0W-40 in 1970 Cadillac Eldorado

Winter is going to be over before you reach a decision.

Reply to
jim
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Which is WHY I reccomend AGAINST mixing types and brands of oil.Use that solo can for something else.

I don't think motor oil has a great shelf life. I'd be leery of using it in a good engine. It breaks down. Ever see gasoline that has sat around in a tank for a long time?

Reply to
krp

Most synthetics are good oils. But is is not good to mix type of oils. Stick with whatever you have been using. Don't just switch back and forth because somebody tells you synthetics are good. Pick a lane and stay in it.

Reply to
krp

AutoZone has a brand called 'ValueCraft'. What manufacturing differences exist between something like that (the cheapest in their store) and, say, the major brand names? And in another forum I saw someone get really DOWN on the Pennsylvania oils (Quaker State, Pennzoil) as awful. What's the bias there?

Reply to
The Derfer

D> AutoZone has a brand called 'ValueCraft'. What manufacturing differences D> exist between something like that (the cheapest in their store) and, D> say, the major brand names?

Literal answer I don't know. If the package doesn't tell you, it could be almost anything. Could be old product Shell one can, old product Union oil in the next can. If it doesn't say on the package my bet is that the folks at the AZ store won't know any more than you would. I like to stick with what I KNOW is good.

D> And in another forum I saw someone get really DOWN on the Pennsylvania oils (Quaker State, Pennzoil) as awful. D> What's the bias there?

Sure and I share the bias against paraffin based oils. (Pennsylvania). If you have ever seen engines torn down you would too. They gunk the hell out of engines. Especially I would never use it in a modern high rev engines. They deposit sludge everywhere. Which is why I like the synthetics so well. With an older car like your eldo, where you have been using conventional oil, stick with it, but stick with the majors. Texaco, Union, Shell, Phillips etc. Just be consistent. Avoid the cheap oil unless your motor is shot.

Reply to
krp

Do you have an opinion on Mobil Clean 5000 and 7500?

Reply to
The Derfer

5000 is a conventional oil. Very good. 7500 is a synthetic, not as good as Mobil 1 but good. Both are older versions of newer oils. Look for the expiration dates on the case they came in.
Reply to
krp

Interesting. Mobil Clean 5000 comes in a 10W-40, I think that's what I'd prefer to go with in a 10W-40. I trust the brand well enough.

Last questions, slightly off-topic:

Does anyone recommend a "crank-case cleaner" to wash the gunk out of the engine? The type of fluid that you put into an empty crankcase, run the car for 10-15 minutes and then empty, and refill with oil afterward? I've heard those are mostly kerosene. I'm not sure if that's such a great idea since it may strip away deposits that maintain clearances within acceptable tolerance. At that point, I might have to go with 20W-50 all day every day, for example. Consider, though, that this is an OLD engine with low miles (actually closer to 57,000; I checked the other day). Would a regular diet of a double- does of Techron do just as well?

And what happened to SNAP brand lead substitute? It used to be the cheapest out there, now I have to buy 'Gunk' brand which is almost 2X more expensive. So few places carry a lead substitute on the shelves anymore. Frustrating. I always use 93 Octane.

I've tried Octane Boosters with varying success. This motor was used to 100-104 octane in its younger years. Is there an effective Octane booster that can get the engine a little more responsive these days? Someone suggested aviation fuel but with its explosive qualities, I wonder if plutonium would be just as wise.

Reply to
The Derfer

D> Interesting. Mobil Clean 5000 comes in a 10W-40, I D> think that's what I'd prefer to go with in a 10W-40. D> I trust the brand well enough.

I am not sure they are still making it. But it was known to be a very good oil.

D> Last questions, slightly off-topic:

D> Does anyone recommend a "crank-case cleaner" to D> wash the gunk out of the engine? The type of fluid that D> you put into an empty crankcase, run the car for 10-15 D> minutes and then empty, and refill with oil afterward?

Old mechanic's trick is to run automatic transmission fluid. I am not sure I really reccomend it. I have heard of engines giving up the ghost when cleaned like that. ATF is highly detergent. The process is to drain the oil and put on a CHEAP new filter. Fill with ATF. Drain replace with clean oil and a new filter. It may clean out TOO MUCH of the gunk. The engine may be depending on that gunk to function.

D> I've heard those are mostly kerosene. I'm not sure if that's D> such a great idea since it may strip away deposits D> that maintain clearances within acceptable tolerance.

ATF is highly detergent. It cleans everything. On an old engine it may have all kinds of problems. Better to either rebuild the engine or just use good oil and stick it out.

Reply to
krp

MobilClean is designed to be an extended change motor oil. Do you really plan to put enough miles on the engine for this to be an issue? On my '59 I change the oil in the spring and again in the fall and find that this is often less than 1500 miles on the oil.

Have you ever heard the saying "If it ain't broke, don't fix it"?

Steve B.

Reply to
Steve B.

I suppose a bottle of Techron every few months will be just as good.

