.boB

The perpetual question is, how long between oil changes? How many times has that been asked? And how many differant answers have you heard?

Just for fun, I decided to do UOA's on my new Mustang and see what happens. With a new engine, I'm pretty quick to change the oil. I bought this car on Saturday with 623 miles on it, and changed the oil on Sunday. I used Penzoil 5W-30 and a Purolater Pure-1 filter.

Two months and 1500 miles later, I changed the oil again. This time I used Royal Purple 5W-30, and a Pure-1 filter.

Initially, I planned on changing it according to the factory recommendations, which was 7,500 miles. Mostly to get a baseline. But, between one thing and another, I let it run 8,340 miles and 11 months before changing it. The car did see some long distance trips - Texas and Utah. But mostly it's my daily driver and commuter when weather is questionable.

Anyway, to the point. Here's the recommendation:

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BOB: High wear and silicon are both common finds in new engines such as this. Wear is due to break-in of
new parts, while silicon is from sealers and sand-casted parts. Universal averages show typical wear from
this type engine after about 4,600 miles use. We expect your engine will look better in two or three more oil
changes, though it may not match up with averages if you stick with the long oil runs. That's not really a
problem and we don't think you need to shorten your oil use any. The trace of fuel lowered the viscosity a
little, but don’t affect anything else.
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So, the oil held up at 8K miles like a standard oil would at 4,600 miles. Not bad.

Here's some other interesting stats:

Viscosity @ 210*F 53.6 (54-61)
Viscosity @ 100*C 8.35 (8.5-10.8)
Flashpoint 360 (>365)
Insolubles 0.2% (<0.6%)

They also list a lot of metals and salts, and give you the Universal Average.

Zinc 893 (822)
Magnesium 1236 (68)
Phosphorus 795 ( 687)
Calcium 2430 (2271)
Molybdenum 132 (80)
Iron 66 (15) *** this was interesting


And there's a few other things that tell you more about the engine condition, and less about the oil condition.

Part of the issue is that you get averages, not specs for your specific oil. So you really don't know how much of the package you lost over time. What were the original/as new viscosity numbers? Or zinc? IDK. For $20, I could find out, though.

What's next? Not sure. I think I'll let it go to 10K miles, and do another UOA. We'll see what happens then. If it's much below specs, I'll let it go another 10K. But, that time I'll change the filter about half way through; which would require adding another 1/2 qt or so.


A note about Synthetic oil. AFAIK, there's only three truly synthetic oils on the market - RP, Redline, and Amsoil. A synthetic oil starts out with a synthetic Group IV base stock. All the other "synthetics" start out with Group III dino oil. They're not bad oils. But they're not synthetic, either.

I did a UOA on my Harley, using M-1 15W-50. After 2,600 miles, the oil didn't stand up very well. It lost a lot of viscosity. I'll let it stay there for 2K miles, then change to RP.

If anybody wants a copy of the report in PDF, I'll send it to ya.