I asked this question both at Spring Mountain and in a different forum. At Spring Mountain I received a non-answer. In the other forum I received a dick-ish answer. Please allow me to ask here because I truly am curious about the option and would be grateful for a reasoned, factual reply: Wouldn't a compromise solution to the 5W30 vs 15W50 discussion be to run 10W40? If 5W30 is too "light" for summer or demanding driving conditions, and 15W50 is too "heavy" for everyday use, wouldn't running 10W40 satisfy all conditions?

Thanks, friends.

 

Well, to begin with I think your premise is flawed. 5w30 is not "too light" for summer use. I wonder where you got that idea. It is the recommended oil for other than track use for all temps above -20F. Would 10w40 work fine in hot summer weather? Yeah, probably it wouldn't cause any problems, but it won't flow as well when the engine is cold. And you'd want to be sure to change it out when the weather cools off. The oil passages are sized for the way the lighter weight oil flows when cold, and you might find the top end doesn't get oil fast enough in cold weather with thicker stuff. But I've not seen any evidence that 5W30 is inadequate, and 10W40 will have a negative impact on mileage. Small, but it's there.

Edit: Driving in mid-90s, stop and go traffic, I haven't seen my oil temp exceed about 200 degrees. Typically it's around 195. That's well within the margin of safety. Yes, it's hotter in the head than in the pan, but it's still not in any danger of breaking down. Monitor your oil temps and see what the car reports. I doubt it's going to be a problem, even in Las Vegas. much less Virginia.

On the other end, I wouldn't count on a 10W40 protecting well enough in high temp racing conditions. It's going to get a lot thinner at high temps than the 50W multi-grade. As the owners manual says:

 

This thread? https://www.corvetteforum.com/forums...the-track.html

 

I believe it calls for, in the owners manual and under the hood, using 5W30 Mobile One.

 

If you're going to run a 40 weight oil, you're much better off with Mobil 1 0w40 actually, as that's the factory fill oil in a lot of German cars and has passed a lot of their strict requirements. It's a very good oil with a proven track record, I've seen a lot of oil analysis reports on this oil and it's the real deal. It's the only oil I will run in my wife's BMW.

 

Better make sure that whatever you decide to use is dexos certified to maintain your warranty.

 

Probably poorly stated on my part. Not too light for routine summer driving. I have read the manual and I do monitor the oil temp. I even went so far as to run 5W30 in a HPDE at Summit Point in a chilly March without issues. What I would like to avoid is changing to 15W50 for a track day and then switching back to 5W30 for back on the street. During the tech discussion at Spring Mountain, the instructor actually told us 15W50 would be acceptable for everyday use if you allowed the engine to warm up adequately before driving. I am just wondering if there is any acceptable single-oil compromise that would accommodate street driving *and* HPDE days, and why Mobil 1 10W40 couldn't be that compromise.

 

What the instructor told you was correct. The fact that GM recommends the 15w50 for track use should be a clue. You also need to be careful with reving the engine while cold and pushing the engine 'til the oil temperature comes up.

The other downside is you will lose gas mileage. Most of this move to lower weight oils is for fuel economy to the detriment of engine life. Ford went from 30 to 20 weight without changing anything in the engines. Recently they introduced the Focus ST (turbo/intercooled) with 5w20 and quickly went to 5w30 after engine failures.

 

Then, aside from the mileage consideration, is this not another plus for moving to 10w40 as a reliable compromise solution (street and HPDE use)?

 

Think I would go to the 0w40 instead since GM already uses it in Europe. Heavier weight oil come into play at high rpm. Do you regularly see 5,000+ rpm.

 

or 5w50?

 

I think the Mobil 1 is 5w50 in Canada. I would stick with something that is GM approved in you want to keep your warranty.

 

I think I will stick with the synthetic option 5W-30. I will monitor the oil temp during occasional track driving. If it gets too high, I know the 15W-50 is needed. That is the only reason 15W-50 is specified for track driving because of oil temps.

 

Those are rare cases though. The switch to 5w20 engine oil has not caused more engine failures in most engines at all. There are a heck of a lot of Fords and Hondas out there with hundreds of thousands of miles on them that have run 5w20 or 0w20. They both introduced 5w20 in 2001, so we've had 15 years of proof that this thinner oil is not killing engines at all.

I wouldn't recommend running 5w20 in a C7 at all, however I know for a fact that the thinner oils are not trading engine life for fuel economy in the cars that have been running them for the past 15 years. I get an oil analysis done after every oil change I do on my cars, and engine wear in my 2006 Honda Civic has been very low and I run Mobil 1 0w20 in it.

 

Why not run 20 wt? You will pick up a little hp. Why do you think GM recommends 15w50 for track applications? If you putt around in your Corvette like most do 20wt should be fine. If your car regularly see higher rpm? The old rule of thumb was 10wt per 1,000 rpm.

 

If you only use your car for light duty driving at low RPMs, no sustained heavy loading, the factory recommended oil should be fine.

