That is OLD spec's. The original 2019 LT1 owners manual says specifically,,,,,, "Viscosity Grade, Use SAE 0W-40 viscosity grade engine oil". Specifically 0W-40 dexos2. Even this has been updated by GM, to the latest 0W-40 DexosR, specifically designed for high performance engines. All LT1 C7 engines are the same. Only if you can not get 0W-40 you can use the 5W-30 only as a backup. GM does not update their old car manuals.

 

OK, so the 5-30 is fine to use according to GM themselves. End of this movie then.

 

Yeah, so this video easily shows anyone that oil spread is NOT BS. And it shows that it's not ONLY an issue above 8000 miles.
This and other videos show viscosity index degradation is a problem after a few hundred miles. The 0W40 is more likely to sheer and drop a viscosity grade than a 5W30. That means the 0W40 is no longer a 40 weight because the viscosity additives are sheered over time. "More sheer equals more wear." Yes, the video you provide is great, but his point is a thicker oil is good for the bearing problem. Piggy-backing on that, 5W-30 is more likely to remain in it's viscosity index than a 0W40. This means that it would be thicker and better for you engine bearings.
Watch multiple videos from the Motor Oil Geek and also reread posts from LDB on this forum. Oil spread is not BS.

In reality, a person who barely drives their car or drives normally probably won't see a difference with the oil (0W40 or 5w30), but I don't like changing variables. Knowing that a 5W-30 will more than likely REMAIN a 30 weight than a 0W-40 will remain a 40 weight, I will choose consistency. Also, it was proven that GM will call for 5W-30 in other countries, but call for 0W-40 in this country FOR THE EXACT SAME ENGINE just because of CAFE standards.

 

Number 1. "Follow OEM recommendations" 0W-40. When you talk about the different oil spec's, it sounds like you are referring to the 0 in 0W, as a weight.

 

"START with the OEM recommendation". Again, he said that for people who don't know what to do, like the OP. The 0 or the 5 doesn't really matter in this topic except to give a starting point. The number that I'm talking about is the 30 or the 40. Viscosity is the correct term, not weight, but I'm assuming I'm talking to people that can go with the flow. Viscosity index improvers affect the last number, ie. 40 or 30. That 40 quickly shrinks to a 35, 30 then 25, so unless you plan on changing your oil every 1000 miles, you need to know that your viscosity grade is falling. Not a problem if you know that's happening and are okay with it. I'm okay knowing that but I'd feel more comfortable knowing my 30 will remain a 30 or really close to it since it's a more stable oil to begin with.

Again, use whatever oil you want. We all make personal choices, like oil brand. A lot of the time there is no rhyme or reason other than "that's what I think is best." I just stated what I use and backed it up with some facts that may or may not matter to anyone else. I will almost never parrot "Because that's what the manufacturer states" because they are wrong plenty. GM screwed up with oil. It started as 5w30, then went to 0w20 (not for our cars), then had to issue a correction to go to 0w40. They did it for CAFE standards, then had to fix it while still trying to meet CAFE standards, not what's really best for your car. Hence, 0w40.

Anyway, hope that clarifies anything.

 

30 and 40 is NOT viscosity. Viscosity changes at every degree of temperature. Weight doesn't change.

 

There is only one reason that I would switch over to 0W 40 Mobile 1 and that is because the engine is direct injection and that can let a little bit of gasoline pass into the cylinders and dilute the oil and make it thinner. So if I’m already using 0W 40 then it gives me some extra protection.

But over the past 20 years, Ford Chrysler and General Motors have all switched up their recommended oil for their engines. I’m just not eager to switch over to a 0w 40 oil when my Z51 is pumping 10 quarts of oil around. In addition, common sense tells me the thicker oil is going to put a slight drag when you rev the engine.

