FYI FORD - MustangSteve's Ford Mustang Forum
The Internet's Most Knowledgeable Classic Mustang Information
IF YOU HAVE A QUESTION ABOUT CLASSIC FORD MUSTANGS, YOU HAVE COME TO THE RIGHT PLACE!
MustangSteve has over 30 years of Mustang experience, having owned 30 of them and restored several others. With the help of other Mustangers, this site is dedicated to helping anyone wanting to restore or modify their Mustang.... THERE ARE NO DUMB QUESTIONS!!!!!
Visit MustangSteve's web site to view some of my work and find details for:
FYIFORD Contributors' PICTURES - Power Brake Retrofit Kits for 65-66 Stangs - Classic Mustang FAQ's by MustangSteve - How to wire in a Duraspark Ignition - Mustang Ride Height Pictures and Descriptions - Steel Bushings to fit Granada Spindles to Mustang Tie Rods - Visit my EBAY store MustangSteve Performance - How to Install Granada Disc Brakes MustangSteve's Disc Brake Swap Page - FYIFORD Acronyms for guide to all the acronyms used on this page - FYIFORD Important information and upcoming events

You are not logged in. Would you like to login or register?

3/17/2019 8:26 AM  #1


What is a good oil viscosity for a rebuilt 347 engine.

I am putting mobile one in the car, just looking for the best viscosity. 10w-30? I don't really know what the numbers mean.

 

3/17/2019 8:35 AM  #2


Re: What is a good oil viscosity for a rebuilt 347 engine.

Or is Royal Purple a better choice?

     Thread Starter
 

3/17/2019 8:38 AM  #3


Re: What is a good oil viscosity for a rebuilt 347 engine.

10W30 is good for antique Mustang engines and Mini's.   It designates the viscosity of the oil. Some say it is the weight.


70, ragtop 351W/416 stroker Edel Performer heads w pro flow 4, Comp roller 35-421-8. T5
 

3/17/2019 8:52 AM  #4


Re: What is a good oil viscosity for a rebuilt 347 engine.

Ah yes, I need to change the 1979 Mini's oil too. Time to get the Olde British Lady out into the sun.

     Thread Starter
 

3/17/2019 9:12 AM  #5


Re: What is a good oil viscosity for a rebuilt 347 engine.

I didn't see your post on Royal Purple. I don't know anything about it, but I use synthetic oil in everything except airplanes. I took a 93 T-Bird engine apart at 180K and it still had the scratch marks in the cylinders.


70, ragtop 351W/416 stroker Edel Performer heads w pro flow 4, Comp roller 35-421-8. T5
 

3/17/2019 9:38 AM  #6


Re: What is a good oil viscosity for a rebuilt 347 engine.

This question can be debated for hours,

yep I've been researching oil for over 15 years.  I've asked a number of aeronautical engineers who are specialized in lube (there's a name for it, can't think of it)   All agreed the best for autos is a base stock  of PAO.  

I've only found and use one company that publish INDEPENDENT tests.

AMSOIL  

see here for many comparison tests.

  https://www.amsoil.com/why/why-synthetic.aspx  

I used my new 2001 Acura CL-S as a test mule.  Changed out factory oil at 3k mile and put in Amsoil 0w30 Signature, and a Amsoil filter.  Amsoil  states oil/filter combo good for 25k miles or 1 year (filter limited to 1 year)

I changed oil/filter every 10k miles because I was old school and used to 3k oil changes. 

Sent oil to lab (relax just 1 oz)  

I didn't believe results.

The TBN (total base number)  was 6.7 (New is 13-14).  Compared to NEW Pensoil test results a TBN 7-8.
Amsoil's independent lab recommended leave oil in and change filter only. Retest oil after 5k more miles.
They recommended change oil at 3 TBN.

I didn't leave oil/filter in longer than 10-12k miles.

I ran my test/analysis for about 60k miles , Wear metals results were about the same so I was't getting much wear out.

In a oil analysis there are many base metals and substances tested for (ie anti freeze) but for this re-cap TBN is used. 

