In my experience it was during my break in period on all my vehicles that they seem to use more oil and require more frequent oil checks. on my jk I have been down as far as 1/2 quart in 3k miles. The manual say oil change at 6k but I do all vehicles at 3k. An oil change is cheaper than an engine my dealer says 6k oil changes are only recomended for cool weather climates, 3k is for warm to hot climates.

typically the amount of oil will depend on the engine size and the operating temp of the engine. yes it is for lubrication and heat disipation. think of it this was my wife nissan has 4quarts (4cyl), the ford f150 triton 5.4 takes 9 quarts (V8) runs @ 180deg, chevy duramax diesel 6.6L takes 14 quarts runs at 230deg and higher

I would love to have more oil in the JK but the oil pan is already low enough

 

The reason for the JKs having 6 quarts rather than 3 is kind of a combination of a few of the things you pointed out (but none of which should worry anyone about getting a little low on oil). The engine will not run appreciably hotter with less oil (maybe 5 or 10 degrees F but not enough that it will hurt anything). Also the oil itself will not break down any faster than it would with a larger starting volume (as essentially the same internal conditions of the engine will lead to the same chemical kinetics a.k.a. rate of oil break-down). BUT having a larger starting volume of good oil allows more oil to "break down" without worry of the oil as a whole in the engine being anywhere close to out of spec. So having a larger starting volume of oil (6 quarts rather than 3) allows you to run the engines hotter (a.k.a. more horsepower), longer (more miles between oil changes), or both in the same engine. So I wouldn't worry about running my engine with 3 quarts rather than 6 from a mechanical perspective. However, since the oil would break down at the same rate, having half the oil in the engine would require the oil to be changed twice as often to keep it within spec.

Also the BMW you speak of that takes 9 quarts, I will guarantee you that it makes more horsepower than our JKs , but does it also call for oil change intervals beyond 3,000 miles (I'm curious as I know VWs call for 5,000 - 10,000 miles between changes)? When I used to change oil, I changed the oil in a Ford Powerstroke once or twice that called for really long oil change intervals around 15,000 miles or so but it has a HUGE 16 or so quart pan to accommodate this . So you can easily run an engine on less oil than the pan holds (especially with modern synthetic oils) I just wouldn't do it if you can help it as you never know if going over a bump or up a hill could shift the oil level below what the oil pick-up can reach thus dropping oil pressure to 0 and destroying the engine...

 

To sum it all up....

The OP's engine is fine. Just don't make a habit of it.

 

So I think I'm starting to get a picture of how the oil distribution system works. Lemme see if I have this right...


There is a certain volume of oil in the pan, well above what is strictly needed. There is an oil pickup tube somewhere in that pan towards the bottom, but not all the way down to avoid picking up sludge and other debris. When you start the engine, the oil is sucked up the pickup tube, through the filter, and taken to where it needs to go to lubricate the engine.

So as long as there is oil at or above the pickup tube (not just when you start the engine, but also when much of the oil has been sucked up and is being circulated), the oil pressure will remain constant, even if there is barely enough oil to clear the tube. It will run a little hotter, because there will be less of the oil to dissipate the heat, but not enough to make a difference (in a normal climate? What about extreme climates?).

The oil will not actually break down faster, but because there is less of it, the oil will reach an out of spec state faster than if there was more of it.

If the pickup tube ever fails to suck in oil or sucks up air with the oil (like the level is almost too low or moves back and borth on bumps) the oil pressure to the engine will be compromised and the idiot low oil light will go on, but by that time it's too late because the engine hasn't gotten enough oil and damage has occured.

So the reason to have a lot more oil than strictly necessary is so it will last longer, run a bit cooler and never run the risk of there not being enough to reach the pickup even under extreme conditions (such as hills where oil pools on one side of the pan).

Is that about right?

So if it is right, and I had 2.5-3 quarts of oil in the pan, as long as the oil didn't break down (thank god for Mobil 1! ), I would be fine, but if something happened, like for example I took it four wheeling, and I went up a steep hill, and the oil pooled on one side of the pan and the pickup tube sucked air, I would have killed my engine?

 

Yep, precisely! This is mostly why I run synthetic. Not so much for less wear under normal conditions, but most of us do have things going on in our lives beyond our Jeep. When we do and say forget to check the oil level in the Jeep every week, it is just a little extra buffer that in your case paid off big time! A little extra cost for synthetic oil quite possibly saved your oil from going out of spec enough to let your engine blow

 

I've been running Pennzoil Platnium in my vehicles for years now. Alot of independent tests at www.bobistheoilguys.com give it high ratings.

I'll check it once a week or so and use my "trip B" button on the odometer that I reset to 0 with every oil change which lands between 4k to 5k.

I find the "trip B" method really good to keep tabs of where I'm at vs. oil consumption.

 

Right. gotta keep oil at the pump's pickup. Things like angles (hill climbs) and g-force (drag racing or high speed turns) affect this which is another reason for more volume of oil, and windage trays, baffles, etc. (among other things).

No. a tranny that's down a pint or two will start slipping. And they typically hold a lot of fluid counting the torque converter. I assume it all has to do with pressure.

 

gotcha. hey, where in TX are you moving to?

 

the last 2 oil change i did i was down 2 qt. last time i put 5w30 to see if make a differ

 

I just changed the oil yesterday and only got out about 2.5 litres. Scared the crap out of me.

But after reading this thread, I feel better, need to start monitoring the oil level more closely.