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Low oil pressure at idle, fine when driving


mixedgrip
12-22-2006, 10:42 PM
My son's 1994 Rodeo is showing aprox. 4-5 lbs of pressure at idle which then goes to a normal pressure between 45-60 lbs when driving. Is that normal?

I have a 1996 Rodeo and the pressure stays close to 60 no matter what. I think the lowest I have seen mine go was about 30. Any thoughts out there?

Thanks,

Jim

Ramblin Fever
12-23-2006, 04:00 AM
Are you guys using the same oil/weight & filters?

mixedgrip
12-26-2006, 09:56 PM
I'm not sure. I will check with him. Would that be a cause for the difference?

Jim

Ramblin Fever
12-27-2006, 12:12 AM
Definitely.

For example, in the summer I tend to run a 5w-40 oil, whereas in the winter I run a mixture of 5w-30 oil - with the same Napa Gold filter.

My idle pressure in the summer is quite a bit higher then in the winter; even after having done a 1k mile strictly all highway stretch at 55-70mph, ranging from 2-4k rpm's - and my idle psi is more stable. My idle psi in summer is usually 35-40psi, at full speed (55-70), it goes up to 80-85psi.

Whereas in the winter, my idle psi stays right around 55psi or so, but once the engine really warms up, the idle psi drops to barely 10 or so. At speed it goes back up to 60-75psi, though, so I don't worry too much about it.

But it fluctuates more with the lighter weight oil then with the heavier; and sometimes I'll be sitting at a light swearing the oil idiot light was gonna flash at any time, but the slightest amount of gas brings the psi right back up.

Some have stated that you have more oil flowing through all the crevices with the lighter weight oil, thus less psi and better lubrication; however, I have also heard of idle psi being too low and causing the oil light to come on. There is a happy medium.

FWIW though, the oil psi gauge on these trucks are not exact, but they give somewhat of an idea.

Different brands of oil filters can do it too, but it's generally the differences in viscosities as well as oil brands.

Also, how many miles on either engine? And there ARE some slight differences in those engines as well, for instance, the 94 Rodeo has the 3.2L sohc w/175hp; your '96 Rodeo (same as mine) has the 3.2L sohc w/190hp - there may be slight differences in pressure with the set-up.

mixedgrip
12-27-2006, 10:51 AM
Thanks for the help. It will ease his mind. Everything you said makes sense. I just never thought of it in that way before. We ended up with three Rodeo's. Didn't plan it that way.

I bought my 96 in 2000. My wife was driving a Malibu which was totaled when she was rear ended. She said she wanted a CRV, like her sister but when she test drove several, in both body styles she decided to try somethin else. After it was all over she had a 2003 Rodeo.

The my son found a good deal on his 94. I looked a out at our driveway and had to laugh. We refer to it as Rodeo Drive now.

Anyway, thanks for your help.

Jim

Ramblin Fever
12-27-2006, 03:46 PM
That's cool - to own 3 of them!

I had 2 Rodeo's at one time, a '91 & current '97 - was great actually; we used to get strangest looks at passerby's. Had a little bit of everything actually & all at one time, I think that's why we got lookers.

So did you find out what oil viscosity & oil filters are in either Rodeo?

I can't say 100% if that's the reason for your son's low oil pressure though - you didn't say how many miles were on either truck?

stanger42
12-28-2006, 05:59 PM
'94 Rodeo
3.2L
4WD
Just passed the 140K mile mark.

My oil pressure is exactly as described as above as well. At idle, when cold, the pressure is steady but once it warms up the pressure drops fairly significantly (sometimes gauge looks like it reads about zero but oil light has never come on. I know the light works because it came on the first time my alternator died on me) but always raises again when I give her a little gas. It's fine when cruising. Could it just be a quirk of the '94 model?

After oil changes it raises up to what I consider normal and stays a little more steady.

Ramblin Fever
12-28-2006, 07:42 PM
Don't know what you mean by "quirk" - could be perfectly normal. But, you didn't say either what oil viscosity or oil filter you're using.

Also, how often are you changing your oil?

stanger42
12-28-2006, 08:32 PM
I was using 10W-40 until I read on this forum somewhere that a thinner oil could help with my valve noise. Now I use 5W-30 and the NAPA filter... I think it's NAPA Gold but I am not 100% sure.

I change the oil every 3-3500 miles.

Ramblin Fever
12-28-2006, 08:52 PM
Ok, yeah, with a 5w-30 oil it is normal to have a lower idle psi as long as your psi moves up when you're on the gas. As your oil gets past 1-2k miles, it thins out a bit, so this explains why thru-out the OCI your idle psi gets a bit lower.

Again, this gauge is not exact though. Sounds like you're ok - has the ticking sound improved?

mixedgrip
12-30-2006, 01:19 PM
Sorry for the delay in responding to your question but I haven't seen my son much to ask about his oil. Holiday business and all.

Anyway, he is using 10W-30 and I am using 5W-30. We both have about 150,000 miles on our vehicles. I am using Valvoline and I think he was, as well. I forgot to ask him about the brand.

Based upon what you are saying mine should have the lower pressure indication but it is his vehicle that started this thread. Anyway it seems to run fine. Maybe it's a 94 thing like someone else mentioned.

Thanks for all the input.

Jim

Ramblin Fever
12-30-2006, 02:20 PM
Could just be differences in gauge as well - is the oil gauge on the '94 EXACTLY like the gauge on the '96-'97?

I know my '91 Rodeo's oil gauge was completely different then my '97.

Otherwise, sounds fine to me as long as it's not overly loud in ticking/tapping, and the psi comes up when driving.

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