I / my kid sold car after 260k miles. Never added any oil between changes.    

I don't use oil analysis anymore, just change out at 10k miles.  

There is a lot of debate on the web about oil. For me lab analysis worked.  





 


   
 

 

3/17/2019 10:28 AM  #7


Re: What is a good oil viscosity for a rebuilt 347 engine.

I’ve always been under the impression that the number represent how the oil reacts to temperature. If it’s cold, it won’t act any thicker than XXX and if it’s warm, it won’t act any thinner than XXX. I’ve heard guys talk about going with a thicker oil if the engine was set up with more clearance in the bearings!!

I like 10w-30 for my car. The crank and rod clearances were within factory specs. And the engine builder recommended it.

I like the Don’s responses and I will almost agree with the debate.....I think it would be more like months than hours!!!


John  -- 67 Mustang Coupe 390 5 speed
 

3/17/2019 10:38 AM  #8


Re: What is a good oil viscosity for a rebuilt 347 engine.

Mochaman wrote:

I am putting mobile one in the car, just looking for the best viscosity. 10w-30? I don't really know what the numbers mean.

Oil weight numbers are its resistance to flow. Low numbers flow easier than higher numbers. Multi grades flow like the lower number, but protect like the higher number.

Ol Bob the oil guy has more info than you have time to read:

https://www.bobistheoilguy.com/motor-oil-102/


Bob. 69 Mach 1, 393W, SMOD Toploader, Armstrong  steering, factory AC.
 

3/17/2019 6:28 PM  #9


Re: What is a good oil viscosity for a rebuilt 347 engine.

Well..............."Old Sal the know-it-all "sez..........Most oil could come outta the same hole!
When I worked at poop boyz I usta 'giggle-under-my-breath' when fellas would come in and spout off about how Castroil/Pennzoil/Havoline/Valvoline/Mobil One/Royal Purple..(pick one) is the best' blah-blah-blah!
IF you change it every 5/7/10 thousand miles get whats on sale and save the money$$$.
The filter is whats important more so than the oil.
ALL the oils for sale in these places are API approved(or whatever that acronym is!) They ALL are 'top shelf' stuff!! Don't fall for the hype/and ad blitz.

Oil filters.....AC Delco is rated pretty high/so is Purolator!...........Fram is still rated crappy!
Buy whats on sale and get a good filter.
Ya live in Texas..........5W30...10W30...5W20...workz great!!!
6sally6


Get busy Liv'in or get busy Die'n....Host of the 2020 Bash at the Beach/The only Bash that got cancelled  )8
 

3/17/2019 9:22 PM  #10


Re: What is a good oil viscosity for a rebuilt 347 engine.

To add to Don's post I did all the same stuff he did with that Tbird I mentioned. The only thing I would say different in my opinion would be that the magic is in the synthetic not the brand. Whatever you do DO NOT PUT FULL SYNTHETIC OIL IN AN AIRCRAFT PISTON ENGINE! THAT IS NOT AN OPINION. The manufactures of aircraft oil have removed it, but just incase.
   As far as the weight of the oil to use, I would stick with what Ford says to use for your year and size of engine. Nothing has changed for that particular engine since it was factory built. Even when it was overhauled it was done to original factory spec when it comes to bearing clearance. If it was modified otherwise the modifier of the particular part should have directed what oil to use.


70, ragtop 351W/416 stroker Edel Performer heads w pro flow 4, Comp roller 35-421-8. T5
 

3/17/2019 9:36 PM  #11


Re: What is a good oil viscosity for a rebuilt 347 engine.

Well Sal, this is probably the first time anyone has ever said this to you, you’re wrong! All those oils you listed are not the same. Some are dinosaur based and some of them are synthetic (mostly PAO). The synthetics will resist breakdown much longer than the petroleum based oils. The additive packages will break down before the synthetic base stock. If you change the filter every 3000-5000 miles and add a quart of new oil, synthetics might never have to be changed. One of the Ford engineering vice presidents ran a test with his personal company car, a new Lincoln. They ran dino oil for 10,000 miles to break in the engine. Then they put in synthetic oil (Mobil 1 I believe). From that point they changed the filter every 3000 miles and topped off with new synthetic. The filters were disected and examined for products of wear. At 100,000 miles they pulled the engine and tore it down for inspection. All the internal parts were within new part specification. Like Don said, run a good synthetic, change the filter regularly, and the engine will likely outlast the car.

