webejeepin

Great thread....here comes the newbie question...Business Card test? I gota' ask???

Thanks

Mr.T

Partly because of the temp differences of where I go, mountains in winter and desert in summer.

Some like higher viscosity at operating temp because oil consumption and blow-by are less, or because the engine is quieter. But as I wrote earlier, higher viscosity is mostly an insurance bet for me. The premium is at most a tiny loss of MPG. The payoff comes at rare events when oil temps are abnormally high, such as cooling system trouble. I suspect that rare events are when most engines fail and/or endure lots of wear.

To illustrate, here's a hypothetical example using a viscosity calculator. Let's take two synthetic oils, Amsoil XLM 5w-20 and ALF 5w-40, and plug their numbers into the viscosity calculator. Now let's presume a hypothetical engine will fail under some given RPM/Torque if the viscosity is less than 5 cSt. Using the calculator, 5w-20 is 5 cSt at 268 deg F (131 C). The 5w-40 is 5 cSt at 320 deg F (160 C), 52 deg F higher oil temp.

Mr.T

Blot some oil on white paper (not glossy). Let it soak in, look at the stain under a lamp, or with a lamp behind the paper. Yes, it's subjective and relies on experience, but it's cheap.

Edit: googled oil test business card, here's an interesting link apparently quoted from "The Lubrication Field Test and Inspection Guide"

webejeepin

I'll give it a try...any advice on what to look for?

Timing is great, I'm at 5,000KM and due for an oil change. I love learning new stuff like this.

Mr.T

Just googled oil test business card, found this article quoted from "The Lubrication Field Test and Inspection Guide"

webejeepin

Thank you kind Sir.

I'll be giving this a try...sounds like fun.

Hack12

So, I'm pretty green when it comes to engine issues, specifically oil differences. I've been using synthetic 5W-20, as recommended, and recently noticed my oil light came on when I was approaching a stop, even though it had only been about 4k miles since my last change. After immediately bringing my car to be checked, they noticed that I only had about 1qt of oil left. They changed my oil and the oil light stopped sporadically coming on. However, this would mean my engine is burning approximately 1.25qts of oil per 1k miles. My questions are:

1. Is this normal for JK's?

2. If not, is this dangerous and how do I fix it?

3. What is the difference between 5W-20, 30, & 40 and which should I really be using in my 3.8?

4. I live in New England, i.e. hot in the summer and freezing in the winter. Should I be using different types of oil during different seasons?

5. Does the type of filter they put in make a difference and what kind would be best for my JK?

Thanks for the help and sorry for the extremely basic questions.

webejeepin

Search 'oil sucking' on this forum...tons of info here to help explain the issue.

Alot of us have 3.8L that use (burn oil), for various reasons.

After oil consumption test(s), and lots of patience my dealer re-built my motor, under warranty. I no longer burn oil like I did...450 ml of oil per 750 KM traveled.

Since this happened to me, I've gotten back to basics....checking my oil once a week (min) like clock work!!

Mr.T

These are really advanced questions

Here's my 2 cents:

No engine this size should consume that much oil. That kind of consumption often leads to engine damage because it's hard for everyone driving it to constantly remember to check/add oil.

Oil consumption is hard to diagnose and fix because there are so many causes and the solutions often involve major engine work.

Try going to bobistheoilguy.com and read up on what the oil numbers on labels actually mean.

Oil filters are important, and there are stories about [cheap] filters failing internally.

If it were my Jeep, I'd flush the engine with some Amsoil engine flush (or equivalent, per the directions). This may free up sticking piston rings if that's the cause. Change the oil to a 5w-40 or 0w-40 (whatever brand you like) and use it year round. This will tend to consume less oil and reduce blow-by compared to 5w-20. Blow-by carries oil mist through the PCV valve and into the intake manifold. Optionally inspect/change/clean the PCV valve. Change the filter to something quality like the Amsoil that's designed to run for long oil change intervals.

Check the engine for significant leaks, and see what happens to oil consumption.

Side note, I have no affiliation with Amsoil. Their prices are often higher than competitors, and some devotees are a bit weird, but the product quality is there IMHO and the specs are published.

Mr.T

Good points regarding the advantages of regular samples and trending. But, oil sampling is also expensive at around $30. The cost/benefit ratio isn't the same in a jeep compared to aircraft, marine, and industrial equipment.

I'd argue that even a single sample has valuable information when compared with similar engines. For instance, one can easily see from the singular data in the first post that this engine has normal to below normal wear particles in oil, and therefore is in pretty good condition and the oil is doing a good job of lubrication.