 

Ok, since you were proven wrong on your "spread is BS" comment you are trying to be super technical, way past the point of being constructive. I'm not trying to teach a class. I'm posting on a forum. If you want to completely miss the point to protect your ego, you do you

 

Geek guy was pretty adamant in his number one rule, to follow the manufacture recommendations. GM did change their original, "get better fuel economy spec", to, "lets try and save the engine spec". You have to give them credit. I do understand some people don't want to spend that much on their C7

 

OK, so then we are following their most recent recommendation by using 5w30 if we can't get or don't want to run 0w40. Cost has nothing to do with it for me.

 

And the problem is?

 

There have sure been a lot of threads on this topic since 0W40 appeared. Many posts argue that unless you are a seriously hard core track person (who will use 15W50 or even heavier), continued use of 5W30 is dumb even for drivers who are 100% street and whose oil thus essentially never gets above the lower middle 200’s. A few of those “5W30 is dumb” posts will acknowledge that if you run all the way to the oil life monitor limit before changing oil, using 0W40 introduces risk of VI improver breakdown. But they dismiss that by saying practically no Vette drivers run that long between oil changes. Color me dumb, because once out of warranty, being a 100% street driver with no short trip bad habits, I run 5W30 full synthetic using old fashioned personal limits of 12,000 miles or 18 months, ignoring the calendar time limits of current monitors. And I do so having spent a career in the oil industry with access to a ton of actual oil testing in real automobile engines run in long duration testing (which I unfortunately cannot share with you beyond my summarized posts is this and other forums).

A quick review of the VI improver problem is to remember the octopus analogy. VI improver molecules work by having long tentacles that wrap around their central body at lower temps, but unfurl and stick straight out as temp increases. When the arms stick straight out, they interfere with flow of base oil molecules, just like you would if you stuck your arms out while walking through a crowd of people. That flow interference counteracts the tendency of the base oil itself to thin out as temp increases. Trouble is, the VI improver arms can shear off, and when that happens, the effective upper number in the oil’s weight can degrade to about 25 higher than the W number, or 0W25 for the 0W40 oil.

There’s one more potential problem with VI improvers that I’ve never expressed on this forum before now. I’ll admit up front that the effect is almost certainly very small even if it exists, and I have no data to prove it exists at all. But since so many people cite such flimsy evidence to argue for wide spread oil with VI improvers, I figure I should be able to offer some flimsy thoughts to be against it. Remember the prior paragraph that VI improvers work by flow interference of a few molecules, not by magically improving the base oil molecules themselves. A wide spread oil might have 5% VI improver molecules. So 19 out of 20 molecules are the same old 25 spread molecules as they always were, while 1 out of 20 molecules is an octopus with arms sticking out and interfering with free flow and passage of the other 19 molecules. My intuition thinks that can’t be as effective as a lubricant as it would be if all 20 of the base oil molecules had been changed by a little bit. Or said another way, to achieve a certain viscosity, are 19 molecules of viscosity “A” plus 1 molecule of ultra high viscosity just as good a lubricant as 20 molecules of viscosity “A plus a little bit”? I have to believe that answer is no. Maybe the difference isn’t big, but I can’t believe it’s zero. And that, along with the much bigger and proven disadvantage of the VI improver shear problem, is why no oil with a spread greater than 25 will ever go into one of my cars until or unless somebody figures out how to make base oil with greater than 25 spread (or unless I started doing some track work, thus legitimately needing the wider spread, and was willing to change it much more often than my current personal guidelines stated earlier).

 

Thanks for the info LDB. Finally, we have someone who actually knows and can explain the science behind "viscosity improvers".

 

My question. Both the 5W-30 weight oil and the 0W-40 weight oil have HTHS, shearing at high pressure and temp. The 0W-40 has a wider spread and is more susceptible to sheer. But it starts at a higher weight. So doesn't it end up with a slightly higher weight/thickness than the 5W-30 even with the sheer.

