Synthetic oil in older cars, what's the real story

[Clevy]

Originally Posted By: JohnnyO
Originally Posted By: Clevy
Its not zinc that fouls cats,its the phos isn't it.
Please correct me if I'm wrong.

I've read several times that it is the zinc, aka ZDDP. Most HM oils have at least a little more ZDDP. Maybe the P stands for phosphorus. I am not a petroleum engineer and I did not stay at a Holiday Inn Express last night.


Hehehe.
Yeah. If you dig a little deeper you'll find that its the phos that fouls the cats not zinc,and elevated zinc on its own isnt as effective as zinc and phos(zddp).
And in reality zddp doesn't foul cats unless the engine is an oil burner.
But today's oils use other compounds instead of zddp for the anti-wear agent so its not even an actual issue,flat tappet cam or not.
Zddp was used because it was cheap,today's oils have substituted other compounds in place of zddp but they cost more,so the oil costs more. And once the cam is broken in extra zddp isn't even really needed anymore.
And if you researched it back in "the day" oils didn't really have a whole lot more zddp then they do now. Its a myth that just keeps getting retold and people believe it.
And if using a 40 grade the zddp limits don't even apply anyways,just thinner grades have restrictions,the 40 grades,hdeo and most others are well over 1000ppm zinc and phos,so the whole zddp dream can e had by using a 40 grade.

 

[JohnnyO]

Originally Posted By: snowflake
any name brand synthetic will have enough zinc for most stock motors with a flat tappet.

Maybe, however (I've been here a long time, I just don't post much lately) M1 tends to show a little higher iron compared to most oils AND my daughter has a Jeep and Jeep engines also tend to throw off a lot of iron on UOA's regardless of oil (enough that you wonder how there is a block left after a few years), ergo in my humble opinion M1 is not a good match for Jeep engines. I say the same thing on the two Jeep boards I belong to and advise a HM oil on the older engines. Also my daughter's Jeep is a 2.5L TJ with a 3-speed automatic, no OD, 4.11 gears, 178,000 miles, and she got a new job about a year ago which is 20 miles each way down the Interstate, and she's usually running late which means the poor little Jeep is screaming down the road at speeds and rpm's that Jeeps aren't meant to do.

I change the Max Life 10w-30 and PureONE filter every 3000 miles and it looks like tar. Jeep has an Airaid CAI, full Banks header and exhaust, and she is known as Leadfoot by the TSA guards at the airport because they hear her coming from quite a ways away. That's my baby.

 

[snowflake]

Originally Posted By: JohnnyO
Originally Posted By: snowflake
any name brand synthetic will have enough zinc for most stock motors with a flat tappet.

Maybe, however (I've been here a long time, I just don't post much lately) M1 tends to show a little higher iron compared to most oils AND my daughter has a Jeep and Jeep engines also tend to throw off a lot of iron on UOA's regardless of oil (enough that you wonder how there is a block left after a few years), ergo in my humble opinion M1 is not a good match for Jeep engines. I say the same thing on the two Jeep boards I belong to and advise a HM oil on the older engines. Also my daughter's Jeep is a 2.5L TJ with a 3-speed automatic, no OD, 4.11 gears, 178,000 miles, and she got a new job about a year ago which is 20 miles each way down the Interstate, and she's usually running late which means the poor little Jeep is screaming down the road at speeds and rpm's that Jeeps aren't meant to do.

I change the Max Life 10w-30 and PureONE filter every 3000 miles and it looks like tar. Jeep has an Airaid CAI, full Banks header and exhaust, and she is known as Leadfoot by the TSA guards at the airport because they hear her coming from quite a ways away. That's my baby.

Noted on the jeep, however this engine isn't a jeep, its a Datsun Pick Up, which I would imagine is quite similar in design to my Isuzu Amgio's 2.6, for which the 10w30 M1 HM has made that motor run like a dream and even minimized a front crankseal leak

 

[PDX_Matt]

Originally Posted By: expat

"I have heard this from a lot of places, not just about the 620 but older cars in particular. Synthetics are supposedly "thinner and more slippery" causing leaks in older cars."

I think a 10w-40 synthetic is just about as thin as a 10w-40 conventional.

How do you intend to use this truck?
How often (time, mileage) do you plan doing oil changes?

That 2 litre OHC Datsun was a pretty robust, low stressed engine,
I had one.

It will be driven a few days a week. Planning on roughly 5000 miles per oil change, maybe more.

Also I forgot to add in the original post, but I used Mobil 1 10W-40 High Mileage. Been running this oil for a few days now and haven't seen any leaks develop so far (knock on wood).

This truck is also a "non-catalyst" vehicle and because of such does not have a catalytic converter.

 

[901Memphis]

Originally Posted By: JohnnyO

I change the Max Life 10w-30 and PureONE filter every 3000 miles and it looks like tar.


