Best Engine Oil for Road Course Racing & Weekend Driving?

[Camaro Dude]

"Look at the relationship of kinematic viscosity @ 100C, divided by HT/HS viscosity @ 150C. The lower the number, the more shear stable the oil is.

TS"

Taken from here http://www.bobistheoilguy.com/forums...opics/125362/2

[X25]

Bob's take on the HTHS is that the difference between 3 and 3.7 is miniscule, and that it does not make much of a difference in practice. In other words, 1 cSt change in HTHS value does not make much of a difference, whether it's when the viscosity is at 60 when cold, or 3 when very hot. HTHS should not be your main concern per Bob.

[wakespeak]

Originally Posted by Camaro Dude

"Look at the relationship of kinematic viscosity @ 100C, divided by HT/HS viscosity @ 150C. The lower the number, the more shear stable the oil is.

TS"

Taken from here http://www.bobistheoilguy.com/forums...opics/125362/2

What they are saying in the thread is that some oils shear less over time than others, so change your oil more often is what i would say. It used to be pretty common for 5w30 to shear to a -20. HTHS is a short term measure at 150c or 302f with fresh oil. If you were to test it after 5000 miles some oils will have sheared down.

Bob is a great site but many of the comments have a (in my opinion) bias toward fuel economy and justifying long term drain intervals. So over time I have looked at engineering ratings to try to keep it objective. Oils are designed to meet an engineering spec. My favorite spec is ACEA A3 which is a high performance test without fuel economy as a primary. There are others like A5 that targets fuel economy more. Your call. You can also use the API ratings.

[X25]

Originally Posted by wakespeak

What they are saying in the thread is that some oils shear less over time than others, so change your oil more often is what i would say. It used to be pretty common for 5w30 to shear to a -20. HTHS is a short term measure at 150c or 302f with fresh oil. If you were to test it after 5000 miles some oils will have sheared down.

Bob is a great site but many of the comments have a (in my opinion) bias toward fuel economy and justifying long term drain intervals. So over time I have looked at engineering ratings to try to keep it objective. Oils are designed to meet an engineering spec. My favorite spec is ACEA A3 which is a high performance test without fuel economy as a primary. There are others like A5 that targets fuel economy more. Your call. You can also use the API ratings.

I highly recommend you read Bob's oil university. It will take an hour or two, but it's worth it! For instance, dino/blend oil goes down (in thickness) in the long run, but the synthetic oil actually goes up. In other words, the way dino and synthetic oils get to the oil specs is very different.

[wakespeak]

Originally Posted by X25

I highly recommend you read Bob's oil university. It will take an hour or two, but it's worth it! For instance, dino/blend oil goes down (in thickness) in the long run, but the synthetic oil actually goes up. In other words, the way dino and synthetic oils get to the oil specs is very different.

Ah, actually been a member of BITOG for 15ish years. If you drill on the data in the oil reports section you will find that some synthetics, like Amsoil's, go up in viscosity with use. Others go down, like Mobil 1, particularly their 0w-40. I just use the site now for mainly for the oil reports, and not for any guiding opinions. You should have been there during the Group III vs Group IV wars.

So back to viscosity and HTHS. If viscosity is a non-issue, then GM wouldn't want you to use 5w-30 vs 5w-20 at Ford, vs 0w-40 or even 10w-60 for most of the Europeans and Chrysler. Ford wouldn't tell you to use 5w-50 for track use, and likewise GM 15w-50. There have been several failures of the new LT1 and LT4, all "oil related" from what I have read.

To separate out the opinions I stumbled upon HTHS when looking for a standard that might apply to combined street/track use. I then looked for a targeted use case that would give me some context for what an HTHS value meant. European driving was closest. In Europe, cars are driven much more often near maximum output for extended periods. Someone (ACEA) decided over there that an HTHS of 3.5 is the line in the sand between high performance use and "regular" driving. Its a rule of thumb, not an absolute, because engines are designed differently, with yet another set of assumptions. Many US oils do not go through the ACEA certification process, but they do list HTHS, so it let me cross reference.

I disagree that the difference in HTHS of 3.0 and 3.7 is meaningless. It might be for a commuter car. But to me that is like saying having a 121 degree fever (23% higher than 98.6) for a human wouldn't affect how long you'd survive heavy physical activity. At some point any oil will break down.

