My overly-paranoid procedure:

Good-quality 5w30 for the first 100 miles, change to good-quality 10w30 at 500 miles, change again at 1500 miles, then stick with 10w30 from then on at appropriate change intervals.

All changes with new filter, of course.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Yeah, that'd work

but honestly, I don't know any good arguments for running single-weight oil these days. Synthetics like Mobil-1 can achieve a 10w30 rating without any added friction modifiers. So you get all the benefit of a single-grade (no fricition modifiers), plus the cold flow rate of a multi-grade, plus the superior breakdown resistance of synthetic all in one package.

Aside from that it really doesn't matter how thin the oil gets when its hot, so long as the oil pump can maintain enough pressure to keep it going to all the right places, and so long as the oils film strength doesn't deteriorate. Film strength is not the same as viscosity.

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Exactly WHY do you want a few more pounds of oil pressure, assuming that your engine and oil pump are in good enough shape so that you have at least 10 at hot idle anyway?

You do realize, don't you, that when the indicated oil pressure goes UP due to the oil being thicker, the actual VOLUME FLOW RATE of oil through the system goes DOWN? If its 110 degrees outside and my engine is working hard, I'd much rather have 10 psi of pressure at idle / 45 psi at speed with thin oil flowing fast to cool the engine than have 20 psi at idle / 50 psi at speed because the thicker oil isn't circulating as fast and carrying the heat away as quickly.

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On the 440 I put together last Christmas, I broke it in for the first 20 minutes with Castrol GTX 10w30. Changed the oil and filter, ran the first 1000 miles on Castrol GTX 10w30. At that point I changed the oil and filter again switching to Mobil-1 Extended Life 10w30, which I intend to run for the life of the car.

That's exactly how I would break in any Mopar engine that didn't have race engine type (IOW, big) bearing clearances.

Breaking in on single-grade oil would be OK, but I really see no point and a few risks (such as poorer oil flow rate at the very time when localized heating due to the break-in process is at its greatest).

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Castrol - now there's some hype!

D/W

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If it ain't broke, fix it!

Castrol Syntec is all hype, almost as silly as Amsoil. Worse, really, because at least Amsoi *is* full synthetic (synthetic monkey whizz, maybe, but at least synthetic! )

The regular Castrol stuff has slightly better numbers than most comparable Valvoline products, though. All-around decent (not spectacular) oil for the money- which is why I use it for break-in only.

The other thing that surprised me is that the higher-end Pennzoil products are now showing really good performance in oil analyses. A far cry from 10 years ago!

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Come on folks listen to Dan he is right on the marker with this. Hell im not telling any one what brand of Mobil One 5w30 im racing in my car for the last four years. Thanks Possum










Hell Hath No Wrath Than A Possum Scorned

So, if I gather everything right, runnig Delo 40wt in socal, in a motor of questionable origin is not a bad choice.

Currently using Mobil I 5/30. Approaching 200K miles. Using an oil cooler which holds oil temps between 170 & 190. Oil psi ~ 35 @ 600 rpm idle & 50 highway. No appreciable oil use.

Mitch

OK, I’ll go along with you about 10W-30 being a good enough choice for a Slant 6. Slants are tough and are proven to live on abuse and they don’t make a lot of power. How else would so many have survived into this century after being run on who knows what for 40 years? What I won’t go along with however is that 10W-30 will protect an engine better than a straight 40wt or heavier viscosity muti-grade in extreme temperature/load situations. I also seriously doubt that a 40wt will damage an engine on startup when used in the non-winter months in an area where night time temperatures may only get down to 60-70 degrees F.

My feeling about the straight weight 40 oils comes from admittedly old experience racing motorcycles. In 1979 and 1980 American Honda supplied my endurance racing team with bikes to race. We asked them what oil they suggested and they told us to use a racing grade straight 40 weight. We used Kendall 40 Racing exclusively and had no engine failures in several thousand miles of racing. The engine internals looked great when Honda tore them down for school use when we were done with them. Maybe that’s no longer valid with today’s oil formulations but it worked for us.