I just put the 15-50 Mobil 1 in my car for the summer as my driving tends to include high RPMs/low gears canyon (uphill, downhill) road driving conditions. Such driving creates tremendous amounts of heat, sending oil temperatures very high. Due to the lack of sufficient oil cooling for the C7 I feel far safer with the heavier oil.

Just as someone pointed out, always, but particularly with heavier oils, be easy on the RPMs and the accelerator until the oil reaches full operating temperatures. I always ran 20-50 Red Line oils in my high performance street, as well as in my dedicated race cars, always observing the cold-oil cautions and never had any oil related engine issues despite some ultra hard driving under both street and full-on track racing conditions.

 

The heavier weight oils as well as the 15w-50 for street use has been discussed quite a number of times. Most have their opinions, as discussed here. The truth is that a modern 5w-30 dexos1 oil (meaning semi-syn or full syn) is more than good enough for all but the MOST extreme conditions. The fact is that GM requires dexos1 certified oil for warranty compliance (not debating whether other oils are as good or better). The owners manual then recommends dexos1 certified 5w-30 for street use (except in extreme cold), and Mobil 1 15w-50 for track use (short term, but not dexos1 certified). Mobil 1 15w-50 is NOT recommended for extended use, and this too is stated in the manual. Why? Likely numerous reasons, some of which none of us may know. Additive packages are very important for the 7k+ mile drain intervals the OLI will give. And as below, the M1 15w-50 is NOT the same as the M1 5w-30 when it comes to formulation.

OP, from purely a warranty standpoint, I'd go with the manual's recommendations. The folks who designed the engine and spec'd the lubrication for 100k miles aren't idiots and have data to support their decisions. No oil heavier than Xw-30 is dexos1 certified. And unless you're seeing excessively high oil temperatures constantly with STREET driving, I can't see why a VERY safe choice isn't simply a top synthetic dexos1 5w-30 (many brands qualify here). I don't see a 10w-40 as striking a middle ground as you're already going against the GM recommendations and requirements. At that point, might as well use M1 15w-50.

https://www.corvetteforum.com/forums...post1589559223

And see here for the phosphorous and zinc (especially) differences between the Mobil 1 5w-30 and 15w-50:

https://mobiloil.com/~/media/amer/us...ecs-guide.ashx

 

As some have pointed out, the one and only reason for heavier oil when racing is oil/engine temperature. When you are racing, your engine runs a lot hotter, and it has nothing to do with hot summer weather or high RPM. It’s simply the high horsepower output for extended periods of time. Since all oil thins out as it gets hotter, 50 weight oil at typical racing oil temps of 260-290 is about the same thickness inside the engine’s bearings as 30 weight oil at street temps of 220-250. As long as your oil temp is below 250, you should use 5W-30, even if there are brief spikes above 250. You should only go to heavier oil if your oil temp consistently exceeds 250, which in most cases, only happens under racing conditions. Even with very spirited street use in hot summer weather, excursions above 250 are normally brief, and you’ll do yourself more harm by having too heavy an oil 98% of the time, than good from the added protection for those brief excursions. Remember, the heavier oil for racing is not to give thicker oil inside the bearings when racing. It is because racing makes oil hotter, which thins it out, so if you didn’t start out thicker, the oil in the bearings would be too thin at extra high racing temp. But if you aren’t going to be at the extra high temps of racing, you don’t need or want to start out thicker, because then you will be too thick inside the bearings.

 

Interesting discussion. I've been pondering this as I await delivery of my first Corvette.

Logically, an 0W oil would be best since we all know that most engine wear occurs at start up and the 0W oil will flow better/faster at low temps.

Its also my understanding that any 0W50 or 0W40 weight oil is, in all respects a 50 weight or 40 weight oil at normal operating temps with modifiers added to improve the cold temp flow characteristics.

I ran Amsoil 0W30 in my highly modified factory supercharged Mustang Cobra for over 100,000 miles with 2 or 3 track events every year for 10 years. Changed at 3000 mile intervals, the oil analysis routinely showed exceptionally good engine wear over that entire period.
Currently living in the Northeast,my first thought was to change to the recommended 15W50 before my first track event in the spring and change back to 5W30 after my last track day in the fall.
I expect to relocate to Florida in the next two years and at that time I may just stay with the 15W50 year round.
I also considered 0W40 full syn as a good compromise but after reading here, I am reevaluating that.

Here's a stupid question.
Does it make any sense to drain the oil into proper resealable containers for reuse. One jerry can for track and one jerry can for street and just switch them out as needed up to the normal life of the oil? bit of a pain but at $11.50/Qt for amsoil or redline, probably worth it. Especially if it preserves the factory warranty.

I may run this by the folks at Blackstone Labs and see what they say.

 

I wouldn't have a problem reusing oil as long as I was very clean in the collection, spotless oil pan, clean the area around the drain plug before you drain.