Originally Posted By: Hokiefyd
Originally Posted By: sciphi
Putting a FI engine's life in the hands of a knock sensor to save 20 cents/gallon on fuel is a false economy. Also, since it's designed to run premium, the gas mileage WILL go up on premium, negating the extra 20-30 cents/gallon it costs.
Not to argue or belabor this particular point, but the lives of most FI engines these days are in the hands of the knock sensor, even ones where regular fuel is specified in the owner's manual.
My '11 Camry 4-cylinder called for regular fuel. It would have a slight ping under certain situations, so I used premium fuel some to see if that ping would go away. Surprise: it didn't. Another surprise: mileage went up.
This demonstrates that even when regular fuel is specified in the owner's manual, and when regular fuel is used, the engines are still running at the mercy of the knock sensor. The timing is simply retarded more than it is when using a higher grade of fuel. It's my experience that many modern engines that are tightly-tuned can benefit from higher grades of fuel, even if the owner's manual calls for the regular grade.
I do strongly agree that using regular fuel where premium is specified is a false economy. As you note, the cost difference between the two is largely negated by the mileage increase. I've found that to be the case even when using premium in cars that called for regular, but specially when premium fuel is recommended in the owner's manual.
Point taken.
My old Buick LeSabre with its 3800 Series II V6 and 2.86 final drive ratio would routinely get 33-35 mpg at 60-65 mph. Best I ever got out of it was 39 mpg doing 55 mph for 15 hours. Nothing like a good old-fashioned bench seat with no bolstering for that kind of driving!
Any H or C body such as a Pontiac Bonneville, Buick LeSabre/Park Avenue, Olds 88/98, or even a Lucerne (IIRC) would be a great highway cruiser. The H-bodies tend to be a bit more spacious inside and in the engine bay than the W-bodies like the Grand Prix/Impala/Lacrosse/Regal (don't quote me about the Lucerne and Lacrosse). If one can't find a LeSabre, a newer Regal is also a good choice, as they tend to have better interiors than the other W-bodies.