Race engine oil viscosity

Not to start a keyboard war but I’m curious as to what viscosity everyone runs in their race car and why. I’ve been involved in some discussions related to rpm, engine water temp, fuel preferences, 1/8 mile vs 1/4 mile, cold starts, outside air temp and so on. The discussion started relating to cold starts and how hard it may be on the engine with a 20/50 oil and oil system components, also gas vs alcohol related to water temp, and of course the hp differences related to viscosity…what say the masses…

10W-30 for me. I want it to flow quickly as soon as possible.
If the car has sat for a length of time, I plug in the pan heater, though the car has never seen temps under the high 40s.
I never have oil pressure or bearing problems.

[quote=RapidusMaximus]Not to start a keyboard war but I’m curious as to what viscosity everyone runs in their race car and why. I’ve been involved in some discussions related to rpm, engine water temp, fuel preferences, 1/8 mile vs 1/4 mile, cold starts, outside air temp and so on. The discussion started relating to cold starts and how hard it may be on the engine with a 20/50 oil and oil system components, also gas vs alcohol related to water temp, and of course the hp differences related to viscosity…what say the masses… [/quot

About the only thing that matters in terms of viscosity for race engines is bearing clearance. Typically race engines only operate in warmer temps and the engines are usually up to temp before max power is applied so that leaves bearing clearances as the primary issue. Modern engine design has trended towards tighter clearances and lighter oil for awhile now. Lots of "high tech" motors are using 0 weight oils. Old school guys still go with wider clearances and heavy oils.

I like and use 5w20W straight petroleum based Valvoline oil in all my street builds under 650 HP, all out drag race motors or HP street motors over 650 HP I use Valvoline VR10w30wt racing oil, I quit using 20w50 and 10w40 Wt. years ago after testing them on a series of engine dyno tests.
As AndyF mentioned oil does two things in our motors, it lubricates and cools, 5W20 weight will start doing its job a lot sooner, building and flowing under pressure, than thicker mixes will

Been running 10w30 for some time on Methanol and double entry. As stated before bearing clearance should dictate this. No reason to sling molasses when near water can do the trick.

I run gasoline. 2.200" rod .0028" clearance. 2.75" mains .0030" clearance. 5w25 JR1 synthetic. Oil temp generally stays about 150 at the end of the run. Back to back may get towards 190. My feeling is it is impossible to be to thin for cold starts.
Doug

I still go w/ the old school train of thought b/c it's served me well. I use 20w50 in my hemi b/c the clearances are on the loose side. Same w/ my 440.
My BB chevy is a little tighter, so it gets 10w30.
All using Valvoline VR1 conventional race oil.

In my drag race engine, I started using 10W-30 maybe 15 years ago. That engine had an oil temperature sensor in the pan, and it was hard to get heat in the oil. Even once the water temp was 170, the oil temp was cold. It did heat up some during the run, but never got "hot" and since it was shut off and waiting for the next round, the oil in the pan got cold again. Water temp and oil temp were very different in an engine that does not run for long. Street driven was a completely different story.

I found that 10W-30 produced less ET variation in the later rounds when there was less time between rounds. Compared to the 10W-40 I used to run.

Interesting, any concerns about methanol thinning the 10/30 too much? Do you run a vacuum pump? How much water/oil/ methanol do you get into your catch tank? Thanks

Spot on! it's hard to get the oil at a good operating temp in a drag engine application. And nearly impossible to 'overtemp' the oil unless something is going wrong.

GM recommends Mobil 1 0w-50 for their 632 crate engines. The owner is used to running 20w-50 in his race engines. I tell the guy to run what the GM engineers tell him to run but he isn't super comfortable with it.

A joke: the 1st number in a multi-viscosity, or the only number in single viscosity is the time in seconds it takes when cranking a cold engine for oil pressure to reach the last connecting rod.
20W50: 20 seconds.

That's what I have been running for a few years now. I run alky. If a lot of racers installed oil temp gauges and actually seen how hot the oil really gets they wouldn't be running syrup for oil.

I ran an oil temp sensor in my Duster. It takes a long time for oil to heat up. Usually takes about 10 miles of driving before oil is up to temp. Oil doesn't get warm in the pits or driving to the staging lanes.

What was the oil temp when it finally came up and stabilized?

Just comes down to every build is different. When I ran the cast crank/filled stock block with the diaper. It had a lot of bearing clearance (.0035 on mains), and with the filled block/diaper the oil would run hot.

After the first pass of the day it was always in the 180+ range, and that was with an oil cooler on the car.

I found when I tried thin oil the oil pressure would be uncomfortably low, so it always had thick syrup in it for those reasons.

Depends on the load and ambient. Driving around town oil temp is 150 to 180 depending on air temp. Freeway usually 180. Climbing a long hill or hammering on the engine for more than a minute spikes the oil temp pretty quickly.

Clearances weren't mentioned in the OP and that'd critical in the decision making.

Yeah, didn’t mention clearances mainly because I figured most race engine builders shoot for close to the relatively same clearances .002-.004 but I may be off base, I kinda assumed that anyway , it’s a really good point, I’m not smart enough to go down the rabbit hole of bearing clearances and viscosity relationships…lol

Thank you. One more if you don’t mind. When the temp went up with load, did it come back down to where it was or did it stay up where it was when the load was the greatest? Also, if it came down about how long did it take?

I snuck two in there.

TIA

Valve spring pressures and idle RPM can have a lot to do with how soon and how hot the oil temps will get, especially when warming the motors up on a engine dyno

I broke mine in on 20w-50 brad penn but oil pressure was pretty high.

