Originally Posted by greenie
Check the valve covers for a leak - the smell could be the oil dripping down on the manifold. It's a common issue with these cars, and is an easy fix at the dealer. Mine developed the leak at around 5,000 miles. I started to notice a burining smell every time I pulled into the garage.
Greenie is right, sometimes burning oil does smell like burning rubber. That may very well be your problem.
To answer the break in question, 30 years ago I came across a synthetic oil that sold for a fraction of the price of Mobil1. On the can it recommended not using it until the new engine was adequately broken in.
Since I wanted to use it in my then new 1979 280 ZX, that I had only put a few 1000 miles on, I wrote to the company and asked them at what mileage should I start using their product. They wrote back and told me to hold off until I had put about 7k miles on it. Now that impressed me since they didn't just tell me to go out and buy their oil right now.
As it turned out, the following summer I took my car on a trip to Wisconsin, and on the way up I drove the Interstates very sedately, stayed in 5th gear most of the time at close to the speed limit and got about 25 mpg.
On the way home the car rolled over 7k miles, so I took secondary roads, and drove my car much harder, stayed in the lower gears longer, and up shifted and down shifted much more, and got 27 mpg. The car seemed to just loosen up and felt more responsive than it ever did before.
So I don't know if that's the "magical" number or not, but that was my experience.
Of course now the cars come from the manufacture with synthetic oil already in the crankcase, so maybe the "break-in" mileage theory has changed as well.
