1. If I have low oil pressure at idle (low as in "check gauges" light comes on) but get about 35-40 psi at around 2000 rpm, would adding a quart of lucas to my next oil change help increase oil pressure at idle?
2. If I add lucas once, do I need to keep adding it every oil change? Is it something like when you start using it, you can never go back?

I have a 2000 Jeep Cherokee with the 4.0L. Only 109,000 miles. No ticking, clattering, or knocking. Past owner blew the head gasket and coolant leaked into the oil, wearing away some of the bearings. I asked a mechanic if I should up from 10w-30 to 10w-40, and he said 10w-30 with a quart of lucas would be a better option. I already changed the oil pressure sending unit, I have seafoam in the crankcase to help get any sludge blocking the oil pump, and the mechanical pressure test confirmed the gauge is reading correctly.

If the lucas doesn't work, I plan on installing a Melling High Volume oil pump, which I'm told worked wonders in similar situations (yes, i know volume does not equal pressure, and it may lead to other problems down the road, but 90% of the people who install them say they solve the oil pressure problem. Basically my back is to the wall right now- I can't even sit at a red light for 3 seconds without having to rev the engine to 1000 rpm's or so, and it only gets worse with the upcoming summer heat (I'll be in Montgomery this summer)). If anyone has any experience with these oil pumps, that advice would be greatly appreciated too.

 

I switched from 10w30 to 15w40 diesel oil and it increased my oil pressure by 10 psi. I would recommend that over adding Lucas additive.

 

First you don’t want seafoam in your oil thats a wonderfully way to destroy your bearings . Second 15w 40 until death or an immediate rebuild/swap would be my choice . Used engines are cheap my last XJ held 30 psi with over 210k at idle after hours and hours of driving . If you checked with a mechanical gauge and have zero or less than 10 you can forget a HVOP and rebuild or replace .

 

Nothing wrong with putting Seafoam in the oil to clean the engine out, that's what it's made for. Just don't leave it in for more than 1000 miles or so.

 

Also what kind of oil filter are you using?

 

Wrong . It’s meant to be put in right before an oil change say 20 minutes prior ... I don’t reccomend using it at all.

 

I'll vouch for this stuff, too.
https://www.cherokeeforum.com/f2/rev...ormula-130469/

 

Wrong.

"For best results, we recommend adding to oil 100 to 300 miles before every oil change."

https://seafoamsales.com/product/sea...fuel-additive/

 

I have had good luck using marvel mystery oil. Cleaned up my MJs nasty gunk buildup very well.

 

Do you know how the past owner diagnosed a blown head gasket? The 2000-2001 had the infamous 0331 head which has a defect between cylinder 3-4 which can (but does not always) lead to cracking.

Are you currently having to add any coolant to the coolant reservoir? If you are, you may have a cracked cylinder head which is front and center in figuring out........

 

if you think that it’s a good idea to put in your oil at any time you’re wrong IMHO I wouldn’t run it for 30 seconds . There’s not a bottle of anything that’s going to cure sludge . I have done a mix of ATF and diesel fuel as a last resort before on a near death sludged up engine .... all it did was block up dozens of oil filters before it finally lost oil pressure for a few minutes too long and blew up . Prolong the inevitable if that’s your cup of tea.

 

I personally have used Lucas on every 4.0 I have owned, but it does nothing for oil pressure. As stated above run 15w40 Rotella oil and a wix filter. You'll be good to go.