I am debating whether or not to put 20w50 oil in my vette. I am currently running 10w30. I recently have noticed that at the hot temps my vette are reaching during the extreme temps of the day here in Dallas, my oil pressure is staying pretty low.... lower than I'd like it to be. When I start her up in the morning it's at a good 50-60psi. When it starts getting hot (within a few minutes)... the oil pressure is dropping to 40psi while driving and 10psi at idle. 10psi seems too low to me.

Do I....

a) keep running like this
b) put in 20w50 oil
c) look for problems in the engine (ie oil pump)

 

For the Phoenix area, I run 15w-50 in the summer time and 10w-30 in the winter time...I also did this when I lived in Orlando. The oil won't bring your temps way down, but it will help keep the pressure in check. 20w-50 might be a little thick...I've never used it before!

Jay

 

xxW50 oil's are the same viscosity. The numbers before the oil are the winter temps. So 15w50 and 20w50 are the same thing for hot use.

 

First, work on cooling your engine bay with cooler fan temps.

Next, I ran 20W50 on my L98 from 100,000 on. It always had plenty of oil pressure. When we took it down for the rebuild, the builder said it looked like a 70,000 mile motor at 145K.

 

My 94 with 45k has similiar pressure readings as yours. I am using Mobil 1 5w30. I also see the same pressure in my truck and I am going to switch back to 10w30. I would not use 20w50 or a non synthetic oil.

[This message has been edited by eusdji (edited 07-23-2001).]

 

There is NO difference between 5W30 and 10W30 above 32 degrees F.

 

When you see 10W-30 on a quart of oil, it means that it acts like 10 weight oil when it is cold (the "W" means winter, say -10^C), but acts like 30 weight oil when hot (100^C not 32 F air temp.). This is not to say that it is actually thicker when it is hot. Hot 30 weight oil is thinner than cold 10 weight oil. Even so, it still helps provide the benefits of both types of oil depending on its temperature. So 0W-30 oil acts like 0 weight oil when cold, but maintains a 30 weight viscosity when hot. Think of it this way: when your engine is hot, there is basically no difference between 0W-30, 5W-30, and 10W-30 oil. They are all acting like 30 weight oil at this point. It's at cold startup, when almost all engine wear occurs, that the viscosity is different. The 0 weight oil will get to the engine components quicker than the 10 weight oil, but in reality cold 0 weight oil is still thicker than hot 30 weight oil. On the other hand when the engine is cold, there is no difference between 10W-30 and 10W-40 oil. However when the engine is hot, the 10W-40 oil is thicker than the 10W-30.
Here is a Engine Oil Choice site:
http://members.nbci.com/minimopar/oil.html
I can't find the site that talks about the additives that are used in a muti grade oil but it said that the additives break down faster then the oil so the smaller the gap between the viscosity the better. If I find it i will post it.

 

A good rule of thumb is 10 psi for every 1,000 RPM. Although you are not comfortable with the pressures, they appear to be within the acceptable range. Check your manual, they usually don't allow the use of an oil with a high VI, i.e., large range between the low and high number.

 

I was thinking the same question but then the other way around. Speed-o-motive suggested running in the engine with 30 weight mineral. I did. I then refreshed the oil after say 800 miles and put 15w40 mineral. From that point I saw the pressure go up from say 20 psi at idle to around 36 psi. I thought this to be to much. It would also go to 67 psi around 1800 rpm, which I thought was too soon. I want to run mobil 1 and think of doing what they want, run 20w50!!! I feel it is too thick. Probably better to run 0w30

 

There is a reason that GM never specifies 10w40. The word is that, the larger the spread between the weights ( in that case it's 30 ) the less efficeive a lubricant the iol is. Why? Because there is an additive in the oil that is not a lubricant at all. The wider the spread, the more of this viscosity modifier is in it. The modifier only serves to change the viscosity. As a lubricant, it is useless. 10W40 has a lot of this additive in it.

I have been using streight 30w Penzoil ever since I heard about that one.

Just my .02

 

10psi?ehh.. not to bad.but what it should be for a small block is about 20-22psi.my old 86 was getting down to that and then later on ...beyond like 5 or 7! so i had the oil pressure switch changed,now its back up there to where its supposed to be 20-25psi(when hot)IMHO