Autocross/Hillclimb Oil Article

[cody]

I read both articles at this link, but the one in the sidebar is far more insightful the other.

Autocross Oil?

Autocross and hillclimb racers have their own issues with oil heat, but it’s at the other end of the temperature spectrum. In these types of competitive driving, too little heat becomes the problem, not too much.

Unfortunately, a lot of autocrossers and hillclimbers choose oils that make the situation worse. Many of them campaign modified cars and assume that their radical engines justify the use of a thicker oil. Where the spec for the stock engine is 10W40 or even 5W30, they’ll go with 20W50.

They’re missing a crucial piece of the puzzle. Most autocross and hillclimb cars roll to the starting line with cold oil: Not quite freezing temps, but far from the 212 degree mark. The 20W50 oil is likely to behave closer to its 50-weight rating in these conditions, so it’s doing precious little in the way of lubrication. The thick oil isn’t able to penetrate deep into the engine, and the results can include spun bearings and thrown rods. A popular follow-up move by too many enthusiasts in this situation? An even thicker oil, which only exacerbates the problem.

Most autocross and hillclimb cars—even those that have been modified—will be happy with the oil viscosity recommended by the manufacturer. Before hitting the gas, get the oil up to temperature so it can do its job. If there’s topnotch oil in the sump, autocrossing simply won’t wear out the engine.

A technically savvy driver with a good oil temperature gauge can experiment with slightly lighter oils. These will get up to temperature quicker than heavier oils while offering more power, yet still protect the engine under these unique conditions.

[Ms Heatha]

So...If I was looking at doing a hillclimb this summer out by Arcada, Id be ok with my 5W-30 right?

[cody]

IMHO, pretty much any situation except driving at the track in hot weather or towing something heavy, 5W-30 is fine, especially if it's a quality full synthetic.

Remember, the lower number is the weight that the oil acts like when it's cold and the higher number is what it acts like when it's hot. These qualities allow an oil to maintain the proper viscosity in a range of conditions.

I just bought some Rotella T 5W-40. The 5 means that the oil will be thin enough to circulate when cold, just as thin as the manufacturer intended. However, the 40 means that it will maintain composure (film strength, viscosity, etc) better when hot.

The fact that it's a great synthetic (gets great UOA's/reviews in Subaru's) is the main reason I bought it though. And it's $5/quart at the Pepboys where I buy my Purolator Pure1 Oil Filters.

That's my thinking anyway. Hopefully I'm not wrong. I was just reading the back of the jug and it says it's "suitable for" tractors, pickups and big rigs.

[cody]

Originally Posted by cody

I read both articles at this link, but the one in the sidebar is far more insightful the other.

I just reread the article and it's wrong.

Most autocross and hillclimb cars roll to the starting line with cold oil: Not quite freezing temps, but far from the 212 degree mark. The 20W50 oil is likely to behave closer to its 50-weight rating in these conditions, so it’s doing precious little in the way of lubrication. The thick oil isn’t able to penetrate deep into the engine, and the results can include spun bearings and thrown rods.

pretty much directly contradicts

Multi-weight oils (such as 10W-30) are a new invention made possible by adding polymers to oil. The polymers allow the oil to have different weights at different temperatures. The first number indicates the viscosity of the oil at a cold temperature, while the second number indicates the viscosity at operating temperature. This page from the Sci.Electronics.Repair FAQ offers the following very interesting description of how the polymers work:

At cold temperatures, the polymers are coiled up and allow the oil to flow as their low numbers indicate. As the oil warms up, the polymers begin to unwind into long chains that prevent the oil from thinning as much as it normally would. The result is that at 100 degrees C, the oil has thinned only as much as the higher viscosity number indicates. Another way of looking at multi-vis oils is to think of a 20W-50 as a 20 weight oil that will not thin more than a 50 weight would when hot.

http://auto.howstuffworks.com/fuel-e...estion1641.htm

[sperry]

I guess I should have read your other post more carefully. Oil weight is written like "5W-30", which I learned to think of like "5 Winter (the cold viscosity) dash 30 (the hot viscosity)".

But the article is still correct in that 20W oil is going to be bad for a motor that expects 5W or 0W when it's cold. Like they said, racers tend to use heavier oil to fight the viscosity breakdown that happens when you over temp the oil. Since that's not happening at autocross, there's no gain for using the thicker oil.