I hope your referring to the thickness of the oil because tar colored oil may still be serviceable and you can't condemn motor oil based on color.

A smooth flowing tar colored oil could still have plenty of life left. If its draining out very slow that's another story.

 

[Zaedock]

I agree on the Mobil 1 in Jeeps (non-HM flavor). Historically they are not a good combo. I've always suspected the timing chain assembly to be the source of iron in these engines. I also run a 2.5L in my trail Jeep, turn 600 lbs of tire/wheel, have a silly crawl ratio, roll many times a season and run 5W30 Quaker State syn. I'm on a two year change interval and have managed single digit wear numbers - with SM/SN levels of ZDDP.

 

[Clevy]

Originally Posted By: Zaedock
I agree on the Mobil 1 in Jeeps (non-HM flavor). Historically they are not a good combo. I've always suspected the timing chain assembly to be the source of iron in these engines. I also run a 2.5L in my trail Jeep, turn 600 lbs of tire/wheel, have a silly crawl ratio, roll many times a season and run 5W30 Quaker State syn. I'm on a two year change interval and have managed single digit wear numbers - with SM/SN levels of ZDDP.


Isn't that 2.5L a chev iron duke though

 

[2000RX300]

Originally Posted By: 901Memphis
It's a myth that won't die...


To the OP, when people change over to a synthetic oil and nothing negative happens, they tell you that YOU will not have a problem either. That is not always the case. They are not helping anyone by saying that. I was told the same thing when I wanted to stretch out my OCI's and I had a completely different (negative) experience. Then I was told that it would get better if I kept using it. It never did.

It was a different vehicle than yours, different amount of miles, etc. I can't speak for your vehicle. Eventually I switched back to the same conventional oil I had used for its 1st 100k miles of life and it went back to how it was before the switch. It never consumed oil again and I stuck with the oil that got me that far.

Let us know how you make out.

 

[Zaedock]

Originally Posted By: Clevy
Originally Posted By: Zaedock
I agree on the Mobil 1 in Jeeps (non-HM flavor). Historically they are not a good combo. I've always suspected the timing chain assembly to be the source of iron in these engines. I also run a 2.5L in my trail Jeep, turn 600 lbs of tire/wheel, have a silly crawl ratio, roll many times a season and run 5W30 Quaker State syn. I'm on a two year change interval and have managed single digit wear numbers - with SM/SN levels of ZDDP.


Isn't that 2.5L a chev iron duke though



Negative. Jeep started using their own AMC designed 2.5L (150cid) in '84.

 

[JohnnyO]

Originally Posted By: 901Memphis
I hope your referring to the thickness of the oil because tar colored oil may still be serviceable and you can't condemn motor oil based on color.

Yup, black as coal though. The oil gets the snot beat out of it and typically I add two quarts over 3000 miles. It holds four.

 

[JohnnyO]

Originally Posted By: Zaedock
I agree on the Mobil 1 in Jeeps (non-HM flavor). Historically they are not a good combo.

That's what I tell people on the Jeep boards. If you want to use Mobil 1 in a Jeep then use HM Mobil 1 even if it doesn't have high mileage. Although personally I've gotten better UOA's with PP than M1 in every one of my family's vehicles where I've compared them (this totals 7 counting my parents' cars and my company car). Never tried a full syn in the Jeep. UOA's on Rotella T-5 and Max Life were both good, although it burned the Rotella at an alarming rate. I added four quarts over 3000 miles and it only holds four quarts so it's no wonder the UOA was good. Max Life will burn two quarts over that span.

 

[FZ1]

More likely to leak with syn.

 

[PDX_Matt]

Originally Posted By: FZ1
More likely to leak with syn.


What facts do you have to backup that claim?

 

[FZ1]

Xperience.

 

[Doug Hillary]

Hi,
PDX_Matt - There will of course be many answers to your question, some good some bad and probably all based on various experiences

IMHO it will depend on what diet of lubricants were used previously and for how long. All modern lubricants that tend to clean better can be a cause when the engine has always been on lubricants of perhaps old and dubious quality!

With drive line components its a little different. Converting older axles and gearboxes need care as the "petroleum based mineral lubricant deposits can be dissolved by synthetics and other lubes causing seal leakage and lubricant loss."

Eaton proved this in the 1990s and of course it has a lot to do with the variable quality of lubricant standards in place and the type of AW and other additives in use in the past

 

[2000RX300]

Originally Posted By: PDX_Matt
Originally Posted By: FZ1
More likely to leak with syn.


What facts do you have to backup that claim?


PDX_Matt, check out my experience on the previous page. It does happen...

 

[antiqueshell]

The odds are good that using the higher quality more detergent intensive synthetics will lead to leakage in older vehicles especially those that use older style gaskets and seals. Others are correct on this. Newer, post 80s vehicles, even with high mileage are a safer bet with synthetics.

Unless you want to change out seals on that old truck stick with good quality dino oil.