Is It Ok To Use Full Synthetic Oil Such After Long Use Of Conversational Oil?

[blackandgold51]

Got a 454 Carburated V8 in a 1983 C20 Turbo400.

As of now it has 1040 conventional oil which the next oil change will be switched to 5w40 .

Is it ok to use full synthetic? Also engine has over 149000 miles

 

[YOUNGBLOOD13]

It is ok to use synthetic, but I would recommend a high mileage version, with seal conditioners. It is more prone to leak than the dinosaur oil. Be sure to monitor oil consumption for a little while.

 

[mrk5]

I use Amsoil either the XL or Zrod versions because it has added zinc which is supposed to be good for the older flat tapet cams. Both motors I use that in are old and ran conventional oil before.

 

[dyeager535]

As of now it has 1040 conventional oil which the next oil change will be switched to 5w40

5W40? Why?

So much theory and opinion on oils. Synthetic *IMO* is still too expensive for what you get. It may work better, but I have yet to see any testing that actually shows wear at the bearings over X number of starts, or hours run time, etc., that would provide apples to apples comparison that means something. Edit: I'm basing this off of cost. I can still change my oil twice for the cost of one fill of synthetic, and synthetic manufacturers recommendations since these trucks do not have a recommendation from GM, tell you to stick to the manufacturers oil change interval anyway. I know there is some oil marketed for extended oil changes (or was, didn't see it last I checked), but again, unless time is a real issue, I don't see the cost benefit.

I don't believe any of the manufacturers say that switching between the two is an issue, anecdotal evidence being just that. If the engine leaks, it's either a bad design or bad seals, not the oil.

 

[sweetk30]

fyi almost all oil for years now is semi synthetic mix .

and your older gas engine was not made for 5w based oils . stick to the 10w weight .

i can tell you tho years ago i swapped from 5w-30 to 10w-30 on a tbi 350 engine designed for 5w-30 oil and i noticed a slower crank and inital start up speed . swapped back to the 5w-30 and was back to normal . and the oil cap on that gm long block engine showed 5w-30 oil grade is spec .

also you live way down south . you dont need the 5w for cold starts . us northers guys might notice it in the winter more than you will .

 

[mrk5]

I'm running 10w40 Amsoil XL in the 454. 10w30 Amsoil Zrod in the 327 and 350.

I was thinking the factory recommendation on the TBI350 was 5w30.

 

[76zimmer]

Start having your oil lab tested, then switch to synthetic and have that first change tested. That will tell you what you are gaining with synthetic

 

[HankScorpio]

Run what you want but I have personally run 3 GM and 3 Jeeps to 250,000 miles with conventional oil. Valvoline or Castrol, whichever was on sale, every 3000 miles. None of them were retired due to blown engines, I still drive 3 of them. Synthetic may be better in the lab but for the price of synthetic on an engine with 150,000 miles I don't see the point.

 

[shady]

Every time I've went to synthetic from conventiinal in something I noticed more engine noises (particularly on start up), oil consumption, and (in the squares) shooting the blues.

All we're high milage versions. I've since went back full conventional and I'm staying there.

 

[diesel4me]

I have used only "regular" oils in all my vehicles and small engines..
Not (just) because I'm cheap,but because I don't see them gaining anything using synthetics..

My theory is they were run so long with conventional oils ,that its rather late to switch to a synthetic,and any sludge that has accumulated in the engine may get loosened up and circulate thru the engine..an old engine that leaks or uses some oil will leak worse and consume more of the thinner viscosity synthetic too ..

After so many years and miles,any "damage" has already been done,and synthetics wont cure anything ,the fact they cost more is a discouragement also...if I had a new vehicle I'd break it in on conventional oil ,then go with full synthetic from then on,it would be worth it in that case.

I did buy a 5 qt. jug of Mobil 1 15W-50 to use in my John Deere riding mower's transaxle,which is what most repair shops put back in them,rather than the 10W-30 factory oil--these hydrostat transaxles are noted for being weak and failing early,so I wanted to dump out the original fill and replace it with the thicker synthetic,it had 450+ hours on it and still worked fine,I just wanted to keep it that way as long as possible..

I only needed 2 qts,but the jug had 5 qts,it was much cheaper to buy the bulk jug at Walmart than individual quarts (3 qts would cost as much as the jug did!)...
I had been tempted to put the rest of the Mobil 1 15W-40 in my 6.2,but I do not see it rated for diesel use going by the API ratings on the jug,though the Mobil 1 web page states it is suitable for "all gasoline,diesel,and turbocharged engines"..

But it may not keep soot in suspension like 15W-40 diesel rated oil...but if I mixed 15W-40 diesel rated oil in with it,maybe that would be enough to keep the soot in suspension ?..I've read it takes only 1-2 qts of synthetic oil added to conventional,to reap 80% of the benefits VS a full crankcase of synthetic,hence the fact "semi-synthetics" are now popular..


