15w-50 Oil pro's and cons?

[AGP Turbo]

I've never even heard of an engine builder suggesting thinner oil for longevity. Only for slight HP gain. But making HP is super easy for us, so we are only looking for longevity.
20w-50 summer, 10w-40 winter.

[BiggFoot]

Dang I have been running 5W-30 HPS Royal Purple for 4 years but you guys have me scratching my head.

[AGP Turbo]

Originally Posted by BiggFoot

Dang I have been running 5W-30 HPS Royal Purple for 4 years but you guys have me scratching my head.

It's not a huge big deal at your power level. And you are running 30w. What we've seen really suck is even thinner oils than that. And 10yrs ago all the oils started to suck for EPA reasons, but those problems seem pretty well addressed by most manufacturers.

[JusticePete]

Originally Posted by UNRIVALED SS

Here we are again.

A few points to remember.

Pressure is inversely related to flow. Same with fuel.

The greater the difference in the hot and cold flow viscosity ratings the less resistance to shear. All other things equal.

More power creates more pressure/stress on engine parts which creates heat. Oil absorbed the heat and eventually is effected. So temps matter.

Bearing clearances matter. Go with the recommendations for whoever built it and watch the temps.

Most important change it more often when you push it hard and keep it clean.

Nicely written.

Originally Posted by Quicksilverman

Why would you want to use that thick of weight of motor oil? That thick of weight of motor oil is harder to flow through your engine to vital engine parts which will cause more wear over time. GM highly recommends only using 5W30 motor oil that is Dexos approved. We will only use 5W30 Valvoline Synpower motor oil in our Camaro.

RPM, pressure and temperature functionally reduce oil function, strength, sheer.

a 5 / 30 oil is supposed to protect like a 30 weight, but flow like a 5 weight. it is all good until the load between the bearing and crank combines with heat and high RPM to reduce a 30 weight oil to 20 weight. If your car is running rich, there may be enough gas mixing with the oil to reduce the protection weight even more until the oil is hot enough to cook it off.

That is why some builders want you to use 50w.

In a stock engine, the design is for a thin flow cold oil. When using 15w instead of 50w the owner has to be aware that the oil flow is reduced when the oil is cold and treat the engine accordingly. We use 15/50 winter and 20/50 summer in our tow vehicle because of the sustained high heat and loads during towing. Running a road course we have the same concern about heat and load, but for different reasons -- high RPM operation. That is why GM is telling people that track their cars to run 15 - 50 and then drain it and go back to the OE spec oil for street driving.

[UNRIVALED SS]

I have beat the hearing out of an LS engine back before I understood the differences in engine oils.

When I am racing I run Amsoil Dominator 15W50

The rest of the time I run Mobile 1 15W50 because you never know when a race will pop up $$$.

[Unavowed]

I would think that bearing clearances and ring gap should dictate oil weight more than FI/NA.

[AGP Turbo]

No. Ring gap is set 100% based on the estimated thermal expansion of the ring in the application. And bearing clearances are all about the same for all LS engines no matter what oil.

[Pollock]

I was concerned about mobile 15w50 myself. Having been using dyno 20w50 on my boat and it is really thick and pours slow. Well 15w50 synthetic pours out thin in my opinion. The oil pressure in my camaro is a bit higher but not a lot.
I let the car water temp get up to 170 or so before driving then wait till the oil is close to the 200 mark on the factory gauge before I get my foot into it. Should be fine and the added zinc should help with protection.

At the end of the day run what makes you sleep better at night. If gm recommends 15w50 for the track then the engine can handle it.

[UNRIVALED SS]

Also keep in mind. Coolant temps can be deceptive at startup.

Oil temps are what's important. Get that oil up to about 180 and flowing before you start pushing it. Seen a few impatient drivers make some constly mistakes with cool engine oil. Might have happened anyway, but why risk it?