Two questions for you all.

[homesoon]

1. How often do you all change your engine oil?

I just bought a 2003 Jeep Liberty Renegade with 228k miles (some will call me crazy), and I just did an oil change on it. I used the Mobil 1 High Mileage 5W-30 Full Synthetic oil with the Mobil 1 Oil Filter, I was thinking around maybe 5K mile intervals?

2. Any idea what's causing my heater to blow barely warm air?

You can't feel any warmth at all until it gets to operating temperature (coolant temp is at middle of gauge) and even then, it feels only minorly warm, and when at a red light, it stops going warm completely after around 15-20 seconds.

Coolant looks almost new.

 

[Damotee]

I change the engine oil and filter every 5K kilometres, so about every 3.5K miles.
Given you have just bought his Jeep and it has fairly high mileage, I'd go ahead and replace both diff oils and the transmission oil and filter. (ATF4 transmission oil). Id also change the air filter, plus all coils and spark plugs as these are cheap.

I'm not sure about an answer to your second question, sorry.

 

[JasonJ]

I'd never go past 4000 miles on a 3.7l for an OCI. Too much risk of sludging or oil consumption dropping the level too low. Even with synthetics...

For your heater core issue, first make sure it's up to level... if it's low, it'll do what you describe. If it's old, it can do that as well. If none of those pan out, next thought is that it may be partially clogged, and there are ways to address that before ripping it out and replacing it.

 

[homesoon]

I change the engine oil and filter every 5K kilometres, so about every 3.5K miles.
Given you have just bought his Jeep and it has fairly high mileage, I'd go ahead and replace both diff oils and the transmission oil and filter. (ATF4 transmission oil). Id also change the air filter, plus all coils and spark plugs as these are cheap.

I'm not sure about an answer to your second question, sorry.

In regards to spark plugs, which ones do you personally use?

 

[HoosierJeeper]

Always copper NGK.

 

[LibertyTC]

KJ Likes These! :gr_grin:
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[uss2defiant]

1. 3-4k OIC
2. unless you know the how it was previously maintain, I'd get the coolant flush. Could be a blend door issue?

 

[Joenavy85]

1. How often do you all change your engine oil?

I change mine every 7500 miles. Mobil 1 5w-30 High Mileage. Every other change I take a sample and send to Blackstone Labs in Indiana for testing.

2. Any idea what's causing my heater to blow barely warm air?

when at a red light, it stops going warm completely after around 15-20 seconds.

Losing heat at a red light is indicative of low coolant level. $20 says that if you pop it in neutral and rev the engine you'll get heat for a little bit. The higher engine speed pumps more coolant, and your heater core is the first place to stop receiving it as the level drops. Check the weep hole on your water pump to see if the seal is leaking, as the pump may be going bad.

 

[Joenavy85]

unless you know the how it was previously maintain, I'd get the coolant flush

This, for all the fluids (oil, transfer case, trans, diffs)

 

[nohitter64]

Make sure you use HOAT coolant!!!!

 

[04Liberty]

Mobil1 5W-30 every 6000 miles with filter change. Ran like a top, no sludge til the ex-wife took off with it. The trick was making sure she warmed it up and didn't just get in and go for short hops. I use this same interval for my hemis.

 

[u2slow]

I use standard 5w30 changed with the filter about every 3500-5000km. Been doing that for the last 95,000km.

I prefer to change cheaper oil more often than longer intervals with synth. It gets me out there (and under there) to check it over better, grease things, rotate/switch tires, and look for upcoming problems.