I'd like to go with a lower viscosity in the winter to aid cold starts,but I'm hesitant to use this in my 6.2..it leaks and synthetic might eat thru what I've used to patch my rusted oil pan..
I will probably go with a 10W-30 conventional oil rated for diesel use like Rotella T for the winter..

If I had a higher mileage 454 down south where it wont dip much below 32 degrees ,I'd stick with a fairly thick oil like 20W-50 or SAE 30,you could use 15W-40 diesel rated oil too,which has more ZDDP for flat tappet camshafts...

I've seen quite a few older Chevy engines around here that lost cam lobes recently,the newer oils don't have enough protection for flat tappets--one '68 Chevelle a friend has with a 327 lost 3 lobes on a new Edelbrock cam in less than 5000 miles using Castrol Syntec oil,10W-30,and he did break it in properly,he's built engines for decades,said he never had a cam flatten so fast before--didn't know whether to blame the cam itself,or the oil..

 

[black dawg]

Switching to synthetic wont cause any issues. I run synthetics in all of my stuff anymore, just because I like the 5w40 weight. No cranking speed issues and easy starts regardless of temperature. I have noticed oil consumption go down after a few changes, always expected it to go up. I used to always change oil at 3k, now I do it at 6k or more, so not worried about cost of oil.

 

[imiceman44]

5W40? Why?

So much theory and opinion on oils. Synthetic *IMO* is still too expensive for what you get. It may work better, but I have yet to see any testing that actually shows wear at the bearings over X number of starts, or hours run time, etc., that would provide apples to apples comparison that means something. Edit: I'm basing this off of cost. I can still change my oil twice for the cost of one fill of synthetic, and synthetic manufacturers recommendations since these trucks do not have a recommendation from GM, tell you to stick to the manufacturers oil change interval anyway. I know there is some oil marketed for extended oil changes (or was, didn't see it last I checked), but again, unless time is a real issue, I don't see the cost benefit.

I don't believe any of the manufacturers say that switching between the two is an issue, anecdotal evidence being just that. If the engine leaks, it's either a bad design or bad seals, not the oil.

I tell you why I switched some of my vehicles to synthetic 25 years ago.
Dyno oil once run in an engine to operating temperature starts to oxidize which turns it acid.
In 3 months it becomes acid enough to start eating bearings.
That's why they recommend changing the oil at 3 months regardless of the miles if you don't run it enough.
Synthetic oil doesn't have that problem and they can run 8000 miles at least the ones I used back then Castrol magnatech.
I changed the oil once a year on those vehicles that didn't run much instead of 4 times a year.
And they did start easier throughout the year too.

 

[imiceman44]

On a similar note my big rig gets the conventional oil because I have to change it in less than 3 months based on mileage

 

[dyeager535]

Dyno oil once run in an engine to operating temperature starts to oxidize which turns it acid.

What's lacking from this is real-world, credible testing as far as I am concerned. Every oil out there, synthetic or non, is going to perform differently because every manufacturer that isn't relabeling someone elses product, has different chemistry.

I don't really have the inclination to go compare the total base number of a variety of oils (which is the measure of ability to resist acidification) but I'm willing to bet some are "better" than others. Can't find a comparison of synthetic to conventional (which makes me question if there is any) but I did find the Petroleum Institute showing an average TBN of 8 http://www.pqiamerica.com/TBN.htm, while Amsoils comparison of various synthetics shows some of the synthetics being at 8 as well. https://www.amsoil.com/newsstand/articles/what-is-total-base-number/ The mechanism to form acid (water and combustion byproducts) doesn't seem to be dependent on the oil.

Even Mobils "guaranteed 15000 mile change interval" has a million notes about not exceeding new car manufacturers oil change intervals, and/or oil life monitor warnings, even though the Magnuson act would force the vehicle manufacturer to PROVE the oil was the cause of a failure before they could deny warranty claims.

 

[imiceman44]

What's lacking from this is real-world, credible testing as far as I am concerned. Every oil out there, synthetic or non, is going to perform differently because every manufacturer that isn't relabeling someone elses product, has different chemistry.

I don't really have the inclination to go compare the total base number of a variety of oils (which is the measure of ability to resist acidification) but I'm willing to bet some are "better" than others. Can't find a comparison of synthetic to conventional (which makes me question if there is any) but I did find the Petroleum Institute showing an average TBN of 8 http://www.pqiamerica.com/TBN.htm, while Amsoils comparison of various synthetics shows some of the synthetics being at 8 as well. https://www.amsoil.com/newsstand/articles/what-is-total-base-number/ The mechanism to form acid (water and combustion byproducts) doesn't seem to be dependent on the oil.

