Quick oil question

Thustlewhumber · Feb 28, 2004

I have a slightly modified 351W in my 66 fastback with less than 5000 miles on it. I want to be able to switch to a synthetic oil when the time comes, but I want to know the right weight I should use. Mobil 1 synthetic was "accidentally" put in it for about 3-500 miles and I couldnt keep oil in it. I switched to a generic 30w and the oil consumption went away.

Anyway, I want to use Mobil 1 10w30 or Motorcraft 5w20, but I dont want to run through a quart of oil every 500 miles either (Mobil 1 is like water...). Anyone else with an older 351 have success with synthetic? If so, what weight do you use?

HistoricMustang · Feb 29, 2004

If your motor is using oil, it ain't the oils fault. Something else is going on. Mobil 1 is tops in my book and the weight depends somewhat on what part of the county to live in and how you use the car.

HistoricMustang
www.historicmustang.com

rbohm · Feb 29, 2004

historic is right, you have an oil leak somewhere, likely the rear main seal or the oil pan. repair it then run the 10w-30 mobil 1

68GEETEE · Feb 29, 2004

may be losing the oil in your valve guides or seals, or intake leak. even on a fresh rebuild, things sometimes go wrong.

65conv50 · Feb 29, 2004

Why would you want to use synthetic if your motor doesn't require it?? That's a lot of bucks down the drain every 3k!

Ozsum67 · Feb 29, 2004

If the synthetic was put in before the engine was broke in, oil consumption is normal. The rings have to be able to "cut" the crosshatch pattern of the cylinder walls in order to seat. Synthetic oil prevents this from happening because it is too slick. Once this happens, no amount of running will reverse it. There is a glaze that forms on the cylinder walls that has to be honed off. I've seen engines that actually had to be torn down again and re-hatched. For the poster that asked about the advantages of synthetic oil......you need to "read up". Older design engines need a longer break in period. And it does NOT mean babying the engine with low rpm running. Speeds need to be varied. Newer engines break in around 500 miles because of the design and closer tollerances.

65conv50 · Feb 29, 2004

Ozsum67 said:
the poster that asked about the advantages of synthetic oil......you need to "read up". Older design engines need a longer break in period. And it does NOT mean babying the engine with low rpm running. Speeds need to be varied. Newer engines break in around 500 miles because of the design and closer tollerances.

Older engines need about 1000 miles to break in. They should NEVER be run at low RPM or at a constant speed during this time. This is a myth that has been dead a long time. Normal driving, including some high speed, and careful not to hold constant RPM. Has nothing to do with oil.

Thustlewhumber · Feb 29, 2004

Here is what happened: There was a sliver of hard plastic that found its way into my oil pump. The oil pump couldnt compress it, so it locked up and shattered my distributor gear and part of the distributor. My dad works at a Cadillac dealership, and, after we put a new distributor and oil pump in, he just got some oil out of the 55 gallon drum and put in it. I didnt realize until after the fact that it was Mobil 1 (as required by all new Cadillacs).

I put generic "neon yellow" non-detergent oil in it for about 500 miles and I switched back to a 10w30 Mobil 1 Drive Clean. I noticed that Mobil1 tends to run a little thinner than normal oil, which is fine for newer engines, but I wondered if a little heavier oil would be better (or worse) for an older 351W.

It hasnt used a single drop of oil since I put Drive Clean in it, so I was just curious if I could go with 10w30 synthetic, or even that new 5w20 from Motorcraft. Of course, I guess I could just run both and see what happens

Ozsum67 · Mar 1, 2004

65conv50 said:
Older engines need about 1000 miles to break in. They should NEVER be run at low RPM or at a constant speed during this time. This is a myth that has been dead a long time. Normal driving, including some high speed, and careful not to hold constant RPM. Has nothing to do with oil.

I disagree. Older engines need 3000 miles to break in. We do agree on NO, LOW rpm break in. Perhaps you missed that.

RGS0907 · Mar 1, 2004

Thustlewhumber said:
It hasnt used a single drop of oil since I put Drive Clean in it, so I was just curious if I could go with 10w30 synthetic, or even that new 5w20 from Motorcraft. Of course, I guess I could just run both and see what happens

I would put in the same as the original specs. That's usually 10w30 for a street car...

65conv50 · Mar 1, 2004

Ozsum67 said:
I disagree. Older engines need 3000 miles to break in. We do agree on NO, LOW rpm break in. Perhaps you missed that.

Actually, both right. 1000 miles before really high speed driving - about 3k before it is really fully broken in. Of course this was for new engines. A rebuild today would depend on the tolerances and fit of the new parts and machine work. A competent shop would recommend based on their own experience.

Thustlewhumber · Mar 2, 2004

I have hyperutetic pistons and moly rings. Dont know if that helps any. I was told I could just drain all the water out of the radiator and let it overheat for a quick break in if I wanted...

