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B_Mulls

What type of fluids?

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Some of you may know, I just bought my Comanche. I finally have some time to take it into the shop and work on it. I have some questions about what fluids I should put in, and what other basic stuff I should check out.

 

I'm a rather novice mechanic, the most complicated thing I’ve ever done was change some disc brakes which is basically undoing a few bolts. 

 

Ive done some research and saw the MJ calls for 10w30 or 10w40. I have no clue wether to put synthetic or conventional oil in.

 

If anyone has some basic tips, and I mean pretty darn basic, I would greatly appreciate it. I don’t want to mess up a rust free MJ.

 

Thanks in advance.

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This can of worms question is one you'll ask three people and get six answers, none of them incorrect.

 

Factory called for 10w30 or 5w30 in climates that regularly see 0°F or less.

Stepping up to a 5 or 10w40 may help increase oil pressure if you're seeing low pressure on the gauge, but there are slight efficiency losses because it takes more hp to pump it. I'm not as convinced a 40 will make your engine last longer than a 30 will as some people seem to be, but it's not going to hurt it to run it. 

Some people will recommend diesel oils as well. Engine oils have changed a bit in the last 30 years, and modern diesel oils contain ZDDP (zinc) levels that are more consistent with gasoline oils from 30 years ago, which can be beneficial to cams and lifters, and modern gasoline oils don't necessarily have the ZDDP the engine manufacturers initially wanted. Diesel oils are also much higher in detergents, so do a decent job of keeping your engine clean inside. Modern gas oils have moved away from ZDDP because it's mildly damaging to your catalytic converter, and will lead to reduced cat life, which could be a concern were e-testing is required.

 

Synthetic or conventional is your choice. Synthetics are more expensive but the fluid properties are more consistent and the oil has a longer wear life before it breaks down. You won't kill it running conventional. 

Which brings me to a bigger point. What you put in it is less important than maintaining proper maintenance schedules. You can use cheap oil and filters and be fine if you're changing every 3000 miles, or you can use expensive synthetics and probably run twice that between changes without a problem. 

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I used to be a guy who obsessed over oil. These days I just run whatever reputable brand 10w30 full synthetic or synthetic blend comes on sale around the time I need to change the oil. I run either a Wix, Mopar, or Bosch oil filter depending on what kind of mood I'm in. I run about 3.5 to 5k intervals, since that's about as long as I can go without adding a quart and it seems about right for the 1960s tech of the engine.

 

What really matters is that you do change the oil on time, don't run it out of oil, and have a little bit of mechanical sympathy. The 2.5L and 4.0L are durable engines that in my experience don't give a rat's @$$ what oil you put in it, as long as there's something in the crankcase and you're making decent oil pressure. Although depending on your luck, that last part might be optional. There are plenty of 2.5L and 4.0L engines running around on 13psi of hot idle oil pressure and not suffering too much.

 

As for transmission fluid, I've always used Valvoline MaxLife Dex-Merc in my AW4. I'd strongly recommend an automatic transmission cooler of some type for all AW4 owners as the transmission tends to run hot even when not pulling heavy loads. That'll do much more to keep it alive than what brand of fluid you put in.

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I agree that the maintenance schedule is more important than what you put in. Especially if the truck sees offroad use or temperature extremes.

 

Engine: Mobil1 10w30 

Filter (4.0L): Wix 51085

Clutch and Brakes: ATE 200

MT: Redline MT-90

Xfer Case: Dex III (any)

Diffs: Mobil1 75w90

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1 hour ago, DesertRat1991 said:

I agree that the maintenance schedule is more important than what you put in. Especially if the truck sees offroad use or temperature extremes.

 

Engine: Mobil1 10w30 

Filter (4.0L): Wix 51085

Clutch and Brakes: ATE 200

MT: Dex III (any)

Xfer Case: Redline MT-90

Diffs: Mobil1 75w90

 

This brings up another question, differential fluid.

