(Probably not a good fit for our cars) The new Amsoil 5W-50!

[X25]

After reading a lot about oils, completing Bobistheoilguy.com's oil chapters, and talking to many others in other forums (mostly Mazda forums), I am convinced that this oil, as well as 15W-50, etc. are way too thick for our cars. I have just posted the following at another thread:

Originally Posted by X25

I've been discussing this with many at the Miata forums (for my supercharged Miata that overheats despite having an additional air-to-oil cooler with Mobil1 0W-40), and also ended up reading the whole oil university section of Bobstheoilguy.com. In short, my attitude is now changed a bit regarding oil pressures at the track.

Long story short, it is the flow that is most important, not the pressure. When we do a cold startup, we see very high oil pressures not because the oil is everywhere in the oil, lubricating the engine beautifully, but on the contrary, because the oil is too thick to go through the oil lines (especially the small ones in the engine), and it is creating a massive back pressure, creating those oil pressures we see and running most of the oil through the oil pump's bypass line, not through the engine.

There is currently no oil in the market which is thin enough for a cold start - NONE. Thinner oils will obviously come to enough flow faster, so the engine wear, most of which happens at the cold starts, will be less. Now, the question becomes, what should we do for the track duty?

The goal viscosity is actually 10 cSt. This is the target viscosity for 30 grade oil at operating temp, 212 degrees F. Now, when we get to 302 degrees F, 30 weight oil becomes around 3 cSt, while the 40 weight oil will hit around 3.7-3.8. You might say that it is 20+% more viscosity, but it is still just 1 cSt; they are actually almost identical! The significance of 1 cSt does not become 10x as important just because you have a very low value in hand. Granted, the best oil would stay at 10 viscosity across the board, but there is no such oil at the moment.

Assuming we use same base as GM recommends, i.e. 5W-XX oils, should we use 40 or 30 for track? 5W-30 will have marginally lower viscosity at 302 degrees F, but it will actually reduce the friction, reduce the likeliness of oil bypass valve (which opens up at 50 PSI?), and you will hit lower overall temps. It depends on the engine, but higher grade oil usually ends up increasing the PSI without necessarily increasing the actual flow of the oil.

Bob's recommendation in this regard is to observe the oil pressure at different RPM levels. If you hit 10 PSI at 1000 RPM, 20 at 2000, ... 50 PSI at 5000 RPM, then you're good. If you see higher, then you should consider trying a lower weight oil. I believe oil pressure relief valve opens up at 50 PSI, so there is no point in testing above 50 PSI; it will be misleading with the bypass circulation added to the equation. Actually, just so you know, if you hit 50 PSI at as low as 3000 RPM, then you will start circulating more and more oil above those RPMs, so you're doing pretty poorly. If you see very low PSI at idle at the track right when the engine is very hot, it is not the end of the world. After all, the oil is flowing without any resistance at high temps, and the engine does not need much protection at low RPMs anyway.

I intend to try 5W-30 next time at the track. If a ZL1 with its supercharger can survive 24 hours of torture at the track with this oil, so can my car at a simple track day. What's more, 5W-30 used oil reports have never raised any concern, and I will have reduced temps and better flow of oil when it's needed most as the advantage. I highly recommend reading Bob's oil university chapters.

[Norm Peterson]

The goal viscosity is actually 10 cSt. This is the target viscosity for 30 grade oil at operating temp, 212 degrees F. Now, when we get to 302 degrees F, 30 weight oil becomes around 3 cSt, while the 40 weight oil will hit around 3.7-3.8. You might say that it is 20+% more viscosity, but it is still just 1 cSt; they are actually almost identical! The significance of 1 cSt does not become 10x as important just because you have a very low value in hand. Granted, the best oil would stay at 10 viscosity across the board, but there is no such oil at the moment.

The only question in my mind involves the kind of relationship here. Is it linear (as I think you're suggesting), progressive (where the first 0.8 cSt added to 3.0 isn't worth as much as the 0.8cSt added to, say, 6.0), or digressive (the first added 0.8 buys you the biggest improvement that 0.8 cSt can give you)?

Has BITOG ever looked into that?