On the topic of light weight oils, I believe that the trend has been driven by the US automakers trying desperately to attain slightly higher CAFE numbers that the light oils promote. I believe it’s about avoiding costly penalties and not about maximum engine life. See the statement below from NHTSA at:
http://www.nhtsa.dot.gov/cars/rules/cafe/overview.htm

"What is the penalty for not meeting CAFE requirements for any given model year (MY)?
The penalty for failing to meet CAFE standards recently increased from $5.00 to $5.50 per tenth of a mile per gallon for each tenth under the target value times the total volume of those vehicles manufactured for a given model year."


I work for a company that distributes vehicles for sale to the public with engines that rev as high as 16,000 rpm and make up to 213 hp/liter at the crank. For a Slant to reach that kind of efficiency it would be making 790 horsepower. What weight oil do we recommend for that machine which is used on public roads and has a one year warranty? We recommend 20W-40. For our lesser output models with engines that only pump 100 hp/liter we recommend 20W-40 for all temps over 40 degrees F. and 10W-30 for temperatures up to 60 degrees F. We have very few oil related engine failures.

We also sell off road racing models that use the same temperature/oil viscosity recommendations except that they call for a proprietary non-friction modified racing grade 15W-50 for use when the ambient air temperatures exceed 110 degrees F. Clearly our engineers believe that higher viscosity oils are called for when the temperature gets higher. Would Bob the oil guy say we are recommending the wrong oils?

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"Former Owner" of '65 Barracuda, 225, Auto, MP 2bbl intake, MP cam, Dutra Duals. Presently Moparless.

Oh, c'mon, now. Using 10w30 doesn't constitute "abuse" or settling for a choice that's only just "good enough".
Facts aren't on your side. *shrug*
Facts aren't on your side here, either, but carry on believing what you'd like to believe.
Running a slant-6 on the street in the here-and-now is about as far as it's possible to get from racing motorcycles in the way-back-when.
Certainly, but you'll notice nobody's suggesting the use of 5w20 engine oils in slant-6s, and those 5w20 oils are the ones that are being used nowtimes in North America (in engines that call for 5w30 or 10w30 elsewhere in the world) to squeeze out fractional improvements in CAFE ratings for the maker.
Sounds interesting...and different enough from the slant-6 that your oil recommendations for that engine do not speak to what works best in a slant-6.
I'm beginning to sound like a broken record, I'm sure, but so are you: Giving example after example of engine oil applications that are completely different from running a slant-6 on the street.
Donno, don't particularly care. I'm interested in what works best in a slant-6 on the street. There's no one single right answer for every slant-6 in every vehicle everywhere, but some of the extreme answers that've been posted in this thread (straight 50wt, for instance, or 20w50 on a brand new engine) are just plain unwise.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

But synthetic 10w30 is within 99&44/100% of being the single right answer for every slant-6 in every vehicle everywhere.





I'm DEAD serious. There's simply nothing about any single-weight oil that makes it superior to full synthetic 10w30, and a lot of things that make it inferior. There's NOTHING to recommend heavier grade oils over thinner oils of equivalent film strength. Multi-grade oils also tend to have better extreme pressure protection additives (ZDDP and similar) than single-grade oils.

Back in the days when thickness was the only way of propping up oils with primitive additive packages and poorer inherent film strength, it made sense. But the oils of today are way different from the oils of even as recent as 1990, let alone the 60s.

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I agree with you. And good-quality non-synthetic 10w30 comes in a close second. About the only instance I can think of where this wouldn't be the case would be a severely whipped, worn-out engine that will burn oil and have unacceptably low oil pressure unless a thicker grade is used. And maybe a (very) few extreme/severe race-only units deliberately built with very loose clearances.
Well, that's the problem, isn't it! Film strength cannot be seen as you pour the oil out of the bottle, while viscosity can, in a relative way. And, years ago there was a stronger link between viscosity and film strength. But, we're using today's oil now, not yesterday's oil back then. It can be very tough to make a leap of faith from a quantity you can see (viscosity) to one you can't (film strength) but that leap is quite necessary if the optimal grade of engine oil is to be selected.
Quite right.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Back in the 1950's and 60's, we ran straight 50 weight with a can of STP, in the flathead dirt track cars. Does anyone think that is the best solution for a street slant today?

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

I'm sure there are people who think that is the best solution for a street slant today...the same people who also think gasoline, coolant, tires, brakes, belts, hoses, and spark plugs were better in the 1950s than they are now.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.