[PontiacLars]

I will use Vavoline VR-1 racing oil in my engine. 3" mains and 2.2" rods.
Bearing clerance .0030-.0032 mains and .0028 rods.
Valvoline has this oil in 20W50 and 5W50. I dont really like how thick
20W50 gets in the spring and fall. Any reason not to run 5W50 instead?
Sounds like a perfect compromise, but it has such a big viscocity spand that I get suspicious.

[steve25]

The bigger the viscosity spread of a given oil the more crap it has in it that plays little if any part in the oil having excellent lubrication properties and film strength..

I would run a 10w30 year round and during the Summer change the filter so you have room to add a Qt bottle of Lucus oil additive.

[Kenth]

Pontiac recommends straight 30 or 10w40 for the Ram Air engines that has the crank grinded .001" smaller than std, .0055"-.0061" piston clearance, deleted oil shields on valve springs and 3.73:1 - 4.33:1 rear gears, instead of straight 20 or 10w30 for a std engine.
No Xw50 oil ever unless you´re in Death Valley or running NASCAR.

[Jay S]

Most those 5w50 full synthetic oils were formulated for modern high performance cars. Especially German made engines, some supercharged stuff over here. From what I recall they are formulated more for those types of platforms, and run lower zinc and P for emissions equipment. Personally I think for your oil clearance the 5W serves no purpose unless your are operating it in very very cold Arctic weather. The VR1 10w30 would likely serve you better, 20w50 VR1 might be fine oil too, but really need more details about the combo. 10w30 should be fine with those oil clearances yet. This is a oil sample from a Roush 5W50 made by Valvoline, don’t know if it is exactly the same as the 5w50 your looking at, the target markets are the same though. Pretty low on some of the antiwear properties, really high anti-friction moly, with moderate detergent levels.

[PontiacLars]

I checked some oil charts and with my clerances, iron block and auto cross or street driving the recommendation was 20w50. Pure drag racing could use lighter as the oil did not get that hot.

My engine is a 4.5" stroker with roller camshaft.

[i82much]

I'm switching over to Mobile 1 0w-40 full synthetic for everything:

Hyd roller Pontiac V8
Flat tappet BBC
Flat tappet 4.0 Jeep
Hyd roller LS (6.0 vortec, L96 in my 2500HD).

The M1 0w-40 has plenty of zinc for the flat tappet cams, good cold starts, thick enough to beat on during the summer heat, and you can get it pretty cheap in the 12 quart "bag in a box" from Walmart.

I hate having a bunch of different half-empty bottles of oil of different brands and grades on the shelf, this just makes life easier.

[PontiacLars]

Bearing Oil Clearance Chart

Oil Viscosity Rod BearingClearance Main BearingClearance
20w / 5w20. < 0.0021 <0.0020
30w / 5w30 0.0021 – 0.0026 0.0020 – 0.0025
40w / 10w40 0.0026 – 0.0031 0.0025 – 0.0030
50w / 20w50 0.0031 > 0.0030 >

Found this too. Maby 10w40 is plenty thick enough.

[Jay S]

The flow characteristics change a lot between oil brands, even with the same viscosities, the chemistry is different also, no chart I know of is very accurate for uses of various oils between brands.

Road racing, street and drag engine are all different things, the oil gets darn hot on some drag engines, oil can be over 250*F by the end of the run. Especially filled blocks.

To determine proper oil weight after some usage I usually use the pressure drop after warmed up, or to much pressure warmed up full throttle, cold pressures to high or low, and heat soaked idle pressure. A racing grade 10w30 will take a lot of abuse.

[Jay S]

I have some reservations about a 0W or 5W on anything running a carburetors unless the temp is very very cold. Mostly because of fuel dilution in oil with carb set ups and cylinder washing. What do you hope to gain over 10w?

[59safaricat]

Roller rockers/lifters?

I wouldn't use an oil thinner than 10w on a flat tappet camshaft. Newer engines with roller setups can tolerate a thinner oil due to less friction. Just my 2 cents.

Looks like 10-40 fits the bill.

[Schurkey]

Thinnest oil that gives acceptable hot idle oil pressure, within reason.

