Oil Light comes on at Idle but not above 1000rpm's

[blue_kjR417]

I changed my oil about 300 miles ago from conventional to full synthetic and recently my oil light in the dash has been coming on when my kj is at idle (about 750 rpm's) if I give it the least amount of gas it goes off usually once past 1k rpm's what could be causing this? is it gonna hurt my motor? how can i fix it? I've checked the dipstick the oil level is fine, no leaks either.

 

[KYLiberty]

Most likely it's the oil pressure sender going bad. It's happened to a bunch of us.

 

[yellocoyote]

Yep. Replaced mine last spring because it went out over the winter. I also had a leak underneath... if you look under the hood, you may have signs of a leak around the oil filter. The sending unit is just above the filter.

Not expensive to replace at all.

 

[wingnuts]

culprit can also be a change to full synthetic

 

[LibertyOrDeath]

What it the weight of the oil. 0W-20 by chance?

 

[snowsport]

culprit can also be a change to full synthetic

how?

 

[wingnuts]

I don't remember the specifics, but do remember reading at some point that synthetic oil responds differently and can actually cause a lower oil pressure at lower RPMs because it is less viscious but does a better job lubricating

 

[blue_kjR417]

What it the weight of the oil. 0W-20 by chance?

10w-30

 

[LibertyOrDeath]

10w-30

Hmm. IIRC stock calls for 5W-30. Could be the issue but I doubt it. What are the temps in you area? If it's really cold that could affect it.

Are you getting this light at operating temps or while warming up.

 

[2003KJ]

I don't remember the specifics, but do remember reading at some point that synthetic oil responds differently and can actually cause a lower oil pressure at lower RPMs because it is less viscious but does a better job lubricating

Switching from conventional to synthetic will not affect the pressure at all, provided you stay with the same weight. If you go from say a 10W-30 to a 5W-30 you MIGHT notice about a 1psi difference in hot pressure after a long highway run. For the most part though, that minor of a change you'll see no difference. This is the same no matter what type you run, conventional, full synthetic, or blend.

Now if you go from a 10W-30 to say a 0W-30 (not recommended unless you've got a diesel) then yes, you should see a noticeable difference in pressure readings, and it will be lower. The opposite of course if you go to a higher weight, like a 15W-whatever (again not recommended..especially this time of year).

My guess, you've got a bad sender unit. You're seeing the light come on once it's got up to temp and the oil has naturally thinned out a little bit. If it's knocking and making all kinds of bad noises, then you've got a problem. From what i'm seeing though, the sender units tend to go out on the KJ for some reason. Pretty cheap and easy fix.