FASTFATBOY

The cold start number is the first number listed "5"w30 or "15"w50, these are the numbers associated with cold start, although both numbers overlap each other to a certain extent.

The reason a thicker oil is considered for a track car is oil "shearing", when you run a car hard for that long at high oil temps the "grade" of oil is sheared down to a lower grade of protection, the theory is start higher-end higher.

But there is a point of diminishing returns.

insertclevername

Yes, you are correct concerning the cold weather reading on the bottle. However that is not consistent when the viscosity changes. Even with a 5w50, you still have a thicker oil at startup than a 5w30.

Here are the Mobil 1 examples, and these are at 104* f:

Mobil 1 5W-30
Viscosity, @ 40ºC, cSt (ASTM D445) 61.7
Viscosity @ 100ºC, cSt (ASTM D445) 11.0
Viscosity Index 172
Sulfated Ash, wt% (ASTM D874) 0.8
HTHS Viscosity, mPa•s @ 150ºC (ASTM D4683) 3.1
Pour Point, ºC (ASTM D97) -42
Flash Point, ºC (ASTM D92) 230
Density @15.6 ºC, kg/l (ASTM D4052) 0.855

Mobil 1 FS X2 5W-50
Viscosity, cSt ASTM D445
@ 40ºC 104.3
@ 100ºC 17.1
Viscosity Index 179
Sulfated Ash, wt% (ASTM D874) 1.34
Phosphorous, wt% (ASTM D4951) 0.1
Flash Point, ºC (ASTM D92) 232
Pour Point, ºC -42
Density @15ºC g/ml, (ASTM D4052) 0.8499
Total Base Number (ASTM D2896) 12.6
MRV at -35ºC, cP (ASTM D4684) 24800
HTHS Viscosity, mPa•s @ 150ºC (ASTM D4683) 4.4

That's a large difference, and it will be larger at 75*, closer to a startup for the better part of the year.

The best trade off is the 0w40, I could see this being left in the motor for track and street.

Mobil 1 FS 0W-40
Viscosity, cSt (ASTM D445)
@ 40ºC 71
@ 100ºC 12.9
Viscosity Index 186
MRV at -40ºC, cP (ASTM D4684) 21,600
HTHS Viscosity, mPa•s @ 150ºC (ASTM D4683) 3.6
Total Base Number (ASTM D2896) 12.6
Sulfated Ash, wt% (ASTM D874) 1.3
Phosphorous, wt% (ASTM D4981) 0.1
Flash Point, ºC (ASTM D92) 226
Density @ 15.6ºC, g/ml (ASTM D4052) 0.85

Even the 0w40 has more viscosity when cold, than the 5w30. This is the reason, that I think changing oil viscosity from track to street is best. A 0w30 for street, and a 0w40 for track (mild).

I myself would run a 5w30 synthetic on track, before I ran a 15w50 synthetic for daily street driving. Strictly based off startup and cold data.

FASTFATBOY

Depends on climate, I am in the southeast....not real cold here so I run the 0-40 all year round.

insertclevername

0w40 is the only grade I would leave in for daily as well as track. Besides 5w30 or daily 0w30.

That's a very good choice!

Apocolipse

I really hope where you live is not 75C in the summer...

insertclevername

This post only shows your inability to comprehend what you read. I converted c to f in my first remark of temperature, so the next number is a converted as well.

Really why?

Apocolipse

Makes sense to me, carry on.

bigmackloud

For comparison, here is the specs for the Rotella 5w40

V4kerker

jranaudo,
My real world results on a C6 base coupe between 5W-30 and 15W-50.
The oil temps were the same 280-300F, but the pressures were different at idle 18psig=5W-30 and 28psig=15W-50 after finishing a 20-30 minute session.

My DD on cold start-up with 15W-50 would take longer to load up the hydraulic lifters and get oil to all the lifters/rockers and oil pressure was higher +50psig.

jranaudo

Thanks folks. This was helpful!

QKSLVRZ

Didn't the oil guy rank the 0-40 M1 much lower than 5-30 M1?

Hat_Trick_Hokie

Another data point... put in Mobil 1 15w50 once it gets warm around May in the Mid Atlantic region and run that in my C5 LS1. Stock cooling all around. Put in Mobile 1 5w30 around October. No issues after 4 seasons.

