OK, the car is an 88 IROC with LB9. It has about 140k miles, but it runs great, no noises. I run M1 5W-30 oil in it, and a K&N oil filter. When I first start it up, the oil pressure gauge is pinned at the top of the scale. Once it warms up and the oil thins a bit, the reading comes down a little, but is still near the top of the scale. Once warm, the idle oil pressure is about the middle of the scale. Is this normal? It seems kinda high to me. Is my sender f-ed up? BTW, where is the oil pressure sender? Thanks!!

 

He-he.....don't know if its' normal, but my '89 'Bird has been doing that since I bought it 3 years ago.

I assume its' a sender problem.....but I don't know. At least I know it has oil pressure!

 

The oil pressure sender will either be right next to the distributor or right above the oil filter.
My LG4 always had a fairly high oil pressure, until I did the head gaskets. Cleaning out all the sludge and flushing the oil a couple of times seems to have brought it down a little. Maybe yours could do with a flush too?

Si

 

Well, I guess with 140k it should have some sludge, but I am the original owner, and I have been fanatical about oil changes, use good oil and filters, for it's entire life. I would hope it would not have much sludge since I have tried to keep it clean and healthy.

Maybe it is time for some Auto-Rx or Seafoam.

 

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The fluxuation in oil press when cold compared to when hot is perfectly normal.

 

it's normal i would put any time or effort into changing the sender. 10psi per 1000rpm is acceptable

 

5-30 is a little light on the base stock for a V-8 engine. What you describe as was previously said is normal, oil changes viscosity the hotter it gets. Depending on the age of the oil as time goes on it will lose viscosity retention. M-1 is a good oil for retention so the pressure may stay a bit higher. It you have noticed a change in the guage reading over time, it could be the sender is off a tad. With 5-30 in my engine when it really heats up at idle it's down on the first line above the red zone, with 10-30 it stays a little more towards the middle. Try a stock oil filter next change, see where it is then.

 

how long ago did you start to run m1? when i switched over with 70,000 miles in my rustang my oil pressure went through the roof after 1000 miles. it seems it cleaned the crap out of the engine and clogged the oil filter. 2 oil changes later with m1 and it runs like a dream. i actually think it added horsepower because of the less friction.

 

Woah, lots of answers to give.

1. - I've been running M1 for several years. It's nothing recent. And I believe the car's owner manual calls for 5W-30 oil, so I'm running what Chevy says to run. This high pressure issue started about a year ago. I know that oil thins as it warms, I've always seen that, but I was wondering why the gauge is pegged at the top when I start it up cold, it didn't used to go *that* high.

2. - Re Auto-Rx, I read about that stuff and some other stuff called "Nutria" or some such over on the "Bob is the oil guy" web site. That site contains lots of info about motor oils, oil filters, air filters, what sux, what's good, etc.... I learned NOT to use Fram filters courtesy of those guys. Anyway, guys there use the Auto-Rx to flush the crap out of their engines. Seems like you put the stuff in, run it for a while, then drain it out and change the oil and filter. You then fill with a "rinse" oil and filter, run it a while longer to rinse the engine's innards, then do another complete oil change. Hummm.....

I know that the M1 synth oil is a bit thin, and yet my indicated oil pressure has crept up over time. I'm starting to suspect the sender. Well, as the other guy pointed out, at least I know that I have oil pressure.

Last time I had the shop tune the car up (about a year ago), the mechanic said they ran some special cleaner through it. I inquired about what they used, and he said it was some special mechanics only stuff that they put in the gas, in the crankcase, and pour some down it's throat while running. That sounds like Seafoam. Putting some in the gas and some in the oil is straightforward, but where yould you dump it in to do the down the throat while running trick? You'd want it to go into all the cylinders, so you'd need to get it into the upper plenum somehow. Ideas?

 

Yes, GM and everybody else recommends 5-30. It's a fuel efficiency issue. 10-30 is preferred by most dealer mechanics unless you live in Caribou Maine. A fully pegged guage when it's cold is normal, as I said with 5-30 after it's really hot it takes a big nosedive. The only reason I mentioned the filter was once when I was travelling I sent my wife to get the oil changed on the IROC, never is mileage, strictly time. They put what I call a "white box special filter on". The oil pressure remained unusually high all the time. Don't know if it was the filter media, or a problem with the filters bypass pressure but i got rid of it quick and went back the the Delco filter. Everything went back to normal. Remember, no matter what they say the lower the particulate filtration capability the more resistance to oil flow. The sender is cheap enough to replace, but get an AC Delco one. it will be more accurate than aftermarket.

 

Sounds like normal sludge buildup. Theres not much you can do about it. Sometimes the flushes help and sometimes they dont. I wouldnt worry to much about it as long as the engine continues to run good.

 

Yep, that's absolutely normal. Cold oil is thicker, hence higher pressure when cold. Mine does exactly the same thing, I'm running 10w30 in the winter. IN the summer it's 20w50, (125K on the car) and it never goes under 45psi, and its PEGGED when cold. Don't worry about it, W.A.D.