Penn, or Joe Gibb's or Amsoil in anything but the term oil.

However, what the OP did won't hurt anything.
 

BulletMaker

New member
So engine oil that has two numbers usually the first is low, like 5 followed by a W and then a second number. The first number is the "startup viscosity" the W is put in there saying it's a "winterized" oil. Since it's summer, the second number (the hot viscosity) is really all that matters.

FYI, the winterizing additives do nothing but make oil stick to parts, giving it a 5weight viscosity for startup. I typically run 10W30 in winter, and SAE30 in summer.
 

Tim_MN

Freakish Hand Strength
NAXJA Member
Oil is Oil.

If the oil meets the current or recent API engine oil specifications, it meets specifications. The 4.0 is not a high tech engine, it is an improved 1960's design that will last many miles with proper maintenance in the form of regular oil changes.

+210,000 miles using whatever oil was on sale. Regular oil changes are more important than the name on the bottle.
 

BulletMaker

New member
Talyn,

Well, he is sort of right, oil is oil, what really matters to most of us is what's mixed in with it in the form of detergent additives, temperature modifiers, viscosity improvers.

There's a reason why no one seems to be advocating using SAE30 bar and chain oil in the crank case.
 

BulletMaker

New member
So after spending a bit more time researching oil and thoroughly giving myself a headache. Here's something I didn't know that hasn't even been brought up yet:

http://www.pqiamerica.com/Labels.htm

The "service class" of the oil. It seems most of our renix jeeps are going to want either SF or SG class oils which are currently obsolete. The current generation of oils is SN.
 
Top