Bill Dearborn

You have to consider fuel mileage in light of government regulations and how automakers try to eke out every little bit of fuel mileage to get a competitive rating. Going with a 15W50 means the oil is thicker and has more pumping losses which reduce mileage. It doesn't mean it causes increased engine wear. If that was a concern he would have mentioned it in a statement about how recommending 15W50 for the street would increase warranty issues just as he mentioned cat warranty issues if they recommended it. It was a nicely crafted statement that told people what they could do while still preaching the company line and avoiding other issues.

Bill

insertclevername

Interesting statement. Since we all agree the thicker oil has increased pumping losses. We know that oil flow(pumping) is lubrication, and lesser flow is poorer lubrication. Just because you are reading high oil psi at startup, doesn't mean you are pumping more and lubricating efficiently. The thicker oil is not flowing as well as a thinner oil, and psi is higher.(factory non high flow oil pump) Therefore at startup your motor is being deprived flow (lubrication) with the 15w50. While at startup the pumping losses are near 300% higher than a 5w30. We know a street driven vehicle will make numerous cold startups over time. Unless you will be getting the oil temps near 260*f for extended periods, the 15w50 is only going to have poorer flow due to the thickness. At normal operating temperatures, a 0w30 oil will provide all the flow, lubrication and sheer protection your motor will need.

Oil pumping (flow) = lubrication. There is no way around startup wear, but there is a way to minimize or maximize it. The viscosity chosen for daily will be a large factor.

I won't attempt to get in the head of Tadge, and guess why he said what he did, and didn't say what he didn't. He did recommend using different viscosity oil for daily and track. If you are reading between the lines, I would consider you ask the direct question of added wear at startup with 15w50 vs 5w30. The fuel mileage pickup, all though true, is small and the way you drive will have a larger impact on fuel mileage gains/losses. How large of an impact will the 15w50 oil contaminants have on the cats, I'm not sure how much quicker they will fail. Isn't the converter warranty like 8/80,000? These are as you said earlier, not big issues. I do know testing of engine wear, show close to 90% of it happens at startup. This is where thicker oils really have the poorer lubrication ability.

I would urge anyone to choose the oil viscosity wisely. Will you own the car long enough to need the motor rebuilt due to wear at startup due to running a thicker oil? I don't know, but why risk it?

I will continue to use 2 different viscosity oils for daily and track, or leave the 0w/5w30 in for track use. I consider it the best way to minimize the startup wear.

I'm no expert on the subject. I read test data and information on motor lubrication, and make sensible decisions from that data.

dapopa9

What are the thoughts on the Mobil 0w-50?

https://mobiloil.com/en/motor-oils/mobil-1/mobil-1-racing-oil

Apocolipse

Anytime you have a wide spread typically means viscosity improvers which tend to allow the oil to shear down quicker/easier.

insertclevername

This is a very good point to add. The loss of oil VII, is the reason we need to change out the oil frequently from use. When VII shear off the oil thickens.

VGLNTE1

Here is some real world experience for you. I ran 0-40 Mobil and my air ducting was still in a trial phase because I changed it all. My oil and water temp was 300°. Katech tech said the bearings were prob smoked, or worn. The car was fast so I said f it and put in another couple laps. When I had to rebuild due to the headgaskets, the bearings still looked brand new. This is also after using this motor for 8 years!! It's a forged 416 with clevite bearings. I tried 0-50 Mobil because the zinc ppm is so high, but at 15$ a quart it was just to expensive when an oil change is 9-10 quarts

TrackAire

I am going to respectfully disagree with a lot of notions you've listed here. I listed some facts in post 20 that it really does matter what rpm range you're running at when picking oil weights. Oil weight does not necessarily mean less oil flow. Also, depending on what rpm you're running, a lighter weight oil may not have a statistical difference in measurable flow in a hot engine when compared to a "thicker" rated oil.