Even Mobils "guaranteed 15000 mile change interval" has a million notes about not exceeding new car manufacturers oil change intervals, and/or oil life monitor warnings, even though the Magnuson act would force the vehicle manufacturer to PROVE the oil was the cause of a failure before they could deny warranty claims.

We

What's lacking from this is real-world, credible testing as far as I am concerned. Every oil out there, synthetic or non, is going to perform differently because every manufacturer that isn't relabeling someone elses product, has different chemistry.

I don't really have the inclination to go compare the total base number of a variety of oils (which is the measure of ability to resist acidification) but I'm willing to bet some are "better" than others. Can't find a comparison of synthetic to conventional (which makes me question if there is any) but I did find the Petroleum Institute showing an average TBN of 8 http://www.pqiamerica.com/TBN.htm, while Amsoils comparison of various synthetics shows some of the synthetics being at 8 as well. https://www.amsoil.com/newsstand/articles/what-is-total-base-number/ The mechanism to form acid (water and combustion byproducts) doesn't seem to be dependent on the oil.

Even Mobils "guaranteed 15000 mile change interval" has a million notes about not exceeding new car manufacturers oil change intervals, and/or oil life monitor warnings, even though the Magnuson act would force the vehicle manufacturer to PROVE the oil was the cause of a failure before they could deny warranty claims.

Well I don't know what to make of this but the test you referred to was in 2013, this test was I believe this year talking about the overall performance.
Take it with a grain of salt.
https://www.chicagotribune.com/clas...enefits-autotips-0608-20170607-story,amp.html

 

[dyeager535]

Take it with a grain of salt.

Thats what I mean. Everything stated doesn't provide the empirical tests. AAA test was apparently done, but I don't know all the tests. Was it X wear over Y time?

I would like to see REAL engine tests with this stuff. Put them in a vehicle or on a dyno, and run them under identical conditions that are representative of "normal" use. Tear them down and measure wear. It's that simple.

FWIW the diesel engine oils have nearly double the TBN of gas oil, but they require it. If acid was the only concern with time-based change interval, since gas engines don't contaminate oil like diesels, one would *think* a 10W-30 diesel oil would increase the time span on oil change intervals when used with a gas engine.

Even on the manufacturers websites (at least Mobil and Castrol, that I could find) they don't reference acidification resistance as being one of the oil benefits.

If in the real world I'm reducing wear by a made up example of 2% by going synthetic, but it costs me double, and I could just change the conventional a bit more often to achieve the same wear, then synthetic does nothing for me. My truck might see 3k a year, and I change it twice with conventional. Only that 15K Mobil oil recommends a yearly oil change, even at that it's too pricey to justify. All the rest of the synthetics seem to stick to the 6 month change interval.

My 2015 car (10/100 warranty) calls for a 7500 mile oil change interval with conventional oil.

There are so many wildly differing commentaries on this topic, that I remain skeptical that in actual application, synthetic matters for most people/engines. It's pretty obvious that synthetic, under lab testing, reduces wear over conventional. I don't think that is arguable at all. But how does that apply to my crank bearings the 100 times a year the truck is started? How does it affect the roller lifters? Whats the cylinder wear? If there is testing out there that actually compares that stuff, I'm all ears. I like numbers. I have no idea what it costs the manufacturers to make synthetic vs conventional. If it's not double, then that definitely brings into question the advertising claims.

 

[frankin5]

None of my factory recommended oil changes are under 5000 mile intervals. Using synthetic I go more 8000 to 10000 with no problems,

 

[mrk5]

I always figured people went synthetic due to intervals. I like it in my "hobby" vehicles for the reasons @imiceman44 mentioned, not worrying about the acidity thing. I probably get 3000 miles max a year on those trucks.

And like I said, I like the added zinc. I don't have any empirical evidence; I guess I buy into the "hype" and it makes me feel better. I might feel differently if I was paying for multiple synthetic oil changes in a year.

 

[dyeager535]

I always figured people went synthetic due to intervals.

That's part of the issue when I looked into it due to the ~2x cost of synthetic. Other than the 15k mobil, none of them seem to recommend anything more than 6 month interval, nor will they recommend you increase the mile interval.

With a vehicle that sits much of the time, six months and 1500 miles doesnt help.

 

[K5wrench]

I used to be anti synthetic.
Then i moved to the top of a mountain in Wyoming...

Rotella 5w 40 synthetic t6 winter.
Rotella 15w40 synthetic t6 summer.
Every 3000 miles.
Delco filter with every change.

You can definitely tell the difference at minus 40 cranking the 6.2 over.
Even better to run the propane block heater over night.

Havent noticed any leaks after switching
From Dino oil.
Zero oil consumption.