Unfortunately, this is a multi-faceted question. So, a 1-answer fits all approach is probably missing the mark.
1- The 998 is a high to very high compression engine (depending on model and year). High compression encourages Knock or Pre-Ignition which can destroy an engine in pretty short order. (This is when the fuel ignites BEFORE the piston reaches the top of the stroke, basically trying to run backwards) Very Bad!
2- Lower octane fuels have more energy potential than high octane fuels, (contrary to popular belief encouraged by sometimes misleading advertising). So, you ask, then why do high HP engines require High Octane fuel if there is less energy contained in that fuel? Good question with a fairly simple answer. Higher compression gives you more HP but requires a lower energy fuel to keep it healthy. The increase in HP from the higher compression ratio more than offsets the loss in HP from the lower energy fuel.
So then you ask, why does a lower energy fuel COST MORE!? Another good question. Because the additive which raises Octane is much more expensive than the volume of fuel it replaces. Plus, High Octane fuel sells in much lower volume than low octane fuel. Like anything else. High volume sales usually makes the product less expensive.
So, now that I've bored you to tears. We'll move on. (That is if you've even bothered to get this far!) :roflblack:
3- In cooler weather and low load situations (like running down the highway on flat ground at a steady speed), Knock is not usually an issue. So using low octane fuel will probably give you better fuel mileage without any downside and save you some money at the pump too! Nirvana! You say! Well, not exactly.
4- If you are pulling heavy loads, climbing hills or mountains or doing anything that works the engine fairly hard. Or, if you are running in very warm to hot weather. This, plus the high compression engine are most certainly going to put you into situation #1- Knock or Pre-Ignition mode.
In a normal engine you would be risking your motor. But!
5- The Spyder, being a modern engine, has a computer which monitors and regulates cylinder head (combustion chamber) temperature. This is one reason it is so important to put Thermal Paste (NOT Anti-Seize) on your spark plug threads! If the computer senses temperatures which could cause Knock or Pre-Ignition, the computer takes steps to reduce those temperatures. Kind of like an engine protection Nanny. To do this the computer retards ignition timing. That works GREAT for cooling down the combustion chamber and preventing the dreaded KNOCK! But it also reduces power and MPG. The more the computer has to retard ignition timing, the greater the loss.
So, the hotter, harder and more loaded the conditions, the more you need higher octane fuel.
Will the Spyder run on just about anything? Yes.
Will it have more power and get better fuel mileage on low octane fuel? Under the right conditions, probably.
Will the Spyder have more power and get better fuel mileage with high octane fuel? Absolutely! Under any condition that would otherwise cause knock (which are many).
Will your Spyder ever experience engine destroying Knock or Pre-Ignition with low octane fuel? No. The computer pretty much takes care of this at the expense of power and MPG when necessary.
Should you run 91 or higher octane? In my opinion, yes you should.
Now, about the oil you're using! :roflblack:
hyea:
