The 300 SE does maybe 30, the 500 SEL about 20, the 123 the rest â€“ BUT â€“ the 126s take turns on the monthly trip to Destin to see my parents: 843 miles round trip every other month. They get to stretch their legs, best open road cars in the world. Itâ€™s important to let everything get hot for an extended period of time, I believe it prevents nagging little problems. 
I may very well be the most prolific driver on the W126 forum! I bought my car on 10-06-04 and except for the 550 miles to retrieve it from Ohio I actually didn't drive it till a month later when I made it my daily driver......and daily drive I do.
If my math is correct, from that date (11-06-04) till now (3-17-05) is a total of 131 days. I bought the car with 129,000 miles on it and now I have 153,000 for an aggregate of 24,000 miles traveled. That equates to 183 miles for each day of ownership.
For a living I buy real estate interests for private and public sector utilities and needless to say, I do a lot of traveling. The fortunate circumstance is at least 90% of that mileage is reimbursed at the rate of .405 cents per mile. I fill up nearly every other day and never go more than 3 days without doing so. I am currently in Virginia and premium fuel is at $2.19/gallon for BP Supreme and that costs in excess of $40.00 per tankful.
In anticipation of the question some of you may ask......I get between 18 and 19 MPG in my travels and my car is a 1990 560 SEL. I bought this car to replace a 1999 Cadillac Deville and I wish I had done so 10 years ago.
Well, I fill up just about every 4 days ($2.49-2.60per/gal depending what part of the island you're on). I'm getting about 295-350miles per tank (depends on highway or stop-n-go and a/c). I'm constantly back and forth around the island so miles add up quick. I'm hoping to get a motorbike soon so I can take it a easy on "my baby".  She's a 1989 560sel and had only 79k when I bought it back in 98'. Now she has 221k !! [:O]
Whoa, that's a lot of mileage you've managed to put on just driving on an island.
I guess when you say Hawaii, you mean the Big Island. Gas prices aren't too great around my neck of woods either - avg 2.30 per gallon.
By the way, I drive about 180 miles per week. I use about half a tank a week so that's about right.
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