TraviZ

iTrader: (2)

What oil weight should I run in my iroc?

I started with a thick 20-50 race oil and my pressure started at 80psi, and never went lower then 60 hot. i figured this is way too thick so I dumped it out and now tried 5-30, its a good 60 cold, and when its hot, cruising is around 30psi and maybe lowest ive seen is 25 at idle..

should I try something else, im not too familiar with oil weights, and what should be used in such a custom engine as mine.

TraviZ

iTrader: (2)

im thinking of trying a 5-40 next time, to keep up the pressure a bit when it warms up...

radical82

Higher Viscosity (thicker) oils put more strain on the oil pump and oil pump drive shaft then lower viscosity oils, the final result being that higher viscosity oil has greater parasitic horsepower loss then lower viscosty oils. The old rule of thumb for oil pressure was 10 PSI for every 1,000 RPM. Going by this a typical 2500 RPM cruise should have 25 PSI for good lubrication and minimal horsepower loss. Then, on a full power pass at the digs going through the traps at 7,000 RPM you would need 75 PSI.
One variable to this old rule of thumb is of course bearing clearances throughout the engine...

Then, throw in the synthetic oils like many of us run and you will get better lubrication with looser clearances bringing about less reciprocating resistance and higher performance....and after this it gets really difficult!!!!! Might want to check with one of the oil companies tech departments if you really want to get educated on engine oils and lubrication requirements in general. Both Mobil 1 and Quaker State have excellent web sites and get very detailed on explaining oils and what is best for a particular application.

Quick answer, your pressure with the 5-30 is adequate if you're not pounding on the car everytime you're in it. 10-40 would probably increase the pressure moderately, but if you don't need the added lubrication, why give up the parisitic horsepower loss, minimal as it may be.

TraviZ

iTrader: (2)

the thing is, i am always pounding on this car, thats why i built it.
so, a bit thicker seems good.
20-50 was too thick i think, i didnt want to starve my cam bearings or valvetrain any.

radical82

Lack of pressure wouldn't be the problem, lack of volume can be just as terminal as lack of pressure....What do you have for an oiling system?????

UnderCover89TBI

iTrader: (25)

15-40 delo has more lubricating components in it. I run a 10-30 synthetic in mine

OUTATIME GTA

iTrader: (2)

Ditto. Sometimes a 5-30 on the DD. I never really knew what applications would really benefit from the higher viscosity oils. I just assumed tractors or something, haha.

STEWARDORNG

I use to always run 20-50w oil thinking it was the way to go then I met Warren Johnson at an event and he said he would run the thinist oil he could get to stay in the motor of course this is to get the most horse power. I am sure you change your oil as often as I do so standard 5-30w should be fine.

kairles

iTrader: (2)

What was the clearance when you put the motor together? If it was tight(stock) then 5w30/10w30 should be fine, if you set it up on the loose side then you'd want to run something thicker

TraviZ

iTrader: (2)

Ya Terrell i know that, but is there a formula like x ammount of bearing clearance = this weight oil?

vindeezl

iTrader: (2)

20w-50 I use in old high mileage crap...

You need 5w-30, I broke in on GTX then ran Mobil1 Synthetic 5w-30 in my 355 religiously.

JesasaurusRex

iTrader: (3)

UnderCover89TBI

iTrader: (25)

10-30 til 80k miles then 10-40. Be just fine

Apeiron

No

UnderCover89TBI

iTrader: (25)

I know the real low viscosity oils were designed because a lot of newer cars have aluminum blocks and aluminum expands more than cast. So therefore it needs thinner oil to flow properly still. most fords and honda's run 5-20. Ive seen some other foreign cars run a 0-20....

dannyboyemt

Here are some REAL time, as well as, laboratory tested "ultimate" and unchangeable truths:

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