A colder engine will absolutely reduce fuel economy. Colder engine = colder oil = thicker oil. Thinner oil gives better fuel economy which is why cars once used 40ASE oil and many now use 0W-20... The AMC 4.0 should ideally be about 210f or somewhere between 205f and 220f....So to be clear, at 165f you are getting lower MPGs, producing less HP and probably incurring marginally more engine wear than at factory 210f temp.
Thanks for the insight. I actually did not consider the weight or temperature of the engine oil hurting the MPG. I was focused more on the way the fuel system operates. Open/ Close Loop etc. I would like to see some actual real life data on how much the oil weight/ temp affects MPG. Do you know of any good RUclips videos or web sites that could shed more light on this subject?
@@wrenchestoadventures O2 sensors don't work until they warm up from exhaust heat or their internal heating element. So until they start sending a signal the engine runs in open loop. Then switches to closed loop once it sees a reliable signal coming from the sensors. The engine may also go to open loop during hard acceleration. Viscosity of engine oil effects MPG because thicker oil creates more patristic drag on the engine. It takes more energy for the rings to wipe oil from cylinder walls. A thicker oil film adds mass to reciprocating engine components. Thicker oil causes more massive droplets of oil to be flying around the engine. Which saps more power from rotating and reciprocating engine components as they strike those more massive droplets. Also thicker oil requires more H.P. to pump. All these issues may seem trivial, but they're not. If you were to double the viscosity of an engine's oil it would likely quadruple oil induced parasitic drag.
I agree with you on how the o2 sensors work in relation to open/close loop. As well as under hard acceleration it does switch back to open in order to affectively supply the max amount of fuel. Thanks for the explanation on how the oil affects the MPG. I definitely learned something about it. What you said all makes sense to me. I wish there was an easy way to test MPG at different engine and oil temperatures. I’d like to see how much it actually affects the MPG.
I went a little overkill, went with the 4 hole Ksuspension injectors, upgraded 42kv ignition Coil with iridium spark plugs, new wires and distributor Cap, new fuel pump, all filters, fresh oils everywhere, 2/0 wire everywhere and 160A alternator, and bigger group 34 battery, stock 3.55 Gear Ratio with 235/75R15 tires and I've got 21 mpg on highway driving conservatively
A lift, a roof rack and the added weight of a winch and all the mods plus bigger rolling resistance because of large tires turn the XJ into a parachute going down the road
@@wrenchestoadventuresyes. Bosch plugs especially iridium are known to cause knocking and wear quickly in the 4.0L. this tractor engine likes regular copper plugs
I'm not sure what to make of the MPG thing. I keep reading 13 MPG is a high for many people. I picked up a '99 XJ last month and have been getting ready for upgrades. With 225K miles on it, the last couple of 100 miles or further trips I have taken it on, it's getting 19 mpg highway. Most of my driving is putting around 30 mph or slower on the gravel with it, taking pictures and letting my dog do his thing in new places. Even then it seems to be like 15 mpg or so. Am I blessed? Crazy? Is my carbon fiber foot oddly light on fuel even if not on momentum? Lifters were rattling pretty good when I got it, solved 50% of that with a dose of Marvel Mystery. Doesn't seem to use oil, doesn't leave any clouds on hard acceleration or deceleration..... So I'm upgrading everything else first. 4 1/2 inch lift and 33's come this week. Winch bumper, lockers, a few little touches, will be ready for snooping around old logging roads and such in the mountains...... when the engine goes, or when I'm ready to drop the coin, she will get a 4.7 stroker upgrade.
Is it safe to assume your XJ is currently stock? Based on your MPG that makes me believe that it is. The thing that kills the MPG the most on a XJ, are lifts, gears, and bigger tires. You also need to think about how much extra weight in gear you’re carrying around too. Especially if you are out camping. Anyways, it sounds like you’re building a pretty cool XJ. Good Luck with your build.
