Does the chart you posted contain information on what is the optimum operating temperature for a 500 V8 in the summer with the a/c on and the outside temp. @ 115 in the shade? I am guessing that the car is operating in 130 degree air in the blazing, unrelenting sun on the black top in Phoenix, where I unfortunately now live. When I lived in San Diego, I never even turned on the a/c. The only car I ever owned that operated properly in extreme heat, was a 1975 Cadillac Eldorado with a custom made(read longer than stock and 4 full rows thick) together with the stock fan which was rigid not a clutch fan that only flexed at high speed. This 500 cubic inch engine moved that 5000lb behemoth off the line even with drag racing corvettes and stayed with them til past 70 mph where I would back off the gas. I drove this car dozens of times to Las Vegas and never got less than 20 mpg. There was one long hill leaving Las Vegas, where you were cautioned to turn off the a/c or risk overheating. The first time I encountered this hill, I turned off the a/c and opened the windows like the sign said. It was like someone put hot torches in the windows, so I turned the a/c back on and blasted up this 10 mile hill past all the slow overheating, probably some Mercedes there also and the gauge never moved off normal. Never bothered to ever turn off the a/c again. Drove that car with over 150,000 miles until it was stolen.(By the way, it was a convertible). If I drove my present car this way, it would MELT! I had an Olds Tornado with a 455 ci engine that lost timing chain on interstate 5 in San Diego at 65 mph. Drove it back home and put in a used chain from one I had sitting on the floor and drove that car for years before I finally sold it. The owner took that motor out and put it in a racing boat. Right now I am debating taking off or not the timing cover to replace the lower guide rails. Don't like the idea of removing head bolts, etc. Boy do I miss Detroit iron when it was Really engineered like no other car in the world. Not just words. I hardly ever changed the oil in any american car I ever owned and they ran forever, and on cheap Pennzoil, not synthetic or Castrol at $2 a quart! I had one Cadillac V8 so sludged up, that when I transplanted it to another car, I spent a half day cleaning out the sludge, but it ran great. I drove that car for years also until it was destroyed in one of those 8 car pileups on the freeway in LA. And lastly, I had another Cadillac V8 that ran out of water on the way to Las Vegas and stopped running because it was so hot and out of water. When it cooled down, I filled it up with water and drove it 50 miles to the nearest town where I could find nothing wrong. I later learned that this particular car used a gallon of water a day, which I didn't know until it ran out of water in the desert, so for the next 50k miles, I added a gallon of water a day until my wife got tired of driving it, unlike the 380 se I bought recently from some unlucky soul who ran it too hot. My present 500sel has 275K miles on it and I am planning for it to go another 300k, so that is why I am concerned. And by the way, you said your favorite car was a 1973 Super Bug.
I retired at the age of 40 by working exclusively on rebuilding VW engines and every Super Beatle I saw had a worn out engine or blown engine at 100k miles, not to mention the front end on those cars. Sorry for the long post, just miss good old days, when American cars ran without having to have such a wonderful place such as this JUST to keep your car running. Without this website, I probably would sell my German car. By the way my son is going to buy a'94 BMW 850 with V12 and 6 speed manual trans after seeing how this Mercedes requires so much attention. Apparently they are the only German car company that can build a decent V12. I was devastated to learn that if I bought a 600 V12 my life would never be the same again.
I wanted to replace my present car with one of those until I spoke with the Mercedes dealer in San Diego and they told me they refused to sell used V12 due to customer dis-satisfaction. I didn't really believe them, quite honestly, until I met someone here in Phoenix, who spent 17K in one year on his engine alone!