GM went on a big crusade decades ago to get people away from 10W-40. This was beaten into our heads at the GM Dealership back in '84, and it wasn't "new" then, although I think it was new-ish.

The bearing has better load-carrying capacity when the oil clearance is less; and tighter clearance requires thinner oil. Thinner oil flows better when the engine is first started. It's like a three-way win. Building engines with oil clearances you could push a kitten through is obsolete, if it ever was a recommended procedure.

[Sirrotica]

If you want an informed answer/reccomendation for oil, based on application, you need to go right to the lubricant manufacturer. Every time I've had oil related questions, I've found the correct answers from the people that have engineered the oil, and additive package.

The best example was when I worked for an asphalt sealing company, in the mid 80s, that was losing air cooled engines on their parking lot blowers at the rate of roughly one a week. The engine manufacturer was reccomending 30 weight non detergent, and changing it once a week. Following that advice did not fix the problem of seized engines. I called Pennzoils tech line, explained the problem, and was told to buy their "new at that time" full synthetic 10W30 oil. This completely solved the problem, and also we were able to extend oil changes from once a week to every 3-4 weeks depending upon hours the blowers were run. The ability of the synthetic to handle the excessive temps on asphalt parking lots (up to 140 degrees), running at 3600 RPM constantly.

They've done all the testing, so you can rest assured that your engine build isn't the guinea pig doing field testing. All the major manufactures have tech lines, that are there to answer questions about their products. They know far more about their oils than average Joe, on an internet car enthusiast forum.

BTW, the oil temps encountered on autocross, road racing, or oval tracks, are much more demanding than drag racing will ever be, been there done that. I've broken engines before learning it's entirely different ball game than street, or drag racing. Oil coolers should be considered for this type of racing, and at the bare minimum, an oil temp gauge to at least monitor oil temps..

[59safaricat]

Originally Posted by Schurkey

GM went on a big crusade decades ago to get people away from 10W-40. This was beaten into our heads at the GM Dealership back in '84, and it wasn't "new" then, although I think it was new-ish.

Back in those days and even into the 90's, the viscosity index improvers in 10-40 sheared and caused sludge issues. That's not the case today with better oil technology.

[AG]

My race car has 0.0029"-0.0035" main clearances and 0.0024-0.0026" rod clearances. I use Walmart 10W-40 full syn and it has 30 psi at full heat soaked 1000 rpm idle. I have had it apart and all the bearings looked good. Oil flow is just as important as viscosity and viscosity requirements are more dependent on bearing loads. For my power level (~700 Hp) what I use is fine. I use 5W-30 full syn in my street cars.

[Sirrotica]

Originally Posted by Schurkey

Thinnest oil that gives acceptable hot idle oil pressure, within reason.

GM went on a big crusade decades ago to get people away from 10W-40. This was beaten into our heads at the GM Dealership back in '84, and it wasn't "new" then, although I think it was new-ish.

The bearing has better load-carrying capacity when the oil clearance is less; and tighter clearance requires thinner oil. Thinner oil flows better when the engine is first started. It's like a three-way win. Building engines with oil clearances you could push a kitten through is obsolete, if it ever was a recommended procedure.

I also worked in a GM dealership in the mid 80s, GM did not want customers using 10W40 oil in their engines, bulletins were issued about the subject, and confirming that the 10W40 additive package would stick rings to the pistons. I've never used 10W40 in anything since GM issued their TSBs about it.

In an engine used to closed course racing, the clearances only need to be wide enough not to restrict oil flow for the extra flow needed for cooling bearing surfaces. Widening them further serves no real purpose in a naturally aspirated, gasoline fueled engine. When the clearances get too wide, the oil wedge is more difficult to maintain with a standard oil pump. The current LS engines demonstrate that well, they don't have clearances in the .003 area. Even with high mileage factory stock bottom ends, LS engines are currently being pounded to death on race tracks everywhere.

[hojs69]

Just another data point.

5W20 for over 20 years now in a 0.030 over 455. 80 psi pump. Street strip.

Bottom end is ~ 40 years old. Numerous changes through the years; cams, heads, intakes, carbs, ignition, etc.....

