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Synthetic Oil

7K views 39 replies 20 participants last post by  JJHstang 
#1 ·
I was sure this was discussed but tried a search but only found for newer mustangs.
With the way current oil is without ZDDP,, should or shouldn't a person use synthetic oil?
I have 71 Mach 1 with a 351 W 4V . Don't know anything about the engine. Purchased it with the 351 W. It came from the factory with a 302 2V.
I have heard it can lubricate better including seals but may get leaks.
 
#5 ·
Do a search here on the forum, there are LOTS of current threads on this.

The short answer is that synthetic is just fine, just make sure you have higher levels of ZDDP for a flat tappet cam - if you have one.
 
#6 ·
I don't think there are any valid reasons for avoiding synthetic oils. Almost every refiner makes a high quality synthetic oil, so there are many fine choices.

The Mobil 1 15w-50 and 0w-40 are the two products I've been using since around 1999 and many tens of thousands of miles. No oiling issues, ever. Pick an oil with over 1000 ppm of zinc / phosphorus and you won't have any problems regardless of brand.

Z

PS. In the rare event you do get a oil leak after changing to a synthetic oil, just fix the leak, don't go back to conventional oils.
 
#10 ·
I don't think there are any valid reasons for avoiding synthetic oils. .
Cost is always valid when it conflicts ego with actual needs. $4 on 5qts might be 20-25%:x

After I did my research I also ended up with Mobile 1 15W-50. It has the same zinc and phosphorus level as the Valvoline VR1 oil.
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I hope you used valid info in your research, as in most current. The 15W-50 has gone down in ZDDP over the years from red cap to black cap now silver cap. Its still fine though.
VR1 is listed for racing/off-road for a reason. The consequence is it should be changed more frequently.:nerd:

ZDDP doesn't need to be the definitive factors anymore. Molybendum and Boron serve the same purposes.
 
#12 ·
This comes up a lot and if you can find them, there are threads with way more info than you want. Zray summed it up nicely. Mobil has taken the trouble to meet specifications with a couple of oils that many vintage Mercedes cars and Porsches require. And put it in writing. Unlike most other brands that hem and haw and rather vaguely "claim" to be good for various older cars. It so happens what is good for those older European cars is perfect for our old Ford engines. The specs are out there and previous discussions of this included a chart. Basically all you need to know is that some of the best synthetic motor oil ever for our cars is the 15W-50 and I just picked some up on sale at Wal Mart for $22 for 5 quarts. What may be the "best" is the Porsche spec 0-40 Zray also mentioned. It meets a higher standard, is not on sale like ever, and is really overkill for my 351W's if you ask me. Good stuff though. The weights are key. They don't sell a different version of 15W-50 that I've seen, if you see those numbers on the full synthetic bottle that's it. 10W-30 and 5W-20 are very different blends intended for different engines.

I have a Japanese engined vehicle that I decided to treat to Mobil 1 10W-30 (correct for 1990's Asian stuff) after a long life of (I imagine) the cheapest oil available. It was unhappy and immediately started leaking small rivers of oil. Mostly from the cam plugs, valve covers, and distributor seal. Never leaked a drop before. That one didn't go too well but new gaskets and seals I've bothered to put on seem to have corked it up. (I still haven't finished changing ALL the gaskets. I don't value the vehicle highly enough.) I've yet to see such issues swapping Fords (new and old) over to synthetic but I keep a sharp eye.

Dirty little secret. If a car smokes blue smoke visibly out of the tail pipe, you can change it over to full synthetic Mobil 1 and the blue smoke will almost disappear about the second oil change. It's still burning oil just as bad, but you and everyone can no longer really see it.
 
#14 ·
A coworker and I were just recently discussing this subject and doing a bit of google research on the matter. Like others have stated, besides cost differential (which is shrinking quite a bit these days) there is nothing but positives switching to a full synthetic. I just switched my Mustang over from the Delo 15w-40 diesel oil to the Mobil 15w-50 synthetic. I am approaching 80k miles on my 351w, and it’s still going strong.

Regarding the leaks after switching over... synthetic oils tend to clean the motor better than conventional oils. So all those years of running oil that deposits goo on everything, including your seals, the synthetic flushes the goo out which can then cause a leak if the goo was acting like a seal on an already compromised seal. I’m crossing my fingers mine doesn’t develop any leaks after the switch ?
 
#15 ·
For some reason a few people still insist on running diesel oil in gasoline engines. There was discussion at another board some time back where an actually qualified petroleum engineer chimed in wondering why in the world would people do such a thing. It implied to him that his entire career spent carefully designing additive packages to best suit the needs of particular engines was a complete waste of time. "Completely ignore what it says on the label and do the opposite. Just pour in any old crap some random guys on the internet say is better with absolutely no scientific evidence to support doing so." He was fairly annoyed about it. I found it very amusing.

It's been pointed out before here that diesel engine oil happens to have an additive in it which makes it suitable for use in many motorcycles that use motor oil in their transmissions and have a "wet clutch". This is a valid practice. The reason to do so is that motorcycle specific oil costs more and is less widely available. None of which is relevant at all to old Mustangs.
 
