Oil pressure

[Angry_bucktooth]

So I've tried researching this and I've found some kind of answers but nothing exactly.

 

Our trucks at start up have about 40-50 for oil pressure and at idle it drops to about 10 right.

 

I'm asking cause my truck on start up goes to 40/50 and when driving on the highway stays about 40 but when I drive around town it fluctuates between 20 and 40 and at idle it sits at about 10.

 

My truck is an 1988 pioneer 2.5l 5spd 4x4.

 

Sorry if this question has been asked all I can find it's stuff about the senders being the wrong ones (cluster swap) and I saw one post from eagle that kinda said my oil pressure was normal but wasn't real clear. I just wanna make sure it's fine or if I got a problem. Until it's sits at zero I'm not to worried but rather have no worry

[Eagle]

Your pressure is basically fine, for a 28-year old engine.

 

Factory spec is 13 psi minimum at idle, 37 to 75 psi above 1600 RPM (at operating temperature). So your warm idle is a touch below spec, but not unreasonable. It's the pressure while driiving that's of more concern. The faster the engine turns, the more oil pressure it generates. For NEW engines, around 50 to 55 psi at 60 to 65 MPH seems to be about the norm. 40 psi on the highway is lower than what we expect from a new engine, but you don't have a new engine.

[mikekaz1]

Eh, My Chevy van (2014) is normally dead on 40psi no matter the speed, been like that since I got it with 7miles on it. With hard pulls going up to 50 psi or so. Only After running all day, it may drop to 30 at idle but never any lower.

[Eagle]

Eh, My Chevy van (2014) is normally dead on 40psi no matter the speed, been like that since I got it with 7miles on it. With hard pulls going up to 50 psi or so. Only After running all day, it may drop to 30 at idle but never any lower.

But we're talking about a 1988 Jeep, not a 2014 Chevy. The Chevy might have a different type of pump.

 

I cited the factory service manual spec for oil pressure. If you don't believe me, look it up for yourself.

[mikekaz1]

Oh I understand, I was just stating. Even my new van, is right in line with "like new" jeep pressures. I understand what they end up being now in time and what's still acceptable. Was just trying to give kind of a similar view from a different vehicle.

[Angry_bucktooth]

Your pressure is basically fine, for a 28-year old engine.

 

Factory spec is 13 psi minimum at idle, 37 to 75 psi above 1600 RPM (at operating temperature). So your warm idle is a touch below spec, but not unreasonable. It's the pressure while driiving that's of more concern. The faster the engine turns, the more oil pressure it generates. For NEW engines, around 50 to 55 psi at 60 to 65 MPH seems to be about the norm. 40 psi on the highway is lower than what we expect from a new engine, but you don't have a new engine.

 

That's a relief to know so I am alright and done have to worry about damage. Line I said in my first post it's really not a concern till I see zero and it doesn't move. So no I feel more comfortable driving. Also could I be a little below spec since when I turn my key to the on position the needle goes a little before zero line it got bumped to low in shipping

[Megadan]

The weight of the oil you run will make a difference too. If I run 10w-30 in the summer my oil pressure sits at about 15psi at idle once it's all good and hot. with 10w-40 it sits right at 20 at idle.  I actually have a more interesting issue of my oil pressure reading dropping as I drive at constant speed long enough to get the oil good at hot. 40-50, but will go down as low as 35.  Idle pressure still sits at 15-20 range though.  

[mikekaz1]

i too run 10w-40

[Marine1Texas]

I use synthetic Mobil 1 5W50. It idles when cold at 40 then after hot, it is right about 28 to 30. I been using this oil for 21 years now. Before I would use 15w50, since it gets hot here in Texas.

[Eagle]

That's a relief to know so I am alright and done have to worry about damage. Line I said in my first post it's really not a concern till I see zero and it doesn't move. So no I feel more comfortable driving.