The chemical plant where I worked made PAO (polyalphaolefin) base stock for synthetic oil and sold it to several brand names. We also made synthetic brake fluid base stock.

Mobil 1 made a name for themselves by being the first mass market fully synthetic engine oil. There have been questions in recent years about whether the quality is the same as it used to be. The specialty brands like Amsoil and Royal Purple exist as premium brands at premium prices, so they have to keep their quality at the highest level. I have used Amsoil for many years and I have met some of the principals of Royal Purple in Houston. Both brands are very good. The only difference may be the purple dye in the Royal Purple products.

The very best oil filters for your car are the ones sold at the dealership parts counter having the same logo as the one in the grill of your car. Several of the aftermarket oil filters are good, but you never know if their overpressure/bypass valve is correct for your engine. Hating on the Fram filter is a popular sport, but actual scientific testing does not show that they are as bad as the internet keyboard warriors say. I know for a fact that the Fram lawyers take a very dim view of public badmouthing of their products. My last boss was  a Porsche guy. He took his Boxster in for service and the service manager called him to tell him they found a Fram filter on the Boxster engine so they were voiding his warantee. He told the service manager he would call him back and called Fram’s legal department. The Fram lawyer asked for the contact information of the service manager. About half an hour later the service manager called my boss back to tell him that he had made a mistake and everything was just fine and they were going to give him an oil change for free for his trouble. I liked that story so much I asked for the Fram legal contact info. Less than a year later I took my Maxima in for service and while I was still filling out paperwok with the service writer a technician popped his head in to say “that car has a Fram filter on it”. The service writer put on his best “this is going to be bad news” face and gave me the same B.S. story about “voiding warantee”, and lecturing me on proper car care. I gave him the hand stop sign and told him “hold that thought”. I whipped out my cell phone and called Fram’s lawyers. Took me about a minute to give him the particulars. He asked me if the service writer was available. I told him he was standing right in front of me. He asked to speak to him so I handed him the phone and I couldn’t resist saying “it’s Fram’s lawyers”. The service writer listened to the lawyer for about five minutes, occasionally giving the lawyer info like his name, the dealership’s name, the dealership’s number, and finally “it’s not a Nissan policy, it’s instructions from the dealership management”. The service writer then spouted off a list of names and phone numbers. After he handed my phone back, the service writer told me there was no problem using the Fram filter. I wouldn’t have believed it if I hadn’t seen it. Be careful getting between someone and their income. Walmart has been selling Fram oil filters forever and they probably sell more oil filters than everyone else combined. That would not have continued on for so long if the Fram filters were technically deficient.

 

3/17/2019 9:42 PM  #12


Re: What is a good oil viscosity for a rebuilt 347 engine.

Hornman.........send me a PM, I need that phone number......

 

3/17/2019 9:55 PM  #13


Re: What is a good oil viscosity for a rebuilt 347 engine.

I have heard all that crap about Fram and about Penzoil since I was 16....that's a long time.  I have run Penz with Fram or Wix filters for ever and never had a failure or heavy sludge or any other problem.  I just recently started using Motorcraft Synthetic Blend since I started going to the dealer for oil changes and that's what they put in our two DDs so I use it in the Heap also....usually with a Fram filter.
The only oil I absolutely will not run is Valvolene.  Why?  Well, two days before Jean and I got hitched (over 50 years ago) I thought that I didn't have time to change the Penzoil in my 67 VW so I took it to a local shop.  He told me that he only used Valvolene so I gave in and let him go ahead.  Picked the car up and got on the freeway to drive about 10 miles to Long Beach.  Got off the freeway and pulled up to light....oil light came on.  NEVER had come on before.  After driving around and doing my biz I noticed that the oil light wasn't coming on at idle now.  Got on freeway, went back to Compton, got off the freeway....oil light came on at idle.  Went to shop and was told "Oh, you probably need a new oil pump."  Right!  Car had about 35K on it.  Drove home, stopped at Chief auto and grabbed three quarts of Penz 30, took the time to change the oil.  Oil light NEVER came on again and I sold the car at 94K.