#16 · (Edited)
Ya, been through this before. Remember this? Maybe some tribologists are just smarter than others or some are Henny Pennys. Apparently a secret cohort of rebels have made an earl that satisfies the needs of three engine applications and meet the critical specs, or maybe its a fake label. So don't trust labels then.
:wave:

As for the 15w50 changing formulations, apparently the last change was for the better, compare the two separated by 5 years. The latest ones were all over 1300. There are always batch variations though.


(ooops, the last is the racing formula which is even higher today.)

If you could find historic data many oils of the 60's have similar levels of ZDDP to today's SM/SN oils and cars lasted fine for the most part and many of ours still would. The need for more pressure protection really becomes evident with higher spring pressures, solid lifters and more radical cams.

And for the OP since the he asked yes, synthetics might make a leak more apparent as it removes crude from around a seal. I have seen the "high mileage" formulas help stop it in such cases.
 
#17 ·
Ya, been through this before. Remember this? Maybe some tribologists are just smarter than others or some are Henny Pennys. Apparently a secret cohort of rebels have made an earl that satisfies the needs of three engine applications and meet the critical specs, or maybe its a fake label. So don't trust labels then.
Lost me. I see diesel specific API certifications that are more related to the sulfur content of the fuel used in diesels of particular year models clear and mentions of the oil being specific to diesel mention use on that label. So what I see is a label indication that T6 is a pretty darn good oil designed for diesel engines and no reason to distrust it. Am I missing something?
 
#20 ·
Many of them are loosing or removing their API certification status' for the same reason Joe Gibbs, Redline, Royal Purple and some Amsoils don't use them. It costs big bucks to be certified and/or they have levels of ZDDP that exceed what certifications allow.

Just post one link to a cited article or product advertisement that says not to use HDEO in a no-smog gasoline engine and I'll wager mine or any ones eternal silence it can be invalidated.
 
#23 ·
OK, OK, now I see that little "/SM" tagged on the very tail end of all those diesel API specs. Personally I find API specs not really relevant to vintage engines anymore. ACEA specs are more like where it's at for those, if you ask me. But I'm not making it my life's work to study engine oils. I do know my gasoline engines do not need additives to keep the diesel soot in suspension. For newer car that is changing somewhat. The newer GDI engines are having fuel particulate buildup issues very similar to what high sulfur diesel engines suffer. With GDI engines needing particulate suspension and diesels needing less help due to lower sulfur fuels it's likely the engine oils for some new gas and diesel engines will indeed converge. According to that T6 label, maybe they already are doing so. Again, none of which reasonably applies to our antique cars. Just casually of interest to folks who follow such things.
 
#24 ·
From What i read I wouldn't worry about ZDDP

once the damage is done its done. and if you dont beat on the car or use it for racing or towing the wear will be very minimal for a show car
 
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#26 ·
Hello,
The main oil related engine problem due to incorrect oil used in older engines is camshaft failure. The nature of the this failure is the camshaft lobes disappear because modern oils (including synthetic) are designed for low friction contact. e.g. Roller Camshaft/Lifters.
Put simply, newer oils don't offer protection needed for "Flat" Tappet camshafts.
A secondary consideration is incompatibility with older bearing materials.
....Installing a mild Roller Cam and lifters is one way of insuring reliability.
....Finding an oil that is the correct API rating is the other solution.
see Summit Racing https://www.onallcylinders.com/2019/03/26/video-api-oil-ratings-mean/ for a better understanding of this

Cheers Spanner
 
#28 ·
Many here have thousands of miles on quality synthetics. As long as the zddp content is high enough, which is the case with most modern synthetics,you’ll be fine. The exception is during break in when you’re most likely to wipe a cam. Using either a break in oil or an additive is just fine. I’ve been doing it for the last couple of decades mostly with race engines.
 
#27 ·
Daveoxide,
Let me know if you start to have leaks. That is my main concern. What year is your Mustang?
I have no idea of how many miles on my 351W.
My 71 came with a 302 2v out if the factory but somewhere along the way it got replaced with the 351W.
 
#31 ·
Have over the years used Pennzoil 10w-40 with bottle of ZDDP in I6 that was a "street" survivor, mileage unknown, that I have not touched to date since I purchased car in 2010. In my last oil change switched to Royal Purple HPS 10w-30. It has zinc and phosporus and is appropriate for flat tappet lifters. I used 10w-30, because it was what was originally recommended for this motor by Ford. No leaks. However now experiencing rich gas smell on cold starts and acceleration. I also have reports of white smoke. Pulled plugs; 1,2,3 are ok. Numbers 4 and 5 are oil fouled. Number 6 is ok. Really don't think that the synthetic oil is causing this problem. Really think I have a worn out 200. Open to any comments or suggestions.
 
#32 ·
One of the better oil threads imo. I'm not a math or numbers kind of guy, but I'm a bit flummoxed by the last post being post 31 of 30 :) And mine being 32 of 31.
 

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