Quote:
Originally Posted by Shipkiller
Well, I use Redline 15W50. The engine runs cooler and for a side benefit I get 1-1.8 MPG better gas mileage on the highway.
I just got done pulling the oil pan to retrieve a valve shim. I also pulled an oil sample at the same time. This will be the first oil sample since I had my rod bearings changed 4000 miles ago... This starts the new baseline and time will tell.. I had nine track days on this oil.
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Quote:
Originally Posted by Shipkiller
You are partially correct.
A 5W50 viscosity motor oil would give you better flow in very cold temperatures over a 15W50 viscosity oil. What you have to do is look at the cold starting temperatures in your area. Are they in the teens? If so, a 5W would be better. If they seldom go below 30F, 15W would be ok.
A 5W has it's pour point specified down to -30C. A 15W pour point is specified down to -15C. I think a 15W would be ok down to zero.
Once your engine is at operating temperature, the oil is a 50 viscosity and so it will shear like a 50 (depending on it's manufacturer) so comparing a 5W50 to 15W50 for shear at operating temps is moot.
I always start my engine, put it in neutral and let it idle for a minute or maybe two. I put on my seat belt, adjust the seats, mirror etc.. This ensures the oil is flowing to ALL parts of the engine. I never just start the car and drive off.
I also never go above 4K RPM until the engine oil temperature gauge hits 180'. The colder the engine is, the easier I drive until it starts to generate some oil temperature.
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At what point is 15W50 better than 5W50 when it comes to adequate lubrication? From your second response above, best I can tell is the 5W50 may not be needed but why wouldn't you prefer it?
Also, why did you go with Redline 15W50 over the Redline 10W60? Seems like 10W60 would be the normal choice, any data to back up 15W50? You said lower operating temperature but wasn't this at the same time of changing weights and brands of oil? Just curious.
Some tiny amount better mpg makes no difference to me compared to a little less bearing wear.