 

What type of fluid should I put in, and do I really need to change it?

 

Also if anyone has any general maintenance tips I would greatly appreciate it.

 

thanks all for the responses!

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You should change all your fluids if you haven't already and like stated above, keep a maintenance schedule, and yes that includes your diff fluid.  The brands of what you use are less important but if you use a higher quality fluid, usually they are going to last longer or perform better.  

 

Oil - 10w-30 or whatever else like stated above.

Trans - Auto Trans fluid for AW4.

Manual trans - MT-90 or 10W-30 motor oil for AX-5 or AX-15.  Not sure what the BA10 calls for.

T-Case - ATF or some form of 30 weight motor oil.

Differentials - 75W-90 gear oil

Clutch/Brakes - DOT 3 brake fluid

Coolant - the green kind.  Buy concentrate and mix water to 50/50 yourself.

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The diffs care even less about what's in them than the engine. Go for gear oil, 75w90, 80w90, whatever. If you load up your truck frequently with heavy towing or hauling you could go for 75w140 but there shouldn't be anything wrong with the 90. If you've got a limited slip diff you'll want to add friction modifier to the gear oil, but if you've got stock diffs it's probably safe to assume they're not limited-slip. 

Its a good idea to pop the diff covers and dump them when you pick up a new Jeep... somehow I keep managing to buy jeeps that "haven't really been off-road" that have diffs full of water. Water isn't great for differentials, and there aren't many ways it gets in, and almost none of them involve clean water. 

 

That said, unless you see a lot of dusty environments or do a lot of water crossings, once you know it's got clean oil in it, the factory change interval is huge. Diffs are pretty simple mechanisms and don't really produce their own contaminants, unlike an engine or even transmission. Just making sure the level is fine is usually enough for street machines. 

 

As far as the rest of the fluids go, it's usually best on a new purchase to at least make sure they're all there. I like to change them out myself (see above about diffs full of water) but if your coolant is a nice bright colour and nothing looks milky or murky it's probably fine for now. Brake fluid's a big one that gets ignored a lot too. Bleeding the brakes out and replacing the fluid has been a big improvement on brakes on a few of my vehicles that have been neglected. 

 

As for other tips, there's a big thread full of them pinned to the top of this sub-forum.  

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33 minutes ago, Dzimm said:

 

Coolant - the green kind.  Buy concentrate and mix water to 50/50 yourself.

I'd recommend using distilled water with that conentrate, your tap water has impurities which can/may lead to rust issues in the cooling system. 

Distilled can be bought in any grocery store.

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The other advantage over running an antifreeze coolant over just straight water in addition to the higher boiling point is it's loaded with rust inhibitors. 

Ideally you'd mix it with de-ionized water which some parts stores will carry, but distilled is fine and a ton cheaper. Just read the label at the grocery store, because I've seen some that have minerals added back for "health"... because that doesn't defeat the purpose of distilled water at all...

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I dug out my maintenance papers and here's a list of every fluid that's in my '91. Just for completion's sake. Ditto that you should probably change everything and write when you did it and what you put in.

 

Engine: Castrol High-Mileage Synthetic Blend 10W30 (it was on sale). I think I used a Bosch filter this time around.

Auto Trans: Valvoline MaxLife Dex/Merc. It's important to note that it will take multiple changes to cycle the old fluid out. You get around half of it by draining the pan.

Rear Differential: Store brand 75W90. A Dana 35 has a lot more things to worry about than what fluid you put in it. Add LSD additive if you have one, but the clutches are probably worn out on it anyway.

Brake Fluid: DOT3 of whatever brand, it's all the same stuff. Trade out your bottles every now and then and don't leave the cap off for long, because brake fluid absorbs moisture from the air. Moisture in brake fluid is bad.

Coolant: Store brand conventional green. Bought as concentrate and mixed 50/50 with distilled water. About a dollar a gallon at a grocery store. On a stock Jeep engine I don't see a whole lot of need for the newer fancy coolants. Green stuff has always worked for me.