1150 idle, 49psi

2000rpm 70psi

7600rpm 78psi

(I think it was just going through the bypass pretty early)

I've since switched to Royal Purple XPR 5w-30 and will dyno again soon.

Not even close.
Doug

Same here, it takes time for oil temp to warm up. I see mostly between 180-220 temps on the street depending on ambient/engine temp and load and it takes a little while to get it there.

Thing is...I am told the zinc/phos/wear additives are designed to do their thing when the oil is at operating temp.

Or in other words they are pretty much along for the ride till that time.

If your bearing clearances and sizes support it, lighter weight oil is free horsepower.

I have run into issues on OEM stuff where if the journal area is marginal for the load on the bearings, that heavier viscosity oil when at temp is needed to keep the bottom end safe. That's one of the reasons why a bunch of new cars require oils with a wide spread, like 0w40 or 5w50.

I run 15w50 Mobil 1 in my motor because it's cheap at Wal Mart and has enough zinc for flat tappet cams. I'd prefer a 5 or 10w40 for cold starts since mine is mostly a street car, but my wallet prefers the 15w50. lol

Mine only shows oil temp before the run on back to back runs. But it will make it to 150 at the end of just about any run. My clearances are out of the normal range for thicker oils either. With some warm up it'll run its number right off the bat. Very important on mornings without a time trial.
Doug

I warm mine up to 150 before I make a pass. I have a gas primer so I can build heat quickly without wasting alky. Last year double entered running the guts out of it sometimes the oil would get close to 200. I run an engine oil cooler since I have a tall fill.

Perhaps you didn't notice the first word, "joke".
What does "not even close" mean to humor?

Oil temperature tracks load, not water temperature or minutes of operation.

Power: cold water & hot oil.

We find generally an oils viscosity is pretty stable from 215-250. I wouldn't have any issue starting a run at 210 or so *f using ANY type of oil. Synthetics tolerate 40 or so degrees more before critically degrading, conventional oils will coke about 275F

This.

From Stockers to Pro Stock. Fastest way is pre-heat the oil. Come out of the lanes cold. You have to tune for that. We're using gauges to measure down to 60 degrees water temp.

Brackets, .90, dial in consistency - warm it up. Keep the temp swing from first round to the final to a minimum.

10w30 is for bracket cars. Class cars go thinner. Haven't had a quart of 20w50 in my shop for decades. Stopped using dino oil too. Made a difference

Eliminating internal leaks and unnecessary oil flying everywhere except to the crank is part of doing that. Some builders tighten clearances in the bottom end as well.

Better oils than what we had years ago also helps

Nope missed it completely. That response did sound strange coming from you. Must have read it after the bar . On vacation in Key West, lol
Doug

Am I the only one who has an oil pan heater? Roll car out of trailer, plug in heater, wait 30 mins, start car when oil gets to 160.

Joe

Nope. We have cars with heaters on the pan, accusump and trans pan. And I'm gonna put one on the rear when I get a chance.

Cheap ET.

when you say the oils are better today than back then, does that mean the pennzoil 60wt racing oil in the cardboard cans i have is not to be used ?

FWIW in the Vette we run 0 weight oil...Bearings have been in the car for the last 5 years. In my bracket junk we use 5w20

for whatever this is worth, my brother inherited a buick from his mother-in-law years ago when she passed.
he drove it a bunch of miles using 10-30, changed oil and filter religiously, and it ran like a top.
after it topped 130k or so, he figured it was getting a little worn, so he put in the same brand oil he had been using before, but this time, 10-40.
upon fire up, it had lifter noise it never had before. as there was nothing on the dash except an idiot light, he had no idea what the pressure was.
he drove it for a week or two, and it still had the noise.
he dumped the 10-40 and went back to 10-30, and the noise was gone ! lesson learned. he used 10-30 until he wore the car out, and no more noise.

Does anyone run a oil pan surface heater with a diaper???

I just use 10W30 conventional in everything except my Diesel. I use 15W40 Rotella.

I thought about it. I have one. But didn't know how it would do with the padding.
Doug

As mentioned, it is all about how your engine is setup. Old school loose clearances thick oil. One main reason for the loose clearances is a stock block was designed for what, 400HP and we build them to 700HP the block moves around during hard loads. Loose clearances absorb this deflection. I use 20W50 VR1 for years in my race car. Modern engine good stiff block tighter clearances 10W 30 or thinner. Almost all of my builds for street engines get 10w30 Lot of hydraulic roller lifters now will not work correctly with oil thicker than 10w30.

Maybe in blown alcohol or fuel, or an old shovelhead.

I run 5W-20 when index racing (B-Gas) and I run 0W when running N/A 10.5. I use Maxima Racing oils and have had awesome luck with it.

Goodness gracious that’s a beautiful car Are you on methanol or gas?

Gas

https://drivenracingoil.com/rt-5996-catalog.html

Download the catalog and find their chart on viscosity recommendations. I attached a photo as well. The section on viscosity recommendation also explains about running alcohol and how to choose a viscosity right for your engine.

I am not anywhere near as smart as they are but the best way to deal with fuel dilution on a E85 or Alky setup is #1 work on your tune so it doesn't milk the oil, #2 run the proper crankcase evacuation AKA a vac pump so what moisture is created is removed and #3 run your engine hot enough to help with evaporation of the moisture so the pump can remove it.

Nothing good ever comes from diluted oil.

I have been using 20W 50 and I believe that is why I am wearing down my bronze gear so quickly

I plan on switching to 10w30