BB

Last edited by Bullet Bob (3/17/2019 10:03 PM)


"you get what you pay for, good work isn't cheap, and there are NO free lunches...PERIOD!"
 

3/18/2019 8:16 AM  #14


Re: What is a good oil viscosity for a rebuilt 347 engine.

Make sure to break in the engine on conventional oil.  Synthetic is too slick and won't allow the rings to seat, and the engine will burn oil.  Factory engines that use synthetic use a different honing process for the bores than what a typical machine shop uses.  I would put at least 5,000 miles on the engine before switching it over to synthetic. 

5W30 was the weight specified for the 5.0 Mustangs, and likely that is what your stroker is based on.  I run 5W30 conventional in my '67's 289 with STP additive to ensure I have enough ZDDP for the flat tappet cam in the engine. 

Personally I'm not a fan of Mobil 1.  Everything I ever put it in developed leaks.  Possibly these were older engines and that was the cause, or possibly Mobil has changed their additive package over the years to combat this, but fool me once shame on you, fool me twice...

For synthetic I only run Amsoil.  I've never had it cause leaks, even when used in older engines.  I had to pull the heads off my WRX at about 200k and the complete lack of bore wear was astounding, as well as no sludge, or oil varnish on anything.  I've run Amsoil 5W30 in that car since 12k miles.

Oil continues to be a hotly debated topic.  Everyone has an opinion based on "experience".  This brand is great, this brand sucks, etc.  Truth be told its far, far more important that the oil and filter be changed at regular intervals rather than what the oil or filter are.  Engine longevity is more the product of maintenance that it is any particular product.  In a fun car, how many miles are you really going to put on it anyway?  If I'm lucky I log a couple thousand miles in my '67 a year.  At that rate it'll take me probably the rest of my life to put 50k on an engine. 

 

3/18/2019 1:31 PM  #15


Re: What is a good oil viscosity for a rebuilt 347 engine.

Cool story Ron!
My point (no matter how "lame") is.....Even using dino oil....IF you change it and the filter on a 3-5-7 thousand mile interval...its a safe bet the engine will last 100,000 +miles EZ.
Most of US....change the oil on a 6 month basis  more so than a mileage basis.
Also...when you "figger" OUR age.....how many miles a year we put on these "pampered-ponys".....well, the engine in my Mustang will prolly out live me! (That si of course...unless we DO have the invasion and whoever drops the EMP bomb and we need to revert back to non-computer cars AND IF we can get gasoline out of the storage tanks AND IF    theres a need to actually GO anywhere AND IF..... )
6s6


Get busy Liv'in or get busy Die'n....Host of the 2020 Bash at the Beach/The only Bash that got cancelled  )8
 

3/18/2019 5:41 PM  #16


Re: What is a good oil viscosity for a rebuilt 347 engine.

Yeah Sal, you are probably talking about 90% of the Forum members, but I was thinking about the few that autocross or road race (on real road race tracks), or even (shudder) drag race!!!! I have even heard about this newfangled car sport called drifting. Seems like the objective is to spin your tires all the way around the course. They even have special tires that give off colored smoke. Imagine that on the street: “I don’t know what kind of car it was officer, but it had green smoke coming off the tires. Darndest thing I ever seen”.

 

3/18/2019 10:29 PM  #17


Re: What is a good oil viscosity for a rebuilt 347 engine.

