Nothing on the inside of the motor has been changed or repaired.
I'm a big advocate of full-synthetic oil. Years ago I wrote a couple of reports why. I did a lot of research and posted links to everything so that people could do their own research. For a couple of years I also recommended adding a half quart of ZDDP to modern oils. I used Resoline ZDDP additive. Even though I still use higher levels of ZDDP I no longer recommend that because of some tests that have been done since and I am uncertain if it is really needed.
http://www.moddedmustangs.com/forums/96-04/292127-grade-oil-should-you-use-2.html
When I bought the car it had 65,000 miles. The owners manual says to run 5 quarts of conventional 5w30 but I have been running full-synthetic oil from day one. I ran five quarts of 5w30 full-synthetic Quaker State for the longest time then switched to 6 quarts even though it looked like I was overfilling the crank case on the dipstick (I wasn't.). Romeos use 6 quarts. I later changed to full-synthetic Mobile 1 0w30 because of the additional cold start protection. When the oil companies lowered the ZDDP content from 800 ppm to 650 ppm I started adding a half quart of ZDDP additive.
I then did the 6-quart dipstick mod and now put in 6.5 quarts to get to the full mark. Because I have a high mileage motor with larger bearing clearances due to wear I switched to full-synthetic 0w40 European Blend. Why European blend? Because it has the level of ZDDP that was recommended when our engines were manufactured which is 1000 ppm. (I'm an old dog. Even though tests are showing that the new anti-wear additives work I still want the previously recommended level of ZDDP. I just can't shake the idea that its needed. If they worked so well why do European manufacturers require 1000 ppm ZDDP?)
http://www.moddedmustangs.com/forums/96-04/542817-new-6-qt-dipstick.html
The only part of my motor that has ever been opened up is the timing chain cover. I lost a spacer on the supercharger bracket and went through a period of shredding belts. One of them cracked the timing chain cover and I ended up with an oil leak. People on the forum had been talking about how quickly the timing chain guides wore out. Most were saying to change them around 90,000-100,000 miles. Since I had 150,000 miles on the motor I told my tuner (also an engine builder) to change out everything that needed replaced when the cover was off. Nothing needed replaced. He said he couldn't believe how little wear there was on the timing chain guides. At 206,000 miles I still haven't changed them.
I noticed in your post that you have changed your timing change guides. What was the mileage? How badly had they worn?
When I was driving 20,000 miles per year I changed oil every 5,000 miles. I changed my supercharger oil at the same time. Why 5000 miles? xxx5000 and xxx0000 is very easy to see on the odometer. Oil change stations say to change oil every 3000 miles but that isn't necessary. The rule in older owners manuals was to change oil every 3,000 miles city, 8,000 highway.
Since I retired I drive around 6,000 per year so I change crankcase oil in the Spring and in the Fall and I change supercharger oil in the Spring. Cold weather causes oil additives to deteriorate faster. That is why we are not suppose to store oil in the cold. If you drive so few miles that you only change oil once per year (like my wife's Corvette) it is important to change oil in the Spring.
I do not recommend 5w20 conventional or full-synthetic oil unless you drive like grandma. It was only recommend by Ford to avoid government fleet gas mileage fines and it is too thin for anyone who drives aggressively.