Just to be clear -- you are "all right," but you're not "fine." Your idle pressure is below spec. That's to be expected on an old, probably high mileage engine, but the reason we expect it is that we expect moving parts to wear. While the minimum idle oil pressure is 13 psi, most healthy Jeep engines idle at around 20 to 25 psi. So you have some early warning signs -- IMHO you should start considering either dropping the pan and replacing the main bearings (or all the bearings, while you're in there), or start looking for a spare engine you can rebuild while the one you have still runs.

 

As others have commented, oil weight also matters. When my '88 went over 200,000 miles and the oil pressure started reading a bit lower than what it had been, I switched to Mobil-1 full synthetic in 15W50 weight, then I went over to Castrol 5W50. My oil pressure in the '88 still isn't where it was when new, but I'm now at 287,000 miles and I'm still within factory specs.

[Angry_bucktooth]

 

That's a relief to know so I am alright and done have to worry about damage. Line I said in my first post it's really not a concern till I see zero and it doesn't move. So no I feel more comfortable driving.

Just to be clear -- you are "all right," but you're not "fine." Your idle pressure is below spec. That's to be expected on an old, probably high mileage engine, but the reason we expect it is that we expect moving parts to wear. While the minimum idle oil pressure is 13 psi, most healthy Jeep engines idle at around 20 to 25 psi. So you have some early warning signs -- IMHO you should start considering either dropping the pan and replacing the main bearings (or all the bearings, while you're in there), or start looking for a spare engine you can rebuild while the one you have still runs.

 

As others have commented, oil weight also matters. When my '88 went over 200,000 miles and the oil pressure started reading a bit lower than what it had been, I switched to Mobil-1 full synthetic in 15W50 weight, then I went over to Castrol 5W50. My oil pressure in the '88 still isn't where it was when new, but I'm now at 287,000 miles and I'm still within factory specs.

What do you recommend for oil I have always done 5w30 in all vehicles during the winter months and 10w30 in summer. I have yet to do an oil change normally I did one every other month alot of work driving but I got laid off then hired at a new company with company vehicle.. I was going to use the motor medic motor flush at next oil change and then run 10w30 since I've read it can be better but I've seen 5w50 10w40 10w30 all different opinions the most common seems to be 10w30 that's why I was gonna use it next oil change also my jeep has 118000 miles on it the p/o said motor was rebuilt at 80k (her mechanic said it was best to do all gaskets and clean). So I have low miles for my 88 also 10psi is a quests since its between the 0 and first line at idle I have yet to run a mechanical gauge for a more accurate reading

[gogmorgo]

Going from 5w30 to 10w30 isn't going to do anything for your oil pressure except at cold startup. I'm currently running 5w40 in mine, and am a little overdue for a change, but winter's hanging on pretty good this year (got more snow again yesterday) and I'm waiting till it warms up a bit more so I can switch out to 15w40 for the summer.

I don't know where you live or what the climate's like but if you don't really drop below freezing too often you can likely get away with running 15w40 year-round, or if you don't see temperatures too often that would require a block heater, probably 10w40 will do you. In my own climate I run the risk of -40 from October to March, so 15w40 is right out, and then in the summer mid 90's aren't unusual, which is pushing the upper limits of comfort for 5w40. I'm also running Rotella diesel oil for the higher zinc (anti-wear) levels, and since the 5w40 is only available in synthetic, I can save a bit of money by switching back to conventional for the summer.

[Angry_bucktooth]

I live in Connecticut the coldest I've seen it in 24 years has been -10 after a wind chill factor

[gogmorgo]

Wind chill factor don't mean a damn to a machine, it just cools off a little quicker. I'd say you'll be fine with 10w40.

[Eagle]

Going from 5w30 to 10w30 isn't going to do anything for your oil pressure except at cold startup. I'm currently running 5w40 in mine, and am a little overdue for a change, but winter's hanging on pretty good this year (got more snow again yesterday) and I'm waiting till it warms up a bit more so I can switch out to 15w40 for the summer.