There is no "start up wear" in today's modern motors. As long as basic maintenance is kept up to manufacturers requirements, name me one modern fuel injected car you or anybody you know with less than 250k miles that has "worn out" due to piston rings to cylinder clearance, worn out bearings or needing a valve job....it just doesn't happen any more with the introduction of fuel injection. The carburetor and choke was the reason engines use to "wear out" at 80k miles due to cylinder wall lubrication getting wash out and fuel contamination in the oil causing it to break down and be compressible.

The B.S. line you see in oil ads of "start up wear" is just them trying to scare the public into why their oil is better than the other guys. Ambient temps do matters, but if you're living in anything over 40 degrees F, you can pretty much run 15W-50 and you're never going to wear out your motor due to cold start up. In ads that claim up to 90% less wear on startup, what are they comparing? It's all marketing mumbo jumbo...90% wear of a minuscule number to begin with won't make statistical difference in your actual engine wear. They are not lying, but they are not telling the complete story. If start up wear was a real world issue, no mail delivery vehicle or UPS truck would ever make it past a couple of years of service.

Our engines are actually like hydraulic pumps using pressurized oil to keep metal to metal contact from happening. There is no metal to metal contact in your engine, everything is separated by a layer of oil at all times. If you've ever taken apart an engine that has been sitting for years, there is still oil on all the vertical parts. Oil flow in important but technically if you could pressurize the oil in the crank bearing to keep it separated (think "oil bearing") you wouldn't need flow other to dissipate the heat. Again, once the system is pressurized, you don't need flow other than to remove the heat on bearing surfaces. Notice engines only fail when they "lose pressure" or run out of oil, which essentially is he same as loss of pressure.

It doesn't matter if I drain 20W-50 or 15W-50 out of a hot engine, it pours out like water (exact opposite of what people think happens to hot oil). This thread is what oil is best for a track C5.....so we will not have to account sub freezing temps, stop and go driving, etc. The key to oil weight on a race car staying at high rpms for an extended period of time is how the oil reacts to the during those conditions. There is a reason both GM and SRT recommend a 15W-50 oil when on the track. It's not just flow, but aeration, shear strength, etc that has to be taken into account for.

insertclevername

I don't get the point of your post saying you disagree with me. I never said 15w50 was bad for anything more than cold startups. If you or anyone else wants to leave it in for daily, great, go ahead. I have already said using it for 260*f and up is good. Did you just feel like trying to school me? hahaha I just don't get it. I never mentioned rpm and viscosity. It does sound like you are saying you believe if you change oil viscosity while using the same oil pump, you will flow the same. If this is what you are saying, then I will disagree. Changing viscosity with the same oil pump will result in a change of psi. If you are reading higher, that would indicate, the pump is working harder to move oil through the motor. Lower psi would be the opposite. The key is finding the oil viscosity that has 10psi per 1000rpm. Some get all worried to see low oil pressure, but high oil pressure is just as bad. A high reading is showing a higher flow resistance, which could be internal issues or using to high viscosity oil.

The best thing for a motor oil is running it at operating temperature, minimal wear. Motor oils are lubricating at their peak at operating temperature. This is by design, not by accident. You have a lot of false hype statements, as well as some good ones in your post. This is my opinion.

If startup wear is just marketing hype, why are pre-lubers and block warmers being used? I agree since fuel injection came along, it minimized the startup wear. I recommend you open your mind that startup wear still occurs, no matter what viscosity oil you use. However the heavier you go, the longer it will take to pump it through the valleys, as well as it returning to the sump when at lower temps. The UPS etc vehicles are making numerous hot startups, the oil has thinned, this is eliminating the problem of flowing thick oil.

Well I don't remember GM recommending running 15w50 in the C5Z on track, just one quart higher. As far as I know the LS6 has some of the lowest on track oil issues. The newer engines are not doing as well, even with dry sumps. If GM is now coming out and saying run 15w50 on track, I see nothing wrong with that. I would do it, but I'm more concerned with lowering my oil temps on track. If I do that, I don't need to run a heavy oil on track. Unfortunately running heavier oils on track do not lower oil temps.

I don't understand why you chose to single me out. I didn't say anything controversial. I just suggested using two different viscosity oils for track and daily.

I really wasn't going to reply, given some of your statements. I don't have all the answers, I have added all I can, I feel I based my comments off testing and research of those that know way more than me. It also helps to use common sense with the results.