Norm

[White_SS/RS]

I've ran both 5/30 and 0/40 at the track and have analysis' done on 5/30 which have turned out great with none to minimal signs of wear metals. The minimal amounts are most likely due to a new engine (5K-ish miles at the time). The report also showed no signs of oil breakdown or stress from heat (290*+/-), so the 5/30 at least in my case is capable. (Side discussion but these results were one of the reasons I decided not to put an external oil cooler on the car.) Ayway, Like you said X25, the oil pressure at idle was pretty low, under 1 bar, so under 14.5 psi, and at higher engine speeds it was about 2.5 bar (36psi) if I recall.

Switching to 0/40 for me was a choice to solve a couple issues. Slightly bump oil pressure at idle and have a better additive package considering Im still using the Mobil 1 line of oil. Obviously the lower oil pressure from the 5/30 never caused issue but going to the 0/40 only slighly bumped it to about 1.3 bar (18psi), the higher RPM's would put the pressure to about 3.2 (46psi) which is about where the 5/30 was at during normal temp (220*)

I suppose going to an oil brand other than Mobil 1 I could find a better additive package in 5/30 but I'm still a little less enthused about oil pressure under 1 bar. Since the 0/40 puts pressure and flow back to whats normal with the 5/30, I think it would be acceptable to assume flow rate would also be back into the factory design perameters at elevated temps.

[L99CAMA2011]

Originally Posted by White_SS/RS

I've ran both 5/30 and 0/40 at the track and have analysis' done on 5/30 which have turned out great with none to minimal signs of wear metals. The minimal amounts are most likely due to a new engine (5K-ish miles at the time). The report also showed no signs of oil breakdown or stress from heat (290*+/-), so the 5/30 at least in my case is capable. (Side discussion but these results were one of the reasons I decided not to put an external oil cooler on the car.) Ayway, Like you said X25, the oil pressure at idle was pretty low, about 1 bar, so that's 14.5 psi, and at higher engine speeds it was about 2.6-2.8bar (38-40psi) if I recall.

Switching to 0/40 for me was a choice to solve a couple issues. Slightly bump oil pressure at idle and have a better additive package considering Im still using the Mobil 1 line of oil. Obviously the lower oil pressure from the 5/30 never caused issue but going to the 0/40 only slighly bumped it to about 1.5-1.8 bar (25psi), the higher RPM's would put the pressure to about 2.8-3.0 (40-43psi) which is about where the 5/30 was at during normal temp (220*)

I suppose going to an oil brand other than Mobil 1 I could find a better additive package in 5/30 but I'm still a little less enthused about oil pressure under 1 bar. Since the 0/40 puts pressure and flow back to whats normal with the 5/30, I think it would be acceptable to assume flow rate would also be back into the factory design perameters at elevated temps.

I like the Amsoil 0w-40 over the Mobil version.

[olblue75]

Ok I’m bringing this old thread back to life as I see Royal Purple has a 10W-60, they say it’s good for endurance or road racing, now get past the brand bashing, everyone has their choice good or bad let’s just stay with the weight not manufacturer.

I’m about to do a cam and complete head swap with springs etc etc and the guy that made all the suggestions backed out on me due to my lifter choice and he told me because of my cam profile and springs that Incant use a synthetic because it’s to slicks and the rollers might just slide vs roll over the cam. I just need to know what kinda oil additives wise I need phosphorus an what not.

[ariZona28]

I see nobody has given you any advice so I'm just going to throw out some basic opinions. I would stick with traditional, proven oil weights such as 5w-30 street, 15w-50 race (brand of your choice). This is the first I've heard of 10w-60. Seems like a solution to a problem that doesn't exist. I would definitely wait for other folks to be the test mules with that. Synthetic oil "too slick" for a roller cam? My experience with these new fangled contraptions is minimal but it sounds to me like you need to seek out a new builder. Maybe try to duplicate other people's successes with your build/oil choice. Try contacting the cam manufacturer for recommendations. No need to reinvent the wheel.

[olblue75]

I totally agree on a new builder he’s a bit on the arrogant side says he knows more than I’ll read on the internet and it’s all BS anyway. I’ll give comp cams a call since it’s one of their cams an RP an see what they say about it.

An it had a lot to do with with spring pressure and cam profile.