Does that blue parts XJ have a good front drive shaft? Also good video man I really need to do injectors and some heat shielding for sure to help with some heat soak for sure and some better MPG can’t hurt for sure
Yeah new fuel injectors and some heat shielding for them makes a big difference. Also I’m pretty sure the front drive shaft is good on the Blue Cherokee. Do you need one? Email me and we can talk more about it. wrenchestoadventures@gmail.com
Stop running wide tires! Run 10.5 or 11’s get away from the 12 plus… if anyone says you need 12’s to off road are just silly. I’ve done everting in 10.5’s… just air down. And it helps if you’re running Danna 30 or 35 rear. Run the better fuel injectors I believe come in a Neon, it has 4 holes, and insure you’re cooling. Now that I have an LS I don’t have to deal with the 4.0 anymore. I put 1.3 million miles on my 4.0.. I drove 17 hours round trip every weekend for 10 years. The biggest thing was tires! 12 inch wide tires will kill your gas…
I agree, tire size does make a big difference. But I guess there is a trade off. You can't always find a narrower tire, especially in the bigger tires 37" and larger. At that point you just have to except your MPG is going suffer. HAHA
That's awesome! It just goes to show with a little maintenance on our old Jeeps they get so much better MPG. What year Jeep do you have? And how many miles are on it?
No, I’m running 4.10 gears, and 35’s. I do also drive my XJ a little harder than most I think. I haven’t corrected my speedo gear ether. It’s only off by a couple mph.
Rather then putting open vents like that look at what semi truck sleepers use,those vents yuou can open and close,find them at and semi truck parts store.
No worries 👍🏻 I bought them off Amazon. There’s a video on my channel about them ruclips.net/video/2R04PLXDhbk/видео.htmlsi=aoovG_-xpxdBuB6c . The link to them is in the description.
i read that about the operating temp and what temp it enters closed loop a long time ago on a thread on the NAXJA forums. the internet is completly full of crap on that issue, if you say its ok to run cooler or run anything other than a 195° thermostat you get attacked. Good to see other XJ owners just not willing to believe whatever some dingleberry posts in a FB group. nice work
Yeah it’s crazy how much misinformation is out there. There are so many key board warriors out there on FB and forums pretending like they know what they are talking about. And then attacking others if their information is challenged. Most of them don’t even know what a FSM is haha. I’m glad you liked the video!
@@wrenchestoadventures what are the tags that you searched? I tried to find a couple of my area/Idaho but nothing comes up. I’m willing to travel up to six hours.
I just searched Np241j, or Rubicon Transfer case. They are super rare to find. I’ve only seen a couple. I passed one up a year ago. So when this one popped up I rushed to get it. They are pretty common on eBay.
A colder engine will absolutely reduce fuel economy. Colder engine = colder oil = thicker oil. Thinner oil gives better fuel economy which is why cars once used 40ASE oil and many now use 0W-20... The AMC 4.0 should ideally be about 210f or somewhere between 205f and 220f....So to be clear, at 165f you are getting lower MPGs, producing less HP and probably incurring marginally more engine wear than at factory 210f temp.
Thanks for the insight. I actually did not consider the weight or temperature of the engine oil hurting the MPG. I was focused more on the way the fuel system operates. Open/ Close Loop etc. I would like to see some actual real life data on how much the oil weight/ temp affects MPG. Do you know of any good RUclips videos or web sites that could shed more light on this subject?
@@wrenchestoadventures that's not how it works. Learn more about how and when the computer runs in closed/open.
Can you explain what you mean? I have a very good understanding of how the system works.
@@wrenchestoadventures O2 sensors don't work until they warm up from exhaust heat or their internal heating element. So until they start sending a signal the engine runs in open loop. Then switches to closed loop once it sees a reliable signal coming from the sensors. The engine may also go to open loop during hard acceleration.
Viscosity of engine oil effects MPG because thicker oil creates more patristic drag on the engine. It takes more energy for the rings to wipe oil from cylinder walls. A thicker oil film adds mass to reciprocating engine components. Thicker oil causes more massive droplets of oil to be flying around the engine. Which saps more power from rotating and reciprocating engine components as they strike those more massive droplets. Also thicker oil requires more H.P. to pump.
All these issues may seem trivial, but they're not. If you were to double the viscosity of an engine's oil it would likely quadruple oil induced parasitic drag.
