Join Date: Sep 2015
Location: St. Petersburg, FL/USA
Well, you're half-right with your opinions Knifemaker, although some of them are less than factual here. First, a motorcycle compression ratio of 10.3:1 IS relatively high for an older street bike - especially for one more than 10-years-old. Today, a number of coolant/oil cooled street bikes run 10 to 12:1 compression ratios to boost horsepower. That's because air/oil-cooled bikes lack close internal tolerances in valve and pistons for higher compression ratios. Fortunately, coolant/oil cooled bikes, like Vulcan's, do not have that old-school cooling problem i.e., requiring 'strategic cool-downs' on a run.
Gasoline combustion in a motorcycle engine is a relatively simple and dirty matter. I agree, that even the cheapest 87-octane grade at the local Quick-Mart will get most bikes to run alright for a good while. And yes, nearly all manufacturer's make commercial motorcycles to run on the cheapest gasoline available to meet EPA MINIMUM STANDARDS for sales i.e., tolerating 87-octane blends. Gasoline is like food for humans in a way. You can eat the cheapest foods and still live for a good while. But performance for both eventually progressively suffers due to various kinds of deposits, buildup, and gunk which robs performance, slowly yet surely. No law against using the cheap stuff.
Informed reading does help in understanding this little researched topic of gasoline types. Motorcyclist (2015) magazine, the June and July 2015 editions, had some great articles titled: Gasoline 101. In Part 1: Origin, Additives, and Octane, Ari Henning, reported that after refinement, base gasoline types are simply shared among all brands. The important part is what is added by design to each base stock gasoline by a company i.e., detergent additives in top-tier name fuels are at minimum 2.5 times higher and free of metallic additives for all grades of gas, including 87-octane. Higher octane gas can prevent unwanted detonation (knocking), if that becomes a problem, on regular unleaded (87-octane) gas. The best reason, however, to use higher octane fuel though is for keeping the internal parts of an engine clean. For example, Shell's premium 93-octane gasoline has FIVE TIMES the cleaning agents minimally required by the EPA. This helps to keep an engine in a higher state of tune from excessive carbon deposits found on spark plugs, piston crowns and intake valves. Extra quality costs extra money - it always will.
Synthetic oil, of the same viscosity like 10W-40, does NOT have the same flow-rate qualities as regular motor oils. If that were true, what would be the big reason to buy significantly more expensive synthetic oil? Too run cooler, oil needs to flow at a faster rate through an engine at minimum. For most motorcyclists, with riding habits of an hour or two at a time, the synthetic oil fad is indeed a big waste of money. That's just enough time to run at normal operating temperature. Synthetic oil reportedly have some advantages for those making long runs in the saddle of a few hours or more or if doing the ton+ regularly. Similar protection by simply changing regular motor oil and filters every 3-4,000 miles on a motorcycle. The cost-benefit ratio is just not there for normal street riding purposes with synthetic oil, unless primarily air-cooled. Fear not though, synthetic oils too will be considered yesterday's news too once electric bikes become the new craze.
Last edited by BTRart750; 09-23-2015 at 12:02 PM.