For some newer engine designs, an HTHS of 3.0 might be fine with your foot floored at 6000 rpm. The Chevy LS engine is not one of those based on *my interpretation* reviewing oil analysis reports, which I will thank BITOG for, the manufacturer's recommendations, ACEA referencing, and guys on this site.

[X25]

Originally Posted by wakespeak

Ah, actually been a member of BITOG for 15ish years. If you drill on the data in the oil reports section you will find that some synthetics, like Amsoil's, go up in viscosity with use. Others go down, like Mobil 1, particularly their 0w-40. I just use the site now for mainly for the oil reports, and not for any guiding opinions. You should have been there during the Group III vs Group IV wars.

So back to viscosity and HTHS. If viscosity is a non-issue, then GM wouldn't want you to use 5w-30 vs 5w-20 at Ford, vs 0w-40 or even 10w-60 for most of the Europeans and Chrysler. Ford wouldn't tell you to use 5w-50 for track use, and likewise GM 15w-50. There have been several failures of the new LT1 and LT4, all "oil related" from what I have read.

To separate out the opinions I stumbled upon HTHS when looking for a standard that might apply to combined street/track use. I then looked for a targeted use case that would give me some context for what an HTHS value meant. European driving was closest. In Europe, cars are driven much more often near maximum output for extended periods. Someone (ACEA) decided over there that an HTHS of 3.5 is the line in the sand between high performance use and "regular" driving. Its a rule of thumb, not an absolute, because engines are designed differently, with yet another set of assumptions. Many US oils do not go through the ACEA certification process, but they do list HTHS, so it let me cross reference.

I disagree that the difference in HTHS of 3.0 and 3.7 is meaningless. It might be for a commuter car. But to me that is like saying having a 121 degree fever (23% higher than 98.6) for a human wouldn't affect how long you'd survive heavy physical activity. At some point any oil will break down.

For some newer engine designs, an HTHS of 3.0 might be fine with your foot floored at 6000 rpm. The Chevy LS engine is not one of those based on *my interpretation* reviewing oil analysis reports, which I will thank BITOG for, the manufacturer's recommendations, ACEA referencing, and guys on this site.

The oil results from 5W-30 from several members have all been very positive, so it gives me more courage to stick with that oil. I also got a sample myself from the oil I used when I hot 297 degrees F during my best lap; I wonder how it will turn out.

I understand the value of HTHS, and it makes complete sense if you happen to drive your car only at the race track since the oil will definitely be warm enough for it to perform, but the penalty you pay in daily driving is huge. Repeating your words, LS engines are not designed for it.

I know you've been a member for a long time, but did you happen to read the Motor oil university Bob has prepared? I'd highly recommend it
http://www.bobistheoilguy.com/motor-oil-101/

[wakespeak]

I read Motor oil university initially several years ago and I consider it opinion. The author AE Haas, is a plastic surgeon in FL, not a chemical or mechanical engineer, that has the time/money to research this stuff and is comfortable with his own conclusions. He uses a different oil in his Ferrari(s) than what Ferrari recommends and defends it, based on his research and street use of the car.

However if you look at his tables on 30 grade oils, you see that at 302F (150C) the oil has a cSt of 3, the same as a straight 2 oil at 212F. I am agreeing that a 30 is a good grade for the LS3, even on the track, but I am also saying to get a 30 that performs better (higher HTHS) than others at 150C, a temp easily reached in those conditions. For a lower HTHS of 3.0 such as Mobil 1, I think you need invest in coolers that keep the temp < 275F, or to be certain, 212F or 100C.

[Norm Peterson]

Originally Posted by wakespeak

So back to viscosity and HTHS. If viscosity is a non-issue, then GM wouldn't want you to use 5w-30 vs 5w-20 at Ford . . .

Just to add a little here, an engineer who was pretty close to the development of Ford's modular engines was adamant about NOT using the 5W-20 stuff in any modular engine. You may know who I'm talking about (he eventually became a engineer for one of the NASCAR Cup teams).

If he thinks that you need at least 5W-30 for durability reasons (over EPA & MPG g-g tax matters that are completely irrelevant out on the track), viscosity isn't a non-issue.


Norm