# Royal Purple vs all others



## jeepjoint (Dec 7, 2019)

Had my 1968 400 engine professionally rebuild about 8000 miles ago. Used Royal Purple 5W 30 since the rebuild. I added Lucas TB Zinc-plus at each oil change. Only complaint is still using about a quart of oil every 2000 miles. Not too concerned, but would like to reduce the consumption more if possible. My opinion is that the rings still have not seated. 
Thanks in advance for your help.


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## pontrc (Mar 18, 2020)

jeepjoint said:


> Had my 1968 400 engine professionally rebuild about 8000 miles ago. Used Royal Purple 5W 30 since the rebuild. I added Lucas TB Zinc-plus at each oil change. Only complaint is still using about a quart of oil every 2000 miles. Not too concerned, but would like to reduce the consumption more if possible. My opinion is that the rings still have not seated.
> Thanks in advance for your help.


I would go to a 10W30 or 40. 5W seems a little light to me


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## Jim K (Nov 17, 2020)

I agree w/pontrc. 5W might be a little light unless you live in the northern realms (northern Canada/Alaska).. As for the oil consumption, well, we all have our own levels of comfort but for me, that amount of oil consumption after 8,000 miles would be outside my range of acceptable. If it's the rings it should be showing up on the plugs as being really blackish and maybe somewhat oily on the electrode.
I have a 68 428 +30 over that's fairly radical. Less than 2000 miles on the motor and it uses virtually NO oil (that's of any measurable amount). A motor using as much oil as yours seems to be, would not be acceptable to the factory when it was new, so it shouldn't be acceptable to us with a rebuilt motor 50+ years later..


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## armyadarkness (Dec 7, 2020)

Lol. I would kill to lose 1 quart every 2000. My 67 400 uses oil like it was built to do nothing else. I have a leak at the valley pan rear, but no visible rear seal or vc leaks and my plugs look great! I use synthetic blend Valvoline 10w40 and I have a Wagner PCV valve with a catch can. So, Im assuming that it's a combination of the Wagner and the valley pan? Either way, I lose at least .5 qt every other time I drive the car. I also do a lot of 3200 rpm highway cruising and put about 150 miles a week on the car.

I feel like I need to tune my Wagner better, but theres already oil in the catch can..


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## PontiacJim (Dec 29, 2012)

That could be normal for your engine. Many factors come into play, but.......

From what I read, Royal Purple is a synthetic. The clearances and tolerances of the older engines really don't do well with synthetics (*my opinion*)- unless the rebuilder assembled the engine for synthetics. If you broke the engine in on synthetics, you may have not seated the rings as well as you could have and it also depends on how you broke the engine in.

Pontiacs use a slightly larger clearance on the valve stem/valve guide and by nature will use a little oil if the heads were spec'd for stock clearances.

Make sure your PCV valve is working correctly as well as breathers in the valve cover. 

Check your spark plugs and see if you have any cylinders that show obvious oil burning.

You could first try a 10W-30 grade of your brand oil and you can also try and switch to a conventional oil, 10W-30 or 15W-40 having the zinc or use a little zinc additive and see if this improves the mileage.

I did my own pesonal test on my 2015 Hyundai Accent with the 1.6L engine. I use conventional 10W-30 Valvoline in it instead of the synthetic 20W it calls for. I tried the synthetic 10W-30 for 1 oil change - I go 3,500-4,000 miles between changes. My engine consumed more synthetic between my oil regular oil change. Went back to my Valvoline. I also live in the "hot" south and run 80 MPH back and forth to work every day, so I don't baby my car. I was getting 2,200 miles to a quart since owning the car with 30,000 miles. It began to use 1 quart for 1,000 miles. Installed a new PCV valve and mileage has gone up to about 1 qt for 2,000 miles and I have 147,000 on it now. I won't worry about oil consumption until I hit 1 qt for 800 miles - then it will be time for a rebuild.

You will read that the latest synthetics are now formulated for the older cars. They do have superior qualities over conventional oils. Seems the older synthetics, when first introduced, were not so good for the older vehicles. So there is more info/positive feedback on the use of synthetics in the older cars. But *my opinion* is the engine needs to be assembled/rebuilt with different tolerances to take advantage of the synthetics. I would not use 0-20W in my 455, but 0-20W is the "norm" for many cars made today.


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