I don't know where you live or what the climate's like but if you don't really drop below freezing too often you can likely get away with running 15w40 year-round, or if you don't see temperatures too often that would require a block heater, probably 10w40 will do you. In my own climate I run the risk of -40 from October to March, so 15w40 is right out, and then in the summer mid 90's aren't unusual, which is pushing the upper limits of comfort for 5w40. I'm also running Rotella diesel oil for the higher zinc (anti-wear) levels, and since the 5w40 is only available in synthetic, I can save a bit of money by switching back to conventional for the summer.

For 1988 the factory recommendation was 10W30 or 10W40. When my '88 was new I ran 10W30 in the winter and 10W40 in the summer.

 

It does not sound like your engine was "rebuilt. There's a lot more to a rebuild than replacing gaskets -- like bearings, rings, valve job, etc. So basically you have 118,000 miles on the engine. AND ... remember that the 2.5L has more gear, so for every mile you drive, the engine spins around more times than a 4.0L would. You have a 5-speed, so your gears are 4.10s. My '88 4.0L 5-speed has 3.07 gears. In round numbers, your engine goes around 4 times for every 3 times mine goes around. So, since most of us use the 4.0L as the frame of reference, your rings and bearings have seen the equivalent of 157,000 miles. I think you should be running 10W40 as a minimum. If it were mine, I'd be running 20W50 for the summer, 10W40 for the winter.

 

New London must be in a micro climate. I'm outside New Haven -- we had several nights this past winter that were -10 without factoring "wind chill."

[mikekaz1]

I'm in Monson MA and we definitely hit multiple negative double digits between this and last winter (mainly last winter)

[Marine1Texas]

When I was stationed in Praha, Czech we used 0w30 and 0w40 Most places that falls below freezing 5W30 is good, however if you are losing that pressure from old age or the engine 5W40 would be good.(note in old VW bug engines they used 20w50 because of the sloppy low compression heads). The reason people go with 5 or 0 is cold starts for the first 15 to 30 secs of engine warm up, the oil is more free to move around those cold pistons, before the engine can heat up that oil. Places that common 0 degree's 0 works well. The price of the oil is no different unless you get a brand that makes it that way. That is why I just go with 5W50 mobile 1 all the time with all my trucks. I change my oil every 6 thousand miles and it is still golden color after 6000 in all 4 of my trucks. This is just my subjection.

[Eagle]

Most places that falls below freezing 5W30 is good, however if you are losing that pressure from old age or the engine 5W40 would be good. ... The reason people go with 5 or 0 is cold starts for the first 15 to 30 secs of engine warm up, the oil is more free to move around those cold pistons, before the engine can heat up that oil. Places that common 0 degree's 0 works well. The price of the oil is no different unless you get a brand that makes it that way. That is why I just go with 5W50 mobile 1 all the time with all my trucks.

Agreed. The first number in an oil designation is the cold viscosity, the second number is the operating temperature viscosity. So a 5W50 is thin like a 5-weight when cold, but still has the viscosity of a 50-weight when hot. Like Noriyori, I run 5W50 (I use Castrol Syntec) in the high mileage engines to compensate for loss of oil pressure due to worn bearings.

[schardein]

I have to admit that I believe sometimes people overthink the whole oil question.

 

I went to school 27 years ago to be a mechanic.  There is an old adage, "10 psi for every 1000 rpm".  So 8-10 psi at an idle is probably ok, regardless of what the factory specs call for.

 

I buy cheap walmart dino oil of viscosity recommended by the manufacturer, bargain filters by the case, and change my oil around 5000 miles.

 

The only oil related engine failure I've experienced was some failed rod and main bearings on a Buick V6 in a 1967 Jeep.  This was on a steep, long hill climb with extended high rpms, and oil starvation was probably the culprit, rather than lack of oil pressure, per se.

 

For those that are dealing with climate extremes, I can see the need for a specialized oil.  Otherwise, I don't get to wrapped up about it.  I've rolled hundreds of thousands of miles with this philosophy, if it ain't broke, don't fix it.  My 2 cents.