93BlackT/A

I am trying to figure out what type of oil viscosity I should run in my car or if I'm already running it. I'm running a C5R if that means anything. Also how do you figure what viscosity you need to run?

Thanks

1989GTA

Is this a stock factory motor? What part of the country do you live in?

JRL 31x

10w-30 for life.

.boB

iTrader: (1)

You need enough viscosity to maintain proper pressure in all situations. More is not better. Thicker oil is less efficient, and takes more energy to move around.

5W-30 is just about perfect for most modern engines.

96capricemgr

iTrader: (1)

Pressure is NOT what matters to the engine, we just watch pressure because it allows us to see deviation from normal.

Far as weight you will have folks who don't understand viscosity tell you things like 5w-30 was GM spec so use that. Reality is OEMs have a lot of concerns that are NOT about engine life, and that the "30" part is a range, one 0w-30 is thicker at operating temp than another 10w-30 and a year later as formulas change the 10w-30 might endup thicker.
If you want to worry about viscosity alone any 0w, 10w, 5w-30 or even 40 is going to do the job and picking between viscosities and brands beyond that is pretty much splitting hairs.

Someone wants to argue that please put up the UOA results.

wayland1985

From what I've heard, it's less about viscosity and more about zinc content, especially with the higher spring pressures many people are using with their cams.

93BlackT/A

No. C5-R race block.

93BlackT/A

I contacted finish line performance and they recommended 20w-50. That's what they run in their C5-R motors. Out of curiosity I also contacted Pratt & Miller and they concurred with running the 20W-50. They said it's what they ran when they used that block.

vettenuts

iTrader: (4)

I thought about a C5R a few years back, nice block. Do you know the bearing clearances? Also, Katech did a lot of work with that block in the C5R race car, you might want to ask them as well.

93BlackT/A

Don't know the bearing clearance since I'm not the original builder. Car is brand new to me. Good idea I will contact Katech today, why didn't I think of that. Thanks!

svede1212

iTrader: (3)

I'm in for why manufacturers don't care about engine life. . .

redtan

iTrader: (5)

First of all you should be asking the builder who put the engine togther for recommendation as they are the ones that know the clearances and what type of lubrication those need. And they will probably be the one either offering some sort of warranty or who you will be going back to in case there are any issues with the engine. So you want to follow what they say.

As a general rule of thumb, you want something thick enough and resistant to shearing at high loads that you might expect the engine to see and thin enough at cold startup that it will flow well in whatever temps the engine will see.

I personally run a 0w40 in my LS2 just because I tend to use it in really cold weather hence the first number, and also have heard and read that LS engines like slightly thicker oil especially older ones.

OEM oil recommendations are around fuel economy and not so much engine life. Most manufacturers could care less if an engine lives 100k or 200k as most likely the car will be long out of warranty by then. That's why you're starting to see oils as thin as 5w20 in mainstream cars. Alot of the hipo European cars require upwards of Xw50 or 60 oils for protection. Now obviously that depends also on the clearances built into the engine, but ultimate protection also has to do with it.

93BlackT/A

I have been trying to get ahold of the original owner that had the car built but I can not get ahold of him. He sold the car to my friend 7 years ago off of hear but he will not answer his private messages I send him. Also my friend no longer has his contact info. So in that case I'm up **** creek on knowing the bearing specs and oil he was told to run.

93BlackT/A

Contacted Katech this morning and they recommended 5w-30 for street use and 15w-50 for track.

Lingenfelter said the same pretty much but said bearing clearance plays a roll too. Grrrrr... wish I could talk with the original builder on this.

Red89GTA

FWIW some OEMs are going as thin as 0w-20 full synthetic. Mazda since 2011 in non-turbo 4 cyl, 5w-20 in v6 applications since 2003. Nissan recently went from 5w-30 to 0w-20 in some of their new 4 cyl engines too. There may be others, but that's 2 I know of.

I can't speak to how well these engines will hold up after 100k, as that's the oil they're designed around, but I know that fuel economy is a major factor. The harder it is to pump, the more fuel you use.

redtan

iTrader: (5)

They may very well make it to 100k and more, but I doubt these engines are being driven HARD like a lot of us like to do. So for a basic engine driving around town as most people do that oil is sufficient.

For hardcore car guys like us who like to have fun and drive our cars hard at the strip or track I don't think that type of oil will protect the engine enough.

LLLosingit

iTrader: (4)

You may never know what the bearing clearances are so I would consider what you do know like.
What start up temperatures will be.
What normal operating temperatures will be.
What rpms the engine will see.
What engine loads will be.

I run 10-40 in the summer in all my vehicles and 5-30 in the winter, I live in the Midwest and we see extreme swings from one season to the next. 100+ in the summer and well below 0 in the winter.
When I raced (circle track) I ran 20-50 with a zinc additive because the motor saw sustained high rpms and loads lap after lap.

redtan

iTrader: (5)

What's the reasoning for the 40 weight oil in the summer and 30 weight oil in the winter? I can see the first number being different since most likey cold startup temps will vary greatly between the seasons. But as far as operating temps, regardless of whether it's 0* or 100* outside your oil temps will run basically the same (maybe a little higher in the summer).

1989GTA

Couple of questions. What weight oil are you running now? What is your oil pressure at idle both cold and hot? What is your oil pressure at rpm with the oil hot?

I have an LS3 based 427 with slightly large bearing clearances and I was running a 5W30 oil and the oil pressure was to low for me. I changed to a 10W40 and things are much better. I am considering a 5W50 synthetic or so when the motor is broken in. I also live in Southern California so the weather does not get that cold.

96capricemgr

iTrader: (1)

Oil pressure does NOT really matter except to watch it for deviation from norm.