Power Steering: Store brand power steering fluid.

Washer Fluid: The orange kind. Use a couple of brands and find whatever you like best... or whatever looks the tastiest.

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5 hours ago, Minuit said:

I dug out my maintenance papers and here's a list of every fluid that's in my '91. Just for completion's sake. Ditto that you should probably change everything and write when you did it and what you put in.

 

Engine: Castrol High-Mileage Synthetic Blend 10W30 (it was on sale). I think I used a Bosch filter this time around.

Auto Trans: Valvoline MaxLife Dex/Merc. It's important to note that it will take multiple changes to cycle the old fluid out. You get around half of it by draining the pan.

Rear Differential: Store brand 75W90. A Dana 35 has a lot more things to worry about than what fluid you put in it. Add LSD additive if you have one, but the clutches are probably worn out on it anyway.

Brake Fluid: DOT3 of whatever brand, it's all the same stuff. Trade out your bottles every now and then and don't leave the cap off for long, because brake fluid absorbs moisture from the air. Moisture in brake fluid is bad.

Coolant: Store brand conventional green. Bought as concentrate and mixed 50/50 with distilled water. About a dollar a gallon at a grocery store. On a stock Jeep engine I don't see a whole lot of need for the newer fancy coolants. Green stuff has always worked for me.

Power Steering: Store brand power steering fluid.

Washer Fluid: The orange kind. Use a couple of brands and find whatever you like best... or whatever looks the tastiest.

 

This was really helpful. Thank you!

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Any brand name motor oil is way better than even 10 years ago. I do run Shell Rotella T6 in my XJ. I did run Shell Rotella 15W-40 and 10W-30. If you engine leaks oil, then run conventional. Otherwise sort of a flip of the coin. I do run synthetics about 7,500 miles, and a synthetic oil filter (NAPA Platinum).  I do use Zerex Z05 radiator fluid. I have a Ford Contour and MB 240D, so that works in them too. I do use distilled water to mix 50/50. The Z05 can be mixed for more extreme heat. I'd probably run 10W-30 from October to March, then 10W -40 in the summer. More for starting. I do run 15W-40 in the MB in the summer months, the 10W-30 when temps get colder. Yes, it makes a difference in that motor for starting. You did not mention where you are located at. That could determine what oil(s) to run. 

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On 3/24/2019 at 5:32 PM, B_Mulls said:

 

This was really helpful. Thank you!

You mentioned being a novice mechanic. You have a nice truck that's worth keeping nice. The best way to do that is to have good maintenance habits. Here's what works for me:

alKTAJFl.jpg

 

I print out these sheets for every vehicle under my care and go around the vehicle filling them out every couple of months. Anything I do that's of note gets written down. "Oh, I guess I'll change the oil next week" or "I think I remember changing the oil last month..." is how engines get gunked up and full of sludge because if people are good at one thing, it's forgetting important details. If I have any doubt, I just look at the most recent sheet and know exactly when I need to change fluids.

 

If anyone wants a PDF of that sheet, let me know.

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4 hours ago, Minuit said:

You mentioned being a novice mechanic. You have a nice truck that's worth keeping nice. The best way to do that is to have good maintenance habits. Here's what works for me:

alKTAJFl.jpg

 

I print out these sheets for every vehicle under my care and go around the vehicle filling them out every couple of months. Anything I do that's of note gets written down. "Oh, I guess I'll change the oil next week" or "I think I remember changing the oil last month..." is how engines get gunked up and full of sludge because if people are good at one thing, it's forgetting important details. If I have any doubt, I just look at the most recent sheet and know exactly when I need to change fluids.

 

If anyone wants a PDF of that sheet, let me know.

Holy cow this is genius!  I've always just written down what I did and the date in a list, which gets hard to track after a while.  Never thought to actually do multipoint inspection checklists like actual mechanics do...  I would greatly appreciate a PDF copy.  PM sent, thanks!

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