I have a 91 RS with a TBI 305. Usually the car runs with around 45 psi of oil pressure. Yesterday when I was driving to work I looked at the gauge and it read 15 psi and when I came to a stop it read zero. The car is full of oil and runs fine and makes no unusual noises. My buddies dad thinks that one the bearings are about to go. Could it be a possible gauge problem or could my car be ready to die. If anyone has had a similar problem or has any ideas I would appreciate it.

 

could be the oil pressure sending unit is bad. cheap repair, but you should check the acutal oil pressure first.

 

Let me guess you are running a Fram oil filter? If so change it out to a Napa gold or a wix filter and you will be fine. Fram is bad about clogging up and not letting oil flow. I went through this on my Nova not long ago. I change it to a Napa gold oil filter and not had a problem since. The Fram filter was on for less than 3 weeks. The Napa gold filter has been on for 4 months.

 

change the filter, then check the in-dash gauge, if it reads low, turn it off until you can connect a mechanical gauge. If that shows good, it's your sending unit. this is a common problem.

 

ok heres an update. I changed the filter and saw no change. So I replaced the unit down by the filter and now I get a reading of 15psi at idle and 25-30psi at crusing speeds. my question now is that too low of oil pressure for a 305 with 162k miles on it and is it safe to drive that way if I need to.

 

15 at idle is a little low but you'll be fine. is 30psi at cruising when warm? What does it read at idle when cold (sitting overnight)? What oil are you running? Try hooking up a mechanical gauge to verify that there is nothing wrong with the factory gauge as well. If it is still 15psi at idle on the mechanical gauge (again check it cold as well) just keep an eye on it. Did you change the oil when you changed the filter? What filter? If you didn't change the oil when was the last time it was changed? Sorry for all the questions, just trying to get a better picture of the whole scenario here to help you out.

 

A stock or even a little over stock only needs 10 psi for every thousand(1000) rpms. So if you idle at 750 rpms you only need 7.5 psi. If you are turning your engine 7000 rpms then you need 70 psi at the 7000.

 

^ Yes but dropping 15psi with no other changes is cause to check things out IMO. 15psi is fine if that's the true reading. Just keep the oil clean/filtered and keep an eye on the gauge in case it's signs of a failing pump or bearing.

 

It is running 30psi after it has warmed up. The car hasn't completly cooled off since I replaced the sensor so I will get back with cold idle. I am using 5w-30 mobile that comes in bulk at the dealer I work at. (Its a Honda/Acura). The oil was last changed about 1500 miles ago and gets changed every 3-3700K miles. I did not change the oil today when I changed the filter and I put on a Napa pro gold filter. I had been using the bottom line Napa pro select filters. I still need to get a hold of a mechanical gauge to check the reading.

 

Let us know what it reads after you start it cold. If you can, change the oil, won't hurt doing it a bit early. You should be fine as long as it doesn't keep going down.

 

the oil is thin run 10 30 and watch your psi come up to or close to normal numbers

 

5-30 is too thin for a motor designed for 10-30 anyway, then you throw in increased bearing clearances due to wear and such. thicker oil is needed.

 

10-30 and 5-30 have the same "weight", but the thermal properties are different. The cold start viscosity is different.

"SAE viscosity gradings include the following: 0, 5, 10, 15, 20, 25, 30, 40, 50 or 60. Some of the numbers can be suffixed with the letter W, designating their "winter" (not "weight") or cold-start viscosity, at lower temperature. The document SAE J300 defines the viscosimetrics related to these grades."

 

and the point you are trying to make is what? i never said to run 10-30 and that will fix what ails you. i said run a thicker oil. i run 15-40 in mine, but how about 10-40, thats thicker and would maintain the manufacturers assumed winter viscosity. even with no problems right now while warm, the thinner viscosity(ie "weight") will be detrimental in the winter when its cold. to further that most hondas i've worked on recently take 5-20, so it would be simple to assume that the honda bulk oil would be 5-20 not 5-30. bottom line is that a lighter weight(or thinner) oil is never a good thing without being designed for it, then you add in a few 100k miles and looser tolerances, running thicker oil isnt such a bad idea.

 

if what you are saying is true then how come?
1 10 weight gives you higher oil psi then 5 weight
2 why do they even bother have the 2 different weights?

 

My comment wasn't directed toward you so don't take it as so. I didn't say you said anything so don't get all bent out of shape. You are correct and I never said you weren't, but 50bmgshooter said "the oil is thin run 10 30 and watch your psi come up to or close to normal numbers", I was just stating that the change in "w" number isn't really a change in "weight". ALOT of people have no idea what the "w" means and assume it means weight when actually it's winter. It was meant more as an informative post. Calm down a little bit lol. I always ran 10w-40 Castrol in my hi-po motors so I agree with you, sometimes when you live in a colder climate that is colder all year round the lighter weight is better but only in certain circumstances. I run 5w-40 in my truck, 10w-40 in the Biscayne and 5-30 in my wifes Camry (mainly because it's under warranty and I won't touch it lol, they can put whatever they want in it as long as they fix it if something goes wrong)

 

and i wasn't trying to prove you wrong or argue with you, i was just stating my opinion, and apologize if it came of as me being overly agressive. but i hear you on what people think the "w" stands for.

 

both of your questions are answered in the post you quoted. the 10 "weight" will only give better oil pressure when cold given the same warm viscosity. second question, the two weights (weight cold and weight warm) are used due to the fact that with a thick enough oil it is possible to burst filters and thats never a good thing. i run 15-40, and when cold at regular shift point i have about 75-80 psi, and is 70-75 degrees when i leave for work in the mornings. straigth weight oils are available, but not recommended for most vehicles iirc. i know that rb mopars (440s and such) are bad about bursting filters when cold with thicker oils. there are even special filters available with a higher burst point to avoid this problem.