<br /><br />I also like to run a tank of the good stuff through all my vehicles once in a while.<br /><br /><br />H.
<br />45 gallon tank. 
Yes DJ, this 225 Promax says no less than 91 Octane. It is a 2000 model and has had the Mercury upgrade done to it when they did the rebuild.
I may be wrong so feel free to correct me, but I was told by a "person in the know" at a filling station that mid-grades are actually a mixture of regular and premium as most stations only have two tanks. There may be four or five fills but there's really only two types of gasoline in the ground at the station. If you get poor performance from regular, ask the station if they adulterate their gasoline with ethanol. If so, find someone else, who doesn't use ethanol.<br />Now for what I do know is accurate, from several reliable sources. Octane is a rating of heat energy. The higher the rating the less the heat energy. Thus premium grades have less heat energy than regular does. Perverted, as it seems, it costs more, gives less energy and therefore lower mpg, all things relative. The higher the octane rating the less susceptible the fuel is to pre-ignition or spark knocking. Pre-ignition is caused by the fuel/air mixture combusting from the heat of compression and residual heat within the engine. Just like a diesel. That is why high performance and high compression engines generally require premium fuels. The higher compression and operating temperatures of these engines cause them to pre-ignite lesser grade fuels.<br />And the previous posts were wise when they recommended using the lowest grade fuel possible. If you don’t encounter performance problems, using the lesser grades will save you money. You will save $$$ by the lower cost and by the greater mpg due to the greater heater energy.<br />As for the Verado requiring Premium, is that super/turbo-charged? That would explain why. The forced induction in effect raises the compression ration. Not to mention the heat generated by the compressor itself, that’s why a lot of cars and trucks have an intercooler.
I don't know what all they did in the upgrade.<br />They reset the CPU, did something to the timing on it and did something else to require it to use 91+ octane.<br />This from Mercury race division.<br /><br />This is a new re-man'd powerhead from Mercury and they gave me special instructions on breaking it in, and one of them was 91+ octane without any alcohol.
I will tell you this, I hauled gas/fuel for a few years and when I loaded, I loaded 3 products of gas, regular, mid-grade, and premium.<br />Put into different compartments of my tanker and dropped in 3 different holes in the ground.<br /><br />Maybe some that do that, but it's not the norm.