[Jay S]

We have multiple old street and strip engines in cars that are 30 some years old with 10w30, 15w40, and a couple that have 20w50 in them. I have never seen the need to drop lower than 10w30. I just run 60 psi pumps though.

We ran 20w50 in the 455s in dirt track race cars. My avatar photo was a 466 CID 3.25” main Pontiac. That one would get up around 6500 at the end of the straight away on nights the track was sticky. The main feature was a 25 lap race on a 3/4 mile track, sometimes would go 40 laps a night if it had to go up thru the features. That is definitely a different kind of abuse than drag racing! Only could go a few weekends on an oil change. The first engine we did the oil clearance was pretty tight. We kept opening the oil clearance up to make the bearing last better. The last engines we did, had .0025” to 003” on the rods and .003 to 0035” on mains, and by the time the remote oil filter and oil accumulator were filled, it held about 14 quarts of 20w50. By the end of the night, the radiator would start to get plugged up with mud, and your watching it go down the track past 6000, never dropping below 4000 anywhere while it is over heating wondering how on earth it is still running.

On the flip side, I know a lot of the worry about oil weight is unfounded, and I personally would say that goes both ways with in reason… thick or thin. A good 5W20 is pretty darn tough too.. I ran into one engine with Valvoline semi synthetic 5w20 that was started on a cold day (-28*F) and the oil filter partially collapsed. After that would randomly loose oil pressure while driving. Replaced the sensors and it still did it. Shut it down and start it up and the pressure would come right back. I thought it may be an electrical issue. It was driven months like that, once it went 10 miles with no oil pressure registered at all and didn’t make a sound that indicated it had trouble. Finally it got worse, it had a oil temp gauge, so I also watched the oil temp to see if it rose. I drove 6 miles at 70 mph at 2500 RPM and nothing changed, oil pressure at zero. I thought for sure it was electrical, but mile 7 it gained 1 degree, mile 8 it gained 5* and I shut it down. I let it cool down, started it back up and it was fine again. But it started acting up right away, end up hauling it home. I changed the oil filter and we put a few thousand more miles on it. I end up overhauling it, the cam was what went bad. I got into it and found out it was a Reman engine, and someone had forgotten to put the back cam bearing in. LOL My point in mentioning that is it really isn’t that often that oil that is changed in the correct intervals is the blame for engine bearing failures.

[TransAm 474]

I would say, for your engine, a good 10w40 would work great, such as the Valvoline VR1 .... and for those that have a Flat Tappet camshaft, we also use, and have had great results with the high zinc 10w40 Lucas Classic Hot Rod oil.... anything with .0032" + bearing clearance on Mains and Rods we like a good 20w50 oil .... on our Procharger/Methanol drag race stuff with .0035" bearing clearance, we sometimes use a good straight SAE50 weight ... but we also like an excellent 20w50 race oil in that application as well, such as Brad Penn(now PennGrade)

[vertigto]

I don't recall Valvoline VR1 having a 10w-40, only 10w-30 or 20w-50 (and straight weights)? I had been using the Valvoline VR1 10w-30, but thought I'd try Driven HR5 10w-40

[Jay S]

Originally Posted by vertigto

I don't recall Valvoline VR1 having a 10w-40, only 10w-30 or 20w-50 (and straight weights)? I had been using the Valvoline VR1 10w-30, but thought I'd try Driven HR5 10w-40

I really like the 10w40 Driven HR5, especially on older flat tappet builds that have some older dried out gaskets, but on new flat tappet or roller builds also. The HR5 has some extra detergents and antiwear additives that VR1 doesn’t have, but is easy on gaskets yet, and is not a para synthetic, I think it only uses the conventional Penn based oil. VR1 doesn’t have a very strong detergent package, you need to be on top of the oil changes in street cars. The full synthetic Driven GT1 seems to be very high on detergents, I think too strong, some builds have trouble sealing up with it. HR5 is engineered for our old cars.

Closest you could come with VR1 is to 50/50 mix the semi synthetic VR1 10w30 and 20w50 and end up with a 15w40 VR1. Which Valvoline reps says you can add any of their VR1 products with each other.