C. Comments about Conventional
Oil
Understand, also, that any modern
oil that meets the SL or SM API performance requirements have quite a bit of
synthetic content in them. Any multivis
oil that meets SM performance specs must have a
synthetic polymer Viscosity Improver package or it wouldn't pass. So, any modern oil is a
synthetic "blend" as some companies like to market and charge extra for....LOL.
The current engine oils for gasoline engines (rated GF3 or GF4 in the starburst symbol) contain synthetic friction modifiers that improve fuel economy. That is in all oils sold as "gasoline engine" oils and are the things that you want to avoid in your wet-clutch bike. Some of the "fuel economy" attributes of the oils get mixed up in the addition of the friction modifiers.
Since the performance classifications have advanced to the current level of SM that (SG) is a long ways behind the performance capability of current oils. All of the recent development in oils has been around less deposits, viscosity improvers that do not break down and cause ring belt deposits, and high temperature (above 300) performance I suspect the only reason that they do not utilize the most current SM performance rating is to avoid any confusion with oils rated SL or SM that would ALSO be an SG3 or SG4 oil that would have the friction modifiers.
The auto companies wanted to use oils with friction modifiers for fuel economy testing improvement (on the EPA test) but the EPA would not allow it as they maintained that the customer in the field would not use that oil. So, the auto companies worked with API and the oil companies to devise the parrallel standard called SG-3 and the new starburst symbol that says "gasoline engines". The parrallel standard would utilize the API performance rating (such as SJ or SL or SM) AND it would require fuel economy enhancing additives. By creating this new rating and getting the oil companies to utilize it it insured that the "fuel efficient" oils would be available on the shelf.
In the meantime, oils that still met the improving performance requirements, such as SL, but did not have the fuel economy friction modifiers were relegated to "diesel oil" status. The performance standards such as SL are still the same so any oil rated like that is guaranteed to be pretty high quality. I think Yamaha is just hedging their bets against people using the fuel economy oils by specing the lower, SG, standard since non of the fuel ecnomy oils were around when SG was in vogue.
I hate to start a flamer with a direct contradiction but 240 F is NOT hot oil. 240 is a nice temperature for oil...conventional or otherwise. Conventional oils from the mid 90's on are perfectly capable of living for long periods of time (hundreds of hours) at 240 F. Oils of the earlier era of the 70's might not like 240 ????? but current SL and SM rated oils are perfectly fine at temperatures up to 270/280 F continuous operation.... We "allow" conventional SL and SM rated oils to run at continuous 305 for hours on end on dyno and engine cooling tests with absolutely no problem whatsoever. Be carefull of looking at oxidation rates and such published by the competition and by synthetic oil marketers. They tend to take the first uptick in oxidation rates as a "critical" point and predict doom and gloom and oxidized oil at 240 and such. Just not the case. I have run a dyno car engine making WELL over 300 HP at continous full load/full throttle/6200 RPM with conventional oil at 300 degrees for 100 hours and the oil performed fine and the engine was fine at teardown. Conventional oil just does not fall apart like the synthetic marketers tend to predict. I would consider it pefectly normal for conventional oil to run at 270 or 280 for extended periods of time. Based on the oil life monitor algorithm work done at those temps and the extensive oil sampling taken at those temps the oil is just starting to kick up in oxidation rates at those temps and above 280 the oxidation factors start to increase to decrement the oil life algorithm more dramatically.
As a case in point....my old 78 XS1100....ran it's whole life on conventional oil.....engine partially blocked by extended sport fairing and air cooled to boot. Started with the "sure death" 10W40 SE and SF oils of the late 70's and early 80's. That engine could push the oil temp above 300 on occasion running hard in hot hot weather. I would stop and stick a cooking thermometer into the oil plug hole to check it. It DID stick the rings at about 75,000 miles due to the deposit formation problem mentioned earlier with the old 10W40 oils. Tore the jugs off, cleaned the ring grooves out and reassembled. Nothing else done. Same timing chain, etc. It is still running fine at 108,000 miles. Still is quiet, no lower end noise. Pulls easily to redline. Trans works great and clutch does not slip at all. Starting to get a little piston slap when cold but not something to complain about. The conventional oils back in the SE and SF days were nothing like the current oils...and that engine lived fine on those oils with no synthetic ever near it. I have torn apart every oil filter that came off that engine and they are always clean with minimal particles and such. What particles do show up are ferrous bits from the trans it appears. That bike has been ridden reasonably hard, lots of fast cruising in Canada and out west. Lots of hot weather. Two trips up the Alcan and several times in Death Valley so it has seen some extreme conditions. If conventional oil were that bad it would have died a long time ago.
In your case, with a Ecotec in a passenger car, highly unlikely. Assuming you are talking passenger car use, not taking it to the track for lapping sessions, etc.... synthetic is pointless. Use a good quality, conventional oil, follow the oil life monitor change recommendations and stop obcessing about engine oil and it's ability to wring miraculous mileage out of an engine. If you believe all the claims of the synthetic fanatics and all the bad things that they say about conventional oil it is hard to explain how I managed to run my XS1100 to 108,000 in perfect health with SF rated conventional motor oil...Heavens!! Sacrilege. No way. That Ecotec is very robust and does not need synthetic oil nor will it benefit from it. I have seen Ecotecs run for hundreds and hundreds of hours on the dyno at full throttle, max RPM, flat out and they look perfectly fine at teardown analysis....and they all run on conventional oil. The new supercharge Ecotec for the Redline and Cobalt SS is spec'd for synthetic due to the extra temperature capability as that car is "rated" for track work but that is the main reason. The Ecotec has roller cam followers, a Gerotor style, high flow oil pump, roller timing chains, etc....so it is highly tolerant of low anti-wear ad rates and/or depleted oil so there is plenty of cushion in the oil life monitor to allow you to follow it without any reservation.
Todays oils are so good that using any off the shelf, SL/SM performance rated GF3/GF4 motor oil for gasoline engines is fine for that engine and they will easily work with the oil life monitor with plenty of cushion AND give you the fuel economy advantage. That is what I would recommend and do myself if I were you. The single biggest thing you can do to oil, for engine longevity, is to always run the engine until it is warm. Short trips are much more taxing then long commutes. If you do have to drive short trips, get the car on the highway once a week and air it out to get it good and warm and get the crankcase cleaned out...hot oil and PCV work wonders.