If its not broken in yet, I'm sure it will be broken in when I get to Nashville in April.

Ozsum67 · Mar 2, 2004

Thustlewhumber said:
I have hyperutetic pistons and moly rings. Dont know if that helps any. I was told I could just drain all the water out of the radiator and let it overheat for a quick break in if I wanted...

If its not broken in yet, I'm sure it will be broken in when I get to Nashville in April.

I feel you are missing the concept of what "breaking in" actually is. You can't rush it. Only postpone it buy using synthetic oil too soon...which isn't a good thing. Break in speeds-rpms need to be varied, and that includes some high speed driving. Just not sustained high speed driving. When all is done, it is either broke in or it isn't. No kind-a sort-a broke in crap. Oil consumption will stop.

my66coupe · Mar 2, 2004

If you say you should'nt maintain RPMs for a long period of time, then why in talk, was there a thread about 2 grand for 20 minutes to break in a cam and fresh engine? Im sooo confused.

Mike

Ozsum67 · Mar 2, 2004

my66coupe said:
If you say you should'nt maintain RPMs for a long period of time, then why in talk, was there a thread about 2 grand for 20 minutes to break in a cam and fresh engine? Im sooo confused.

Mike

It is true that cams need to be broke in immediately, and I don't think 20 minutes is excessive. What I am saying is to not get on the highway at 70 mph, and set the thing on cruise,if you have one, and drive a few hundred miles.

Fredo · Mar 2, 2004

I have used Amsoil synthetic oils for years and I am very impressed with there products. They are the ones who invented synthetic oils 30 years ago.
Will AMSOIL Motor Oils decrease oil consumption?

Yes. When used in mechanically sound engines, AMSOIL Motor Oils can reduce oil consumption. Under test conditions, a reduction of as much as 42% was demonstrated for prolonged periods. However, this should not be taken to mean that AMSOIL Motor Oils are “cure-alls” for engines that consume oil because of mechanical problems.

Synthetic oils are made to protect and perform better than petroleum oils at both high and low temperature extremes. That’s why every jet engine in the world is lubricated with synthetic oil. AMSOIL Motor Oils have extremely low pour points and flow readily at extremely low temperatures for easier winter starting and significantly reduced engine wear. At high temperatures, no conventional motor oil can compare to the overall protection AMSOIL Synthetic Motor Oils provide. That’s extremely important for today’s turbocharged and small, non-turbocharged engines!
Check out there site at www.amsoil.com

RGS0907 · Mar 2, 2004

Fredo said:
...Synthetic oils are made to protect and perform better than petroleum oils at both high and low temperature extremes. That’s why every jet engine in the world is lubricated with synthetic oil. AMSOIL Motor Oils have extremely low pour points and flow readily at extremely low temperatures for easier winter starting and significantly reduced engine wear. At high temperatures, no conventional motor oil can compare to the overall protection AMSOIL Synthetic Motor Oils provide. That’s extremely important for today’s turbocharged and small, non-turbocharged engines!
Check out there site at www.amsoil.com

So what weight Amsoil oil would you recommend?

Fredo · Mar 2, 2004

5W30 is what I use in all my vehicles, but if you have an all out race engine Amsoil also makes a 20W50 race oil.

Ozsum67 · Mar 2, 2004

Fredo said:
I have used Amsoil synthetic oils for years and I am very impressed with there products. They are the ones who invented synthetic oils 30 years ago.
Will AMSOIL Motor Oils decrease oil consumption?

Yes. When used in mechanically sound engines, AMSOIL Motor Oils can reduce oil consumption. Under test conditions, a reduction of as much as 42% was demonstrated for prolonged periods. However, this should not be taken to mean that AMSOIL Motor Oils are “cure-alls” for engines that consume oil because of mechanical problems.

Synthetic oils are made to protect and perform better than petroleum oils at both high and low temperature extremes. That’s why every jet engine in the world is lubricated with synthetic oil. AMSOIL Motor Oils have extremely low pour points and flow readily at extremely low temperatures for easier winter starting and significantly reduced engine wear. At high temperatures, no conventional motor oil can compare to the overall protection AMSOIL Synthetic Motor Oils provide. That’s extremely important for today’s turbocharged and small, non-turbocharged engines!
Check out there site at www.amsoil.com

I won't debate the superiority of synthetic oils. I agree with you. The problems lie in using them too soon.

65conv50 · Mar 2, 2004

Ozsum67 said:
I disagree. Older engines need 3000 miles to break in. We do agree on NO, LOW rpm break in. Perhaps you missed that.

Actually, Ford said 1000 mile breakin. That ia the actual breakin period for 50s era cars, so 60s would probably be the same. I just looked it up in a 1954 Ford owner's manual. (I'm putting the manual on eBay - it's from my second car.. my first one was a 52 Ford Sunliner convert).

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