I agree with you on how the o2 sensors work in relation to open/close loop. As well as under hard acceleration it does switch back to open in order to affectively supply the max amount of fuel.
Thanks for the explanation on how the oil affects the MPG. I definitely learned something about it. What you said all makes sense to me. I wish there was an easy way to test MPG at different engine and oil temperatures. I’d like to see how much it actually affects the MPG.
I went a little overkill, went with the 4 hole Ksuspension injectors, upgraded 42kv ignition Coil with iridium spark plugs, new wires and distributor Cap, new fuel pump, all filters, fresh oils everywhere, 2/0 wire everywhere and 160A alternator, and bigger group 34 battery, stock 3.55 Gear Ratio with 235/75R15 tires and I've got 21 mpg on highway driving conservatively
That’s awesome, now you don’t have to worry about anything for a while. 21 mpg is great! What was your mpg before all the upgrades and maintenance?
I got 12 hole injectors from Ksuspension, 62mm TB, k/n filter, new ngk sensors (all!), MSD coil, 0w40 oil,
Awesome! Where did you buy your 62mm throttle body? Also why did you opt for 0w40 oil?
Thanks for the great information and contents!
You’re welcome! 👍🏻
Love learning about our jeeps! Thanks👊🏽
Yeah no problem 👍🏻 You’re definitely going to like the next video then!
A lift, a roof rack and the added weight of a winch and all the mods plus bigger rolling resistance because of large tires turn the XJ into a parachute going down the road
Haha yeah aerodynamics is not a trait the XJ has.
I believe the nkg cooper is best for the 4.0L
I think you mean NGK Copper? I haven’t tried those in a 4.0. Do they hold up better than the Bosch plugs?
@@wrenchestoadventuresyes. Bosch plugs especially iridium are known to cause knocking and wear quickly in the 4.0L. this tractor engine likes regular copper plugs
Try Valvoline VR1 oil instead of using a zddp additive. Too much zddp can be bad for flat tapper engines.
Interesting, I didn’t know that. I’m due for an oil change. I’ll check out that oil you mentioned.
That's true but how much is to much idk
I'm not sure what to make of the MPG thing. I keep reading 13 MPG is a high for many people. I picked up a '99 XJ last month and have been getting ready for upgrades. With 225K miles on it, the last couple of 100 miles or further trips I have taken it on, it's getting 19 mpg highway. Most of my driving is putting around 30 mph or slower on the gravel with it, taking pictures and letting my dog do his thing in new places. Even then it seems to be like 15 mpg or so. Am I blessed? Crazy? Is my carbon fiber foot oddly light on fuel even if not on momentum? Lifters were rattling pretty good when I got it, solved 50% of that with a dose of Marvel Mystery. Doesn't seem to use oil, doesn't leave any clouds on hard acceleration or deceleration..... So I'm upgrading everything else first. 4 1/2 inch lift and 33's come this week. Winch bumper, lockers, a few little touches, will be ready for snooping around old logging roads and such in the mountains...... when the engine goes, or when I'm ready to drop the coin, she will get a 4.7 stroker upgrade.
Is it safe to assume your XJ is currently stock? Based on your MPG that makes me believe that it is. The thing that kills the MPG the most on a XJ, are lifts, gears, and bigger tires. You also need to think about how much extra weight in gear you’re carrying around too. Especially if you are out camping.
Anyways, it sounds like you’re building a pretty cool XJ. Good Luck with your build.
Champion Copper plugs are better for 4.0
I’ve never tried Champion Copper plugs. Where do you buy them at?
Buy them at Auto Zone think any Auto parts store sells them
Does that blue parts XJ have a good front drive shaft? Also good video man I really need to do injectors and some heat shielding for sure to help with some heat soak for sure and some better MPG can’t hurt for sure
Yeah new fuel injectors and some heat shielding for them makes a big difference. Also I’m pretty sure the front drive shaft is good on the Blue Cherokee. Do you need one? Email me and we can talk more about it. wrenchestoadventures@gmail.com
@@wrenchestoadventures ya I need to for sure get to that soon. And ok I just sent you an email man
Stop running wide tires! Run 10.5 or 11’s get away from the 12 plus… if anyone says you need 12’s to off road are just silly. I’ve done everting in 10.5’s… just air down. And it helps if you’re running Danna 30 or 35 rear.
