Well I'm trying to talk her dad into changing the oil in the Dart over to 10W-40 full synth, but he still thinks that full 50W oil is best for the engine since the oil pump is failing and oil pressure is low (my guess is that either the gear is failing because of too much stress, or there's so much buildup in the pump itself or the pickup screen that it can't draw up enough oil from the pan to build up pressure).

The engine only has 75K miles on it, but has sat for long periods of time and gone VERY long times between oil changes. He used to mix 20W and 50W together when changing the oil, but his wive's friend's husband told him that mixing oil weights like that isn't a good idea. Now none of them want to put any lower weight oil in the engine because of the small amount of oil that stays in the engine when it gets drained mixing with the oil that gets put into the engine. I would say THAT small of an amount mixing in with new oil is negligible, but that actually mixing new oils together is a good thing to avoid.

He's got a LOT of dyno oil saved from when he bought it in bulk and he wants to at least use all that up before buying ny new oil, synthetic or otherwise.

I've got a pretty strong indication that there's a lot of gunk built up in the engine from all its time sitting between oil changes, so I'm trying to convince him to change (or have me change) the oil as soon as it gets dark, so as to keep it fresh before it has a chance to leave its own deposits and hopefully draw out some of the gunk that's built up.

I think changing with 10W-30 or 10W-40 dyno oil would be the best way to do this until it's all used up, or even straight 30W would be good enough to start with (I think he's got alot of that saved up).

To make a long story short, I'm confident that I can save the engine from a complete overhaul by changing to 10W-40 full synth as soon as possible and letting it absorb all the buildup over a few changes, and then by reworking the oil pump to keep it up to 35-40PSI on idle and 50-55PSI above 1600 RPM.

I'm hoping that getting some of your opinions might help me either find the best way to get the engine safely over to running full synth, or help me convince her folks that 10W-40 full synthetic is the way to go.

_________________
'74 Duster w/ HEI ignition, beat to snot suspension, A904, 8.25" 3.55 SG rear, still being tuned up and gets 17 MPG

Know how they always build a better idiot? That's me

why not just replace the pump? An once of prevention is worth a pound of cure.

That's part of the plan. Either replacing the pump or reworking the factory pump (and setting it to put out 35-40PSI at idle and 50-55PSI above 1600 RPM), then dropping the pan to pull and clean the oil pickup screen.

But that still leaves all the buildup in the oil passageways to worry about flushing out, which is one of several reasons I'm trying so hard to talk them into switching to synthetic as soon as possible.

_________________
'74 Duster w/ HEI ignition, beat to snot suspension, A904, 8.25" 3.55 SG rear, still being tuned up and gets 17 MPG

Know how they always build a better idiot? That's me

Why do you think synthetic will clean out all the sludge thats already there? To clean out sludge thats already there you should use some sort of engine flush. Because synthetic oil is runnier, it might get to various components better because of dirt in passageways, but I dont think it will do much to flush anything. Synthetic oil is inherently thinner and you will notice more leaks with an engine that has worn seals or gaskets. I'm pondering using synthetic in my engine but thats only becasue it was freshly built and hasn't even had the break in dino oil drained yet. Supposedly synthetic is too thin to use for break in hence why people say use dino to break engine in then go to synthetic.

With synthetic, it has a smaller molecular structure than dyno, so the next step up is what you need to equal a dino oil's weight (ie: 10W-40 dino = 15W-50 synth). Why they don't label the weights to compensate for this, I have no clue. I first used 10W-30 synthetic in my truck and it was like using 5W-20 dino, and my valves didn't like that one bit. But once I upped the weight, she's nice and smooth and gets about 1.5 miles more to the gallon after the sludge had been washed away.

Synthetic doesn't necessarily "flush" sludge out, but it will absorb it without leaving any of its own deposits like dino oil does. I switched the straight-6 in my truck over to synth a couple years back, and the first three changes came out black, but now it comes out as clean as new; even after 6K mile oil changes. It's more of an "as you use it" cleaning than an actual flush, so I guess I should have worded my original post differently. What I love is that now that my engine's clean I only have to change my oil twice a year (15W-50 for summer and 10W-40 for winter). The oil's pricey, but I still save money in the long run, which makes me and my engine happy. After using it, I've become a big fan of Mobil 1 full synthetic and K&N oil filters (funny note: my truck uses the same oil filter as a /6).

Something else I've considered to actually FLUSH the engine (after reworking the pump and pickup screen) was running 4 quarts of dino 10W-30 and a quart of ATF for two or three changes and changing at 1000 miles or less, but what I want to avoid is knocking chunks of sludge loose and ending up with a clog that could cause serious damage to a bearing or something else (which is why I like synthetic, because it just absorbed the stuff).

_________________
'74 Duster w/ HEI ignition, beat to snot suspension, A904, 8.25" 3.55 SG rear, still being tuned up and gets 17 MPG

Know how they always build a better idiot? That's me

as part of mazda factory training i had to sit thru an afternoon discussion on motor oils. it seemed kinda boring at first, but i think i learned quite a bit. first off, straight 50w oil, free or otherwise is really too thick for most automotive applications. second, as pierre said, synth won't clean your motor for you. and yes it is thinner by design so you will see less oil pressure and even more leaks. the reason for this is what i believe they call a smaller hyrodynamic wedge (i think of it as smaller ball bearings) so the oil is able to flow between tighter clearances inside the motor (go with heavier synth stuff in your slant.) another feature of modern oils is they remain stable over a wider temperature range. i forget the specifics, but oils marked 5w-50 have a much wider range than say 10w-30. the synthetics also last much longer than mineral based oils. if you change your oil every 3kmi or so, don't bother with synthetic. you may be able to get safely away with 5-6 kmi with the synthetic, but it still costs twice as much so you're not really saving much cash here. i'm not sure, but i don't think synth has much more of a shelf life than mineral based stuff once put into service (time between changes) since a lot of steam makes it's way into the crankcase as part of natural blowby and won't really get "cooked off" if it's not driven much.
as for cleaning the interior of the motor, there's no real way other than disassembling the whole works and cleaning each individual part. you may be able to get away with running some sort of flush solvent thru it and then pull the pan, valve cover and oil pump and scrub what's left with some engine brushes and more solvent.
at any rate, good luck on this project. sorry if i got a bit winded there!