Can't say too much...I just dumped a bunch of 'cherry fragrance' fuel additive in my hot rod. . Sure beats the  smell of gas they sell now.
6sal6


Get busy Liv'in or get busy Die'n....Host of the 2020 Bash at the Beach/The only Bash that got cancelled  )8
 

3/19/2019 8:44 AM  #18


Re: What is a good oil viscosity for a rebuilt 347 engine.

Don wrote:

This question can be debated for hours,

yep I've been researching oil for over 15 years.  I've asked a number of aeronautical engineers who are specialized in lube (there's a name for it, can't think of it)   All agreed the best for autos is a base stock  of PAO.  

I've only found and use one company that publish INDEPENDENT tests.

AMSOIL  

see here for many comparison tests.

  https://www.amsoil.com/why/why-synthetic.aspx  

I used my new 2001 Acura CL-S as a test mule.  Changed out factory oil at 3k mile and put in Amsoil 0w30 Signature, and a Amsoil filter.  Amsoil  states oil/filter combo good for 25k miles or 1 year (filter limited to 1 year)

I changed oil/filter every 10k miles because I was old school and used to 3k oil changes. 

Sent oil to lab (relax just 1 oz)  

I didn't believe results.

The TBN (total base number)  was 6.7 (New is 13-14).  Compared to NEW Pensoil test results a TBN 7-8.
Amsoil's independent lab recommended leave oil in and change filter only. Retest oil after 5k more miles.
They recommended change oil at 3 TBN.

I didn't leave oil/filter in longer than 10-12k miles.

I ran my test/analysis for about 60k miles , Wear metals results were about the same so I was't getting much wear out.

In a oil analysis there are many base metals and substances tested for (ie anti freeze) but for this re-cap TBN is used. 

I / my kid sold car after 260k miles. Never added any oil between changes.    

I don't use oil analysis anymore, just change out at 10k miles.  

There is a lot of debate on the web about oil. For me lab analysis worked.  

The flaw in this test is that there was no control vehicle. You would need to follow the exact same procedures, change rates, driving style, etc with an identical Acura, using some of Sal’s Pep Boys straight 30wt lawnmower oil and compared the results at the end to have any sort of comparison.  Just because the Amsoil came out so well does not indicate another oil would not have similar results.

The oil requirements for an engine are based solely on the engine clearances and the temperatre at which the engine operates.





 


   
 

 


Money you enjoy wasting is NOT wasted money... unless your wife finds out.
 

3/19/2019 9:37 AM  #19


Re: What is a good oil viscosity for a rebuilt 347 engine.

MS wrote:

The flaw in this test is that there was no control vehicle. You would need to follow the exact same procedures, change rates, driving style, etc with an identical Acura, using some of Sal’s Pep Boys straight 30wt lawnmower oil and compared the results at the end to have any sort of comparison.  Just because the Amsoil came out so well does not indicate another oil would not have similar results.
 

Bingo!

 


Bob. 69 Mach 1, 393W, SMOD Toploader, Armstrong  steering, factory AC.
 

3/19/2019 10:46 AM  #20


Re: What is a good oil viscosity for a rebuilt 347 engine.

rpm wrote:

MS wrote:

The flaw in this test is that there was no control vehicle. You would need to follow the exact same procedures, change rates, driving style, etc with an identical Acura, using some of Sal’s Pep Boys straight 30wt lawnmower oil and compared the results at the end to have any sort of comparison. Just because the Amsoil came out so well does not indicate another oil would not have similar results.
 

Bingo!

 

as stated it was on my car NOT a control test.  The correct  test has been completed on fleets of taxis and trucks.  See Amsoil test page for data results.  Also SAE LAB stress tests have been completed using INDEPENDENT labs with  different makes of petro oil and oil listed as synthetic. All results were published and no manufacturer protested the results.     

My tests was to verify 10k oil changes because that was the cost break even point. FOR ME to not have to do 3k oil changes.

There are tests that verify less bearing wear. 

https://www.amsoil.com/newsstand/

   

 

 

Board footera


REMEMBER!!! When posting a question about your Mustang or other Ford on this forum, BE SURE to tell us what it is, what year, engine, etc so we have enough information to go on.