Run the better fuel injectors I believe come in a Neon, it has 4 holes, and insure you’re cooling.
Now that I have an LS I don’t have to deal with the 4.0 anymore.
I put 1.3 million miles on my 4.0.. I drove 17 hours round trip every weekend for 10 years. The biggest thing was tires! 12 inch wide tires will kill your gas…
I agree, tire size does make a big difference. But I guess there is a trade off. You can't always find a narrower tire, especially in the bigger tires 37" and larger. At that point you just have to except your MPG is going suffer. HAHA
I use brisk racing spark plugs.
They are pricey tho.
I’m not familiar with those spark plugs, I’ll look them up
Same bro those things are tazers they burn all the fuel efficiently
I flushed my cooling system...new hoses, new radiator, the works. I am getting about 1.5 better mpg.
That's awesome! It just goes to show with a little maintenance on our old Jeeps they get so much better MPG. What year Jeep do you have? And how many miles are on it?
@@wrenchestoadventures I have a 98 limited 4 cylinder diesel, with 140k kilometers.
Oh cool, that’s awesome that it’s diesel!
@wrenchestoadventures yeah. Um trying to find ways to make more power. Unfortunately there is 0 aftermarket support 😞
Dang, that’d be cool to see it making more power.
Are you still running stock gears? My '91 on 35's, 4.88 gears, and speedo gear corrected averages 16mph.
No, I’m running 4.10 gears, and 35’s. I do also drive my XJ a little harder than most I think. I haven’t corrected my speedo gear ether. It’s only off by a couple mph.
Rather then putting open vents like that look at what semi truck sleepers use,those vents yuou can open and close,find them at and semi truck parts store.
off subject.. where did you get the hood vents?
No worries 👍🏻 I bought them off Amazon. There’s a video on my channel about them ruclips.net/video/2R04PLXDhbk/видео.htmlsi=aoovG_-xpxdBuB6c . The link to them is in the description.
i read that about the operating temp and what temp it enters closed loop a long time ago on a thread on the NAXJA forums. the internet is completly full of crap on that issue, if you say its ok to run cooler or run anything other than a 195° thermostat you get attacked. Good to see other XJ owners just not willing to believe whatever some dingleberry posts in a FB group. nice work
Yeah it’s crazy how much misinformation is out there. There are so many key board warriors out there on FB and forums pretending like they know what they are talking about. And then attacking others if their information is challenged. Most of them don’t even know what a FSM is haha. I’m glad you liked the video!
62mm throttle body, aids in improving mileage
I never thought about getting a larger throttle body. I’ll look into them. Thanks!
No doors works too for better mpg just saying...
I’ll be testing that theory on my Comanche haha
@wrenchestoadventures some states require bars, but all 4 off the xj, it is a noticeable difference
My xj has so many mods and armor, I'll never get decent fuel economy.
Yeah I’m in that same boat! The best I can do is 13.8 MPG.
Is that a Jk Rubicon case or TJ?
TJ Rubicon case, it’ll be going on the Comanche.
@@wrenchestoadventuressweet. I’ve been looking forever. Where did you find yours
I found locally here in Utah. It was on Facebook marketplace.
@@wrenchestoadventures what are the tags that you searched? I tried to find a couple of my area/Idaho but nothing comes up. I’m willing to travel up to six hours.
I just searched Np241j, or Rubicon Transfer case. They are super rare to find. I’ve only seen a couple. I passed one up a year ago. So when this one popped up I rushed to get it. They are pretty common on eBay.
1:don’t drive it
2:don’t drive it
3:don’t drive it
That’s one way to get better MPG 😂
For God's sake, stand still. I felt drunk watching you bouncing around.
Thanks for the feedback. I did notice that too while I was editing the video. Looks like I have go pee haha I’ll work on that going forward.