-james

Mobil1 is about $5/qt locally here, Amsoil online is almost $6/qt, and redline locally is $9/qt while online is $7.something/qt. I think I can tolerate $25 oil changes especially seeing as I will probably be draining it half as often but $9 is pushing it. If I could find Amsoil locally I would probably use that but otherwise I'll probably end up with Mobil1 synthetic.

When I was looking around the local Kragen they had Mobil1 Synthetic "New Car Formula" and some other formula I can't remember off the top of my head. Any ideas on the difference?

I'm a complete Mobil 1 fan. Use it in every vehicle I work on. As far as the "New Car Formula" and the other kind, your guess is as good as mine, since all I see here is the various SuperSyn weights. I think Amsoil and Redline are pretty overrated (and way overpriced), given that I've never had (or heard of anyone else having) a single issue with Mobil 1 lubricants.

_________________
'74 Duster w/ HEI ignition, beat to snot suspension, A904, 8.25" 3.55 SG rear, still being tuned up and gets 17 MPG

Know how they always build a better idiot? That's me

Just my two cents worth, I have an 89 Isuzu trooper with 220,000 miles on the original engine with no oil use between changes which are every 3,000 miles,about every six to seven weeks. I use Castrol snytec blend. Supposedly half snythetic and 1/2 regular. I plan on using this in my rebuilt slant.. I guess it just comes down to what you've had positive rusults with. Thats the thing about oil and hot rods everybodys got an opinion (or two)

_________________
go fast, turn left, don't screw up.
WWW.Mopardropheadcoupe.com

I'm running three qts 0W-30 Mobil 1 (not a typo) and 2 qts 10W-30 Valvoline in my Duster. I run 65 psi oil pressure, and it maintains about 25 psi hot at idle on a "loose" bottom end. Dozens of hard quarter mile passes and 150 to 200 mile round trips to the tracks in super hot/miserable Georgia summertimes and I have not experienced any problems in several years. No science here, just decided to experiment with thin oil for less hp loss. I also run 75W-90 Mobil 1 in the rear end.

"DW"

_________________

If it ain't broke, fix it!

Yow, I would think that'd be way too thin (but I haven't experimented that thin either). What do you mean when you say a "loose" bottom end?

_________________
'74 Duster w/ HEI ignition, beat to snot suspension, A904, 8.25" 3.55 SG rear, still being tuned up and gets 17 MPG

Know how they always build a better idiot? That's me

clearances = loose end of specs.

It may be "way too thin", and I don't recommend it for others to try, necessarily, but it has worked for me so far. I threw it in for informational purposes. It's easier to wade through water than it is to wade through molasses, so it's easier for my crank to spin up in thinner oil, that's the physics. No, I don't run oil this thin in my daily drivers, either.

"DW"

_________________

If it ain't broke, fix it!

By the way, for the Dart that was the subject of the original post, might I suggest simply installing a high volume pump to make up for the worn out bottom end it sounds like it has, and run whatever oil floats your boat? Dial in about 50-60 psi pressure @ RPM, the high volume rotors will help it keep up the pressure at idle. Problem solved.

"DW"

_________________

If it ain't broke, fix it!

One of the local ma & pa auto stores got bought out by Monument, and they now carry all the Redline products. I thought the oil was mighty cheap! I just noticed even Summit has it listed for $8/qt. So if you have any Monument's around, it might be worth checking out.

hello sl6 sages/oil division specialists- what an interesting set of preceding views on oils for the slant. i must admit i learned a great deal by reading each one which surprised me since i already thought i knew much about earls for the sl6. first off what is dino oil exactly- never heard of it- some kind of break in oil back intheday? ive been fooling with slants since 64(for our young punkers- thats when LBJ was president and folks knew what the gulf of tonkin wasand gas was 24cents in asbury park )my viewfactoring in engine life. gas mileage, time spent and costs for a regular driver(12000 miles per year in nj which is probably the most difficult place to own a car- maybe nyc would be worse), a good 10-30 oil with oil and filter changes every 3-4000 miles seems best. how do i know- i followed this with all my slants since 64. in 93 i replacedmy 77 aspens sl6 with a rebuilt pep boys sl6 long block which now has another 100k on it with no problems. the first one went 260k and was burning oil due to shot valve guides. when i took off the pan, valve cover and oil pump cover that old engine was clean, no sludge anywhere even in the pan.the rebuilt is still run hard, and uses no oil between changes in 100k miles. i have heard no negatives from synthetic users, but none of them have verified the oft touted claim of higher gas mileage. i dont think its use and cost is justified except in special circumstances.is this story unusual- i invite your comments. incidentally i always have boughtpepboys or sears 10-30 which is much cheaper, has the same sae rating as name brands and i am told is made by the majors anyway(valvoline, pennzoil, etc.) . again what the hell is dino oil. regards callpaladin