Originally Posted By: CATERHAM
But I will say this, I don't know of any engine that is still in by-pass running a 20 grade oil at normal operating temp's.
As I said, there are a few Chrysler engines that operate on the bypass frequently. I don't believe they are the only ones, we had a discussion on it recently.
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And while I am very familiar with some older engines with very low by-pass OP settings, they still are designed to be out of by-pass at normal operating temp's.
Yes, as I've posted about my experience with SBC's and SBF's in that regard. It doesn't mean that they are suffering damage while on the bypass though.
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Regarding MOPAR, I was recently talking to a member with a new Dodge Charger that has an OP gauge and the by-pass setting is at 139 psi! The OP test spec' at elivated rev's is 60 psi. Running the spec' 5W-20 not surprisingly he is rarely in by-pass mode.
That is similar to the pressure spec'd for the old Ford 351 Cleveland engine. Funny to see that again on something much newer.
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The point is, with most modern engines the recommended OP is well below the by-pass level, so if you still can't use maximum rev's without going into by-pass at maximum oil temp's, the oil is clearly way heavier than necessary to the point of being counterproductive.
It is ALWAYS well below the bypass; minimum safe OP has always been incredibly low, for an SBC it is something like 10psi, IIRC it was similar for the SBF. But even with the spec oil as hot as you could get it you'd never be anywhere near the minimum safe OP, you'd be 20+PSI above it. The only time you'd get OP that low was when there were no bearings left in the motor.
My old SBF would be on the relief with the 0w-40 in the pan at somewhere around 4,500RPM IIRC. It would still get onto the relief with 0w-20 in it somewhere around 5K, it was definitely lower than the limiter which was 6,250RPM. There was never any "problem" putting that engine onto the relief. When it was warm I beat on it like a red-headed step child and it outlasted two cars and still sits in my garage. That engine has been in pieces a couple of times and looks like the day it rolled off Ford's assembly line and has well over 200,000 miles on it, doesn't burn a drop of oil and still has 38psi hot at idle with a 0w-40 in the sump.
That said, it was
always warmed up before being hammered on. I think that's a more important point than ensuring you aren't on the relief at elevated revs when it is hot. There are many engines that are going to be on the relief at elevated revs by design. Any of the SBC and SBF builds I've been involved in or had the privilege of observing have been that way and those engines have lived long and healthy lives making a heck of a lot more power than they ever did new.
My M5 doesn't have an Oil Pressure gauge (BMW didn't apparently feel it was important, they want you to watch oil temperature instead), but I'm quite sure it is likely on the relief at higher rev's too, as a few guys have put gauges on them. Thinking of them with 10w-60 in the pan and how soon they are on the relief probably makes you uncomfortable, LOL