Be careful with zinc, if your engine cylinders are no sealing perfectly and some of that oil sip thru into the combustion chamber it will go unto your catalytic and it will clog them. That is the true reason oil company did away with zinc additives. By the way, I am not an expert in oils...........

 

Chemical engineers in oil companies already balanced the oil additives for each application the oil was designed for, & you will not see any major oil company selling any oil additive, because their oils don't need any,,, as the matter of fact no good quality oil needs any additive, if it does, then you want to stay away from that oil.
ZDDP (zinc/phosphorus) is already balanced in right amount in each given oil,
There is no zinc additive in market that will improve an motor oil wear quality by adding to motor oil, it will just simply rouin it's balance of ZDDP to say the least,
Some mechanic claiming such a thing that an additive will improve an oil wear quality, is just blowing hot air,, Do You think he has a better testing & research facility than a major oil company that invests millions into research,?
All additives that claim to make improvement in any oil are %99.9 snake oil,!!
Don't waste your engine & money on them,,
Different oils make engine sound different, synthetic oils are usually louder than conventional oils, & has nothing to do with engine running better or worse,,
If an engine is running fine with an oil it doesn't mean it's providing best protection,
It just means it is providing adquet protection in normal conditions,,,
Keep in mind all oils aren't providing same protection, & just having a right weight oil doesn't mean it will protect the engine as good as another,
Also best wear protection doesn't have anything to do with oil being synthetic or conventional , or being expensive or lower in cost,,
You really don't need a very high zinc oil to protect flat tappets, if you start with an oil that has at least 900-950 ppm by the time you change it it will still have at least
800-850 ppm, and it's more than enough to protect any flat tappet,,
There are lots of very high ZDDP oils in market that aren't that good , so don't be fooled with them,,
Lot of members here prefer using Rotella, I personally don't , because it's designed for Diesel engine, which mostly run in much lower RPM's than most gas engines, & has a lower termal breakdown value compared to most high quality gasoline oils,,
Anyone can choose what they prefer,
I use Mobil1 0w40, it has 1000/1100 -zinc/phos content & at start when engine is cold (and most of wear happens). flows much better than other w40 oils,,
It can last upwards of 6-7k miles if mostly fwy miles , but I change it at 3k, because cost of oil & filter is nothing compared to what you spend on gas at those miles, & it's not worth trying to save money by running the engine oil for longer in old school design of rover V8, this engines like shorter oil changes better.

 

well you sure wrote it like you are the expert! talking about "true reason," LMAO. where did you hear that?


It could be true and also common knowledge but this is the first time I'm hearing a lot of this stuff

 

It is very true, oil companies started reducing ZDDP in early 80's so much by request of car manufactures/API & government to extend life of cat converters (without replacing it with other EXTREME PRESSURE agent) that it killed a lot of flat tappet engines , specially the ones with higher performance cams,,
But eventually raised ZDDP level again, but not as much,,,
Now most oils with lower ZDDP level use other EXTREME PRESSURE agents,,
Low zink level in oils inforced by API now, only applies to 30W or lower viscosity oils. Higher viscosities & some SL rated oils can still have much higher ZDDP levels..

 

I've been using Mobil 1 10w-30 with a Mobil 1 filter for the past 2 oil changes. I change it out every 3k miles or every 6 months because I don't drive my disco that much. It doesn't leak between oil changes. Next time I will use Mobil Super 10w-40 with a mobil 1 filter ($2.59 a quart at O'Reilly).

 

In a Disco, this is a questionable choice because 10w-30 oil is only good up to ~85 deg F ambient temperature. Unless you live down in the city, I'm betting you see temps over 85 F all summer long.

Personally, I ran Rotella T one time and right after I filled the engine with it, with the first crank it sounded far worse than the dirty M1 I had just drained. I barely made it to 3000 miles because of all the valve and lifter noise. I swapped it to M1 Turbo Diesel Truck 5w-40 and it sounded like a new engine.

About two weeks ago I changed the oil (M1 TDT) and added Prolong, and I am blown away by how quiet and smooth the engine is now. The initial clatter right after start is gone. Right after I changed it, I stopped at a stop sign, and I thought the engine had died it was running so smooth.

They sell heavily discounted gallons of Prolong at Amazon, and I will be buying one before my next oil change.

 

It's usually 70*F here +/- 10*F depending on the time of year. Sometimes in the summer it reaches 90 but that's rare. Next oil change will definitely be 10W-40 or even 5W-40. My rover mechanic says that he adds less than a pint of 75W-90 to leaky rover V8s as an oil stabilizer. He has gotten good results with it (especially on rear main seal leaks). Has anyone ever tried this?

 

where else can you find Prolong? On a shelf, that you know of? Their website lists Autozone and Oreillys, but I've never seen it. I guess I could call and ask if they will order it.

 

I got mine at Advance about two years ago. They had it on clearance, so I bought 3-4 of them to use in my Dodge van that has a weird vibration that the Prolong cures. Shortly after I bought it, I found a post where people were saying those additives didn't help if you were running good oil, and I had recently switched to full synthetic in all my vehicles. Also, I haven't been driving the van much for the last few years, so they've been on the shelf. I pretty much forgot about them.

Years ago, when I first starting using it, I had just changed the oil on my van. It had only 40k miles and had this weird, subtle low end knocking vibration. So, I cranked it up, and poured the Prolong in. Almost immediately the noise went away. I used it for many years while the van ran ~80k miles. When I got the Disco, I kept the van as a tertiary vehicle, but quit 'prolonging' it. And since I was running top shelf oil, I didn't bother 'prolonging' the Disco.

But I am completely sold now.