I think your logic for the 5W-40 makes sense. 5W is going to be close to (exactly?) the factory recommended cold weight, while the 40 should afford a little extra protection on hot days when running hard, at a small expense of fuel mileage and horsepower. I just wouldn't bother with using non-factory recommended oil weights unless you are in fact running the car hard in the hot. 5W-40 probably won't make a huge difference, but running 15W-50 or something in a street car that never really gets super hot oil temps is probably going to accelerate wear on the motor over the 0W-30/5W-30 factory spec oil.

[cody]

Originally Posted by sperry

I guess I should have read your other post more carefully. Oil weight is written like "5W-30", which I learned to think of like "5 Winter (the cold viscosity) dash 30 (the hot viscosity)".

But the article is still correct in that 20W oil is going to be bad for a motor that expects 5W or 0W when it's cold. Like they said, racers tend to use heavier oil to fight the viscosity breakdown that happens when you over temp the oil. Since that's not happening at autocross, there's no gain for using the thicker oil.

I think your logic for the 5W-40 makes sense. 5W is going to be close to (exactly?) the factory recommended cold weight, while the 40 should afford a little extra protection on hot days when running hard, at a small expense of fuel mileage and horsepower. I just wouldn't bother with using non-factory recommended oil weights unless you are in fact running the car hard in the hot. 5W-40 probably won't make a huge difference, but running 15W-50 or something in a street car that never really gets super hot oil temps is probably going to accelerate wear on the motor over the 0W-30/5W-30 factory spec oil.

Agreed.

[A1337STI]

I tend to use a thicker oil when my car eats it non stop. While will hurt the engine more in cold operation, but perhaps also help it out in cases where running 1-2 quarts low is harmful , the thicker stuff just doesn't get eaten as fast. (not sure if turbo seal or ring landing, could be a valve issue i guess too)

[Ms Heatha]

Originally Posted by A1337STI

I tend to use a thicker oil when my car eats it non stop. While will hurt the engine more in cold operation, but perhaps also help it out in cases where running 1-2 quarts low is harmful , the thicker stuff just doesn't get eaten as fast. (not sure if turbo seal or ring landing, could be a valve issue i guess too)

I had the same problem too...kind of. My old n/a engine wouldn't puke smoke until I hit the gas after letting it basically idle downhill for a minute. Boy, I could smoke up w whole intersection so bad that people could have thought it was a diesel in front of them. If that sounds like what yours is doing, here's your problem...bad valve guide seal.

[Kevin M]

Um, your engine didn't have a bad valve guide seal actually. From what I could tell, all the ring gaps on the #4 pistons had managed to align themselves. There was no scoring or damage to the cylinder or the piston when I tore it down, and replacing all of the valve guides hadn't solved the problem.

[sperry]

Originally Posted by Kevin M

Um, your engine didn't have a bad valve guide seal actually. From what I could tell, all the ring gaps on the #4 pistons had managed to align themselves. There was no scoring or damage to the cylinder or the piston when I tore it down, and replacing all of the valve guides hadn't solved the problem.

Clearly the problem is ghosts.

[Dean]

Originally Posted by sperry

Clearly the problem is ghost ninjas.

FIxed

[cody]

I still run the Rotella T6 and have even stopped switching to German Castrol for the Winter and just run the T6 year round. I feel like my car loves it and it's cheaper than GC. The T6 has slowly been crawling up in price at least at PepBoys which I buy it at since they have my favorite oil filter and using my Discover cashback to buy a $25 Pepboys gift card for $20 offsets it.

But the reason I'm bumping this thread is that I just found the 4qt jugs of Rotella T6 at the Walmart by The GSR for around $21.50/gallon jug. Not sure if this is something new or not, but there you go.

[100_Percent_Juice]

How much oil do you burn between changes?

[cody]

Originally Posted by 100_Percent_Juice

How much oil do you burn between changes?

I burn about 1 quart every 2K miles. The Royal Purple burned more quickly probably due to it's tendency to shear to a lighter weight toward the latter half of the OCI. I'm nearing the 150K mile mark. I could never tell a difference between the GC and the Rotella. I think I burned less of the GC, but that's probably because I ran it mainly in the Winter when I'm not racing.

[khail19]

Originally Posted by cody

But the reason I'm bumping this thread is that I just found the 4qt jugs of Rotella T6 at the Walmart by The GSR for around $21.50/gallon jug. Not sure if this is something new or not, but there you go.

Been this price for at least the last few months. I plan on switching to T6 as soon as my remaining stock is used up.