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Oil weight

109K views 449 replies 82 participants last post by  MartinT  
#1 ·
Hey everyone,
Loving my BRZ and looking to make sure she keeps going while I do some aggressive driving.
Those of you that occasionally track your cars, what are you using for oil weight? Sticking with the 0w20 or going heavier?
 
#7 ·
I'm not a tracker, but wouldn't it make the most sense to have a "street oil" and a "track oil"? Drain the street oil and fill with track oil for track day, then drain / recycle the track oil after the track day and go back to street oil. It seems like there's too much compromise trying to get an oil to do both. In any case, the oil will be pretty well shot at the end of the track day, so why not just put in the optimal track oil to begin with?

This presenter was talking about "0W-50 for the track guys" which I thought was interesting.
 
#15 ·
I run 5w30 on the street, it keeps me sane while I look at my oil pressure gauge lol.

For the sake of clarity: I use 5w30 because I'm not going to drop my oil and change it for a track day, just to switch back to 5w20. I didn't notice any change in fuel economy switching to it.
 
#16 ·
STI japan also recommend a 0-40 and 5-40 they have (its a motul oil).
 
#18 ·
Agree on the temps and how the car is used. Thicker grades definitely wont hurt anything from a reliability standpoint. The higher visc does offer more protection at operating temp. At the same time it creates more drag the engine has to overcome which reduces efficiency. If that seems not to be the case that typically points to engines designed with rather "loose" tolerances. Based on what I am seeing here with my 1st subaru, "loose tolerances" may as well be there slogan. So it makes sense. Lol
 
#21 ·
Hmm. I don't understand the recommendation for 5w20 at the track. 0w30 makes more sense. You want better retention of viscosity specs at sustained high temperatures. My oil temp is typically 248 - 252 on the track (90 degrees ambient temp). This is quite a bit better than the sustained 270 degree temps on my Camaro 1le with all of its cooling devices.
 
#22 ·
I would not recommend 5w20 for legit track duty either. Short little autocross runs and basic\hard street driving it will hold up well all while retaining factory MPG. A 5w30 or better yet 10w30 is a better option for dedicated track duty. Any oil with a 0 cold rating is a bad choice every time unless you live in the arctic circle.
 
#24 ·
Not "bad" but not "as good".
0w oils are nothing more than to keep the EPA whiners happy. Their protection and durability is absolutely without any doubt inferior to an oil with a 5w or 10w rating. I literally manufacture, sell , and test the viscosity modifiers that are used to make those oils change their cold ratings. I can tell you the less of them in your oil, the better. For a prius or little civic that just puts along... Sure whatever, they offer versatility in all weather and good fuel economy. For a high revving application that sees high temps and gets driven "spiritedly" you are doing your vehicle a disservice. Owners manuals are not bibles, and most people think engineers know more than they do, or that they actually try every oil weight under the sun. They dont. Subaru uses 2 weights of oil. Therefore everything they build will get 1 of the 2. Not because its the best, or even good, but because its what they have and what the EPA likes.
 
#35 ·
The 0 viscosity rated oils are not so much about emissions, per se, but about getting a good CAFE rating for the manufacturer. That tiny bit of extra MPG that you get with 0w oils may not seem like much, but when taken as an average of a manufacturer's total vehicle fleet it keeps them from having to pay gas guzzler taxes, and helps avoid other legislative BS. That fact that it increases wear is unimportant to the maker, they do want to sell you another car after all, and the more in your lifetime the better for them.
 
#38 ·
toyota owners manual says higher weight oil is recommended for severe duty or high performance. When done, 0w20 should be used again.

Redline sells "straight weight" oil that tends to last longer in severe duty applications. 20WT Race Oil (5W20)
I ran 30 weight in my spec miata. Other than the extreme cost, I'd run it in my 86 if I get back into track days.
 
#39 · (Edited)
My understanding has always been you can go lower on the first number and higher on the second number safely. The first number is the viscosity at cold start. The second number is what viscosity oil it behaves like as far as film thickness at high temperature. I would think a 0w-30 or 0w-40 would be ideal if they make it.

The best way I've heard it described is 0W-20 flows like a 0 weight oil but has the same protection as a 20 weight oil.
 
#54 ·
My understanding has always been you can go lower on the first number and higher on the second number safely. The first number is the viscosity at cold start. The second number is what viscosity oil it behaves like as far as film thickness at high temperature. I would think a 0w-30 or 0w-40 would be ideal if they make it.
from my understanding is you want to match the 2nd number(operating temp viscosity) to match your climate and usage. and the first number being closer to the 2nd number means less additives.

For What It's Worth, i just hit 1000 mi break-in, and my first oil change i put in 5W-20 Mobil 1 Synthetic. the factory oil it came with literally drained out like water, i'm guessing it was 0W-20.
 
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#40 ·
That is only somewhat true. In almost all cases you can safely go up in the 1st number as well. The exception being winter months in extremely cold climates. Dont pay attention to silly "scientific" oil tests you see on YouTube with guys tipping over tubes of oil and watching them race down a platform. Keep in mind the oil feed system is pressurized. It isnt just drizzling into the engine. It will get where it needs to be just fine in most cases even in the cold. I would highly recommend anyone avoid oils like the germans use. Things like 0w40 oil. In theory it sounds great. An oil that is super thin in the cold and has great high heat resistance from the added viscosity on the top end. In practice they just arent very good at protecting. It takes an immense amount of chemicals like viscocity modifiers and additives to make a fluid that can cover that wide of a spectrum. Problem with that is that you end up with more chemicals and less actual oil in your blend. Those chemicals break down much faster than the base oil itself. Oils made this way tend to lose lubricity and film strength very fast. No matter what oil change interval is recommended, you just cant run those oils that long, especially if the car will see any kind of severe use. Ideally what you want is to have the 2 numbers as close together as possible. For example a 5w20 will require less alteration to the base oil than a 0w20. A 10w30 will require less alteration than a 5w30 etc. I think 5w20 for street use with plenty of hard driving is fine all year round anywhere in the USA. For track I would use 10w30. No sense running anything too thick for street use. It does not protect any better if you are not getting it hot enough to matter.
 
#41 ·
I'm running autocross and track days with my car so I'm curious what the ideal number would be. In the past when I built LS engines the bearing clearance dictates what the first number of the oil weight will be. A heavier weight oil sounds great but if you're putting 25w50 ina engine that doesn't have big sloppy tolerances you're just making life harder for the oil pump and possibly losing flow to tiny oil gallies.