Reply to
The Derfer

One of the problems with doing that to an OLD engine is that often they stop running and a rebuild becomes mandatory. The advice, "If it ain't broke don't fix it" is the best you'll ever get. Pouring lots of crap (chemicals) in an engine makes the companies that make the crap very happy, and can also serve to make all the companies that sell rebuild parts for engines VERY happy as well. One of my pet peeves is shadetree mechanic engine rebuilds. What you slap new rings and gaskets and hope like hell it runs when it is back together. If you are going to rebuild an engine, take it completely out of the vehicle. Strip it to the bare block. Send to to somebody reputable to be magnafluxed to check for any small cracks. Then "tank it" to clean all the gunk off its innards. They you have to check all of your tolerances for your crank journals and the cam. Most likely you'll need a new cam. New lifters etc... Redo the heads. Big job. Not all rebuilt "crate engines" are very good. Be sure of the source. I was in the parts business for a time. LOTS of bad crate motors especially on the big block engines. Like a 500 CID. Yes, a GOOD engine is going to cost you up the ass, but a cheap one costs even more.

Best to leave sleeping dogs lie. There are no miracles in a can. Just keep on with good oil and decent filters and stop playing games. Synthetic oil is good in a new engine. Even a new OLD engine. But screwing around with an old, old engine changing this is a high risk thing. It keeps coming back to; "If it ain't broke, don't fix it."

Reply to
krp

I don't think it would be a good idea to pour Techron into the crankcase.

--scott

Reply to
Scott Dorsey

Why won't this myth die after 30+ years of synthetic oils that are COMPLETELY compatible with all seal materials used since the 50s and all conventional oils????

As for the original question- you might join the forums on bobistheoilguy.com and bring it up there. I think the general consensus is that the Mobil "0wXX" oils have a very good base oil stock and are typically higher viscosity index (thin less as they get hotter) than the "5wXX" and "10wXX" versions (whether XX be 30 or 40). So I'd say give

0w40 a try if you want to. There is a subset on there who think Mobil is overpriced and will recommend Pennzoil Platinum or Castrol Edge... but any of the 3 are interchangeable in my book. I've had a longer history with Mobil 1 personally.

If it were me, I'd also seriously consider Shell RotellaT Synthetic

5w40. Its a diesel (really "heavy duty" is more accurate- it also meets all the gasoline ratings) engine oil and works very well in torquey, slow-turning engines like big-block v8s. And interestingly, the Subaru guys who autocross their WRX turbos also love it. I know for a fact that it doesn't thin out at high temperature as much as Mobil 1 5w30 does, having tried both in one of my old Mopar 440s. I've been using RotellaT for about 2 years now.
Reply to
Steve

Depends on which Rotella you're talking about. Regular Rotella T is conventional base stock. Rotella T Synthetic is Shell's XHVI (extreme high viscosity index) base stock. Its a "Group III+" base stock, refined from hydrocracker bottom slack wax and severely hydroprocessed, dewaxed, and further refined. Its wonderful stuff, and performs almost identically to Polyalphaolefin (Group IV) synthetics. In fact it carries additives a little BETTER than Group IV base stocks. Often PAO synthetics like Mobil 1 and others will add some conventional group II/III stock to the mix to carry additives that the PAO won't.

It appears that scare may have been greatly overblown. Certainly once a cam has been initially broken in, its need for high doses of ZDDP is about nil. Especially with factory valve springs that don't have a seat pressure of more than 300 lb or so. The latest diesel oils (Rotella- both flavors, Delvac and Delvac 1, Valvoline Premium Blue, Delo 400, etc.) are also reducing their zinc content, but at a slower rate than gasoline oils. The latest Rotellas are now gasoline SM and diesel CJ rated, which means that the zinc is coming way down.

Reply to
Steve

Why would you EVER run a 20w50 in anything that doesn't consume oil like a mosquito fogger?

Reply to
Steve

Because that is what the book recommends for the climate I live in? (several old VWs and a Porsche 944)

nate

Reply to
N8N

Completely? That's going overboard. Generally compatible. The POINT is that when you have been using regular oil there is NO benefit in switching to synthatic. The fault isn't in the synthetic oil, which is VASTLY superior to regular oil, but when you have 50,000 miles on an egine that has used conventional oils you already have the internal parts varnished. Synthetic do nothing for you. WHen you go from a buck something a quart to 6 bucks a quart it's stupid.

If you had followed this discussion several of us have suggested Shell Rotella and Texaco Havoline.

Reply to
krp

OK, air-coolers are a different story. But 20w50 in anything water-cooled in the US is just... odd. Maybe something that is so worn-out it can't hold oil pressure with anything else...

Reply to
Steve

No, just true. > The POINT

Yes, there is. Synthetic oils can let you extend your oil change interval even further than you can with conventional oil.

50,000 miles is a drop in the bucket, and if you have varnish or sludge at 50k you must either a) have a Toyota, or b) have found a stash of 1940s non-detergent oil. Good conventional oils don't "varnish" anything.

The difference between 1 buck for oil you'd damn well better change every 5000 miles, and 6 bucks per quart for oil that you change every

9000 miles is NEGLIGIBLE in comparison to the other costs of operating the vehicle. Especially for a rarely-driven car like this which needs the better acid buffering and moisture tolerance of a top grade oil.
Reply to
Steve

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