If anything, use 10w30 or (at most) 10w40. The 15w50 that Lingenfelter uses is meant for the specific tolerances that he uses in the engines he builds, which are different than that of our stock LS1 short block.....

We often forget to take into account who the engine was designed by. A stock motor that does not have the high performance internal modifications can not be treated asone that does have these modifications.

I have not yet heard a single bad thing about using 15w50... :confused:

I personal like the Mobil 1 0w30. It seems to have really no affect on my oil pressure and I know it's really good for hi temp in the day and cold at night. I know guys who race circle track and use 0w30 when they drive at night.

....Two things are at work here. The temperature issue impacts both the engine AND the oil. Getting an engine up to those kinds of temperatures can, over time, affect engine components themselves, independent of what the oil is doing. Just the temperature alone is more than most engines can handle on a regular basis.

Normal engine operating temperature for most engines is between 210 and 250 degrees. Granted, corvettes are designed to be driven fast and hard, to a certain extent, but pumping the temps up to such extremes will be rough on a Corvette engine too. Again, an engine can fail even if the oil is still "doing its thing", if components get too hot too frequently.

But, the temperature, as we both know, also affects the oil. The higher the temperature, the more quickly the oil will break down/sheer back/burn-off/etc. Viscosity retention is an issue that is affected in two ways by temperature increases. First, high temperature alone can cause temporary viscosity decreases in an oil if the viscosity index of the oil is not very high. Any temporary drop in viscosity has the potential for allowing metal to metal contact within an engine.

In addition, over time, high temperature and stress can cause the oil to have a permanent viscosity loss due to sheering. So, a 20w50 might shear back to more like a 20w40 or 20w30. The same could happen to other grades. The lower the viscosity, the lower the film strength (in a general sense) and the more chance for metal to metal contact.

An oil cooler is not a bad idea at all, as it will serve not only to prolong the life of the oil, but will also prolong the life of
engine components by keeping them cool, not to mention helping to maintain the film strength of the oil which prevents engine wear.

Secondarily, it might seem that it would also be a good idea to stick to as heavy a weight oil as you can, and hope it maintains that viscosity, but that's not necessarily right. There is a certain point at which, going heavier will only increase engine temperatures more by increasing INTERNAL friction within the oil itself. That is definitely NOT a benefit.

GM recommends 5w30 and 10w30 oils in basically ALL it's engines dating back to 92, including corvettes. Now, I know that many of these engines may be modified in certain ways, but oil galleries are likely to be the same or similar to the factory specs. As such, these galleries are designed for a specific weight of oil, or at least a specific range.

So, I wouldn't go over 10w40 in these Corvettes, no matter how much you feel like the 20w50 is going to "protect better". It's not a good idea. If you want more protection, look for a better oil, not a higher grade.

As an example, I know guys that have used just about any viscosity of any oil out there and were seeing failures. They
switched to AMSOIL Series 2000 0w30 and failures stopped and performance increased. These are guys racing in southern Texas, California, Arizona, etc. So, the weight of the oil is not necessarily the determining factor in how well the oil will protect. I've seen engine temperatures drop by 20 to 50 degrees F, using this oil. That is a HUGE drop. As much or more than an oil cooler might give.

Look for good specs in a weight close to what is recommended by the manufacturer. Pay special attention to HT/HS scores, NOACK, Flashpoint, VI and Four Ball, if available.

You want the HT/HS, Flash and VI to be as high as possible. NOACK and Four Ball as low as possible. Find an oil that fits that bill, and you've got an excellent oil. But, don't discount an oil just because one or two of those numbers aren't as "good" as you want. You want a whole package.

For instance, a good VI is important, but remember that this is not a spec that gives you a full picture. Some oils may start with a high VI, but this VI quickly decreases with use. Other oils start with a slightly lower VI, but maintain that VI for a very long time. That is because some oil manufacturers (petroleum and synthetic) PROP UP their VI numbers with viscosity modifiers. Other manufacturers use better quality basestocks so they don't have to. Those that are propped, quickly become UNpropped. That's a bad thing.

So, just be aware of what you're looking for in an oil and do whatever you can to keep engine temperatures as close to 250 as you can. You may not get there, but the lower you can go, the better off you'll be.

Best regards,
Michael Kaufman
Motor Oil Bible Author