 

No, because 0W40 is made from 0W25 base oil, and then you add enough VI improver to get it up to 0W40. Thus the 0W40 base oil is actually lighter than 5W30 base oil. Remember the octopus analogy. VI improver does not affect the W number because the octopus arms are all furled around the central body at low temp. The VI improver only adds to the upper number. Since the natural characteristics give full synthetic base oil of any weight about a 25 spread, 5W30 does not need much, if any VI improver. It’s just plain old base oil of the viscosity rating on the jug.

You of course will notice some weasel words like “about” and “not much, if any” in the prior paragraph because synthetic base oils do not all give precisely a 25 spread. So maybe some particular blend of 5W30 full synthetic needs a smidgen of VI improver, and maybe some particular blend of 0W40 starts with 0W23 or 0W27 base oil. But the basic story is correctly stated in the first paragraph.

 

This is my typical oil temperature after driving my 2016 Stingray Z51. I understand this is not a precise gauge but it looks like the temp is around 177-178 F. Maybe 0w-40 is not needed for my car.

I understand the push for 0w-40 Mobil 1 started after a very few 2014-2016 Stingrays (Z51 and non Z51) encountered engine failures on track days. I understand C7 engine oil temps can soar up to and beyond 280 F while on the track.

Rather than redesign the engine to improve the oil pan, oil pickup, baffling and pump calibration, GM came up with a new oil recommendation.

For me, it is not about the price of the oil. I will buy whatever oil is required. My concern is what will thicker oil do if it needs to flow into tiny places in the valve train but my engine oil temp never gets past 200 F.

Toyota recommends 0w-20 full synthetic for the V8 (with 32 valves) in my Tundra, and that is what I use. Tundras like mine are going beyond 300,000 miles. They have a towing capacity of 10,000 pounds.

 

Photomania, at that oil temp, unless you have an extended warranty that requires it, or change your driving habits so that you often run 200 and sometimes get to the mid-200’s, I see no reason for you to risk the 0W40 VI improver problem. For my driving habits, I would actually pay money to avoid a dry sump Vette because it extends warmup time, runs borderline too cold on oil on the street even when warmed up, and it isn’t even remotely needed on the high end. If I inherited a dry sump car, I might consider putting an oil temp thermostat its oil cooler to reduce the warmup time. Unless you are in a very cold climate and actually drive it in the winter (those in snow country seldom do), the 0W to 5W difference isn’t enough in my mind to justify the VI improver problem with 0W40.

As far as the Toyota Tundra comparison, I’d be reluctant to use that as justification to drop to 0W20 for your Vette situation. Bearing clearances, materials, and configuration also factor into oil viscosity recommendations. I have no idea how those factors compare between the two engines.

 

Thanks, LDB, for your helpful insight. When I bought the Stingray Z51, I didn’t know exactly what I was getting into. (Having to use four ramps to change oil, for example.)

I had spent six months looking for a blue Stingray with a manual transmission with low mileage and that’s when I found this one near me and it had only 13,000 miles on it and was in like new condition. So I bought it. The Z51 is not really what I would prefer now that I have one. But it is the coolest car I have ever owned.

 

Thanks LDB for bringing your knowledge. I haven't seen you post in a long time so I wasn't sure if you were still around. What you said is what I was trying to convey without attaching links to your old posts on this subject. Thanks!

 

I didn’t mean to be critical of Z51’s in any way. It’s a fine package that rates higher in the ultimate performance arena than the 3 standard Vettes I’ve owned. Trouble is, like other cars and situations, there are often tradeoffs. Better in one area can crate issues in others. But that doesn’t take away from coolness. And anyway, I’m certainly not one to talk. I recently took delivery on a Morgan (see avatar). It looks fantastic at least to my eye, performs on par with standard Vettes, and is an absolute blast to drive. But while the powertrain and chassis of these latest versions are modern, it has many carryovers from when they were first built in the 1930’s, including side curtains instead of side windows, and a top that takes several minutes and a nontrivial amount of colorful language to raise and lower. So enjoy your car’s coolness and regard any less than ideal features as “entertainment value”.