engine RPM @ 70mph
01-30-2007, 06:31 PM
#21
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Originally Posted by toastedoats
Originally Posted by Maymybonneliveforever
Originally Posted by agrazela
Switch to a good synthetic engine oil (if you haven't already) and watch your cruising RPM'* drop another 100 or 200, reducing wear and saving fuel 
.
.Can someone correct me on that?
02-01-2007, 06:04 PM
#22
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I am not crazy. I don't know how it works, why it works, or why it even could work, but I have had five separate vehicles now that, upon switching over from dino oil to Mobil 1 (at same oil weight, and still using same brand of filters) have experienced a 100-200 rpm reduction at identical highway speed, at any but WOT (i.e., when pushing slight throttle, on C/C, or coasting):
1993 Chevy Cavalier (5W30)
1993 Dodge Dakota (10W40)
1997 Nissan Altima (5W30)
1998 Buick LeSabre (10W30)
2004 Buick LeSabre (5W30)
This 100-200 rpm reduction remained constant through all additional synthetic oil changes. In two cases (the Dodge and the Nissan), I went BACK to dino oil (lean times), and the 100-200 rpm'* CAME BACK. In the Dodge truck, I switched BACK AGAIN to synth, and the 200 rpm'* WENT AWAY again.
It'* this reduction in rpm'* to which I've always attributed the extra 5-10% gas mileage when using synthetic oil.
1993 Chevy Cavalier (5W30)
1993 Dodge Dakota (10W40)
1997 Nissan Altima (5W30)
1998 Buick LeSabre (10W30)
2004 Buick LeSabre (5W30)
This 100-200 rpm reduction remained constant through all additional synthetic oil changes. In two cases (the Dodge and the Nissan), I went BACK to dino oil (lean times), and the 100-200 rpm'* CAME BACK. In the Dodge truck, I switched BACK AGAIN to synth, and the 200 rpm'* WENT AWAY again.
It'* this reduction in rpm'* to which I've always attributed the extra 5-10% gas mileage when using synthetic oil.
02-01-2007, 07:34 PM
#23
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Don't sweat it agrazela, nobody swears to agreement when they sign on here. You're entitled to believe what you want about your own vehicles 
02-01-2007, 08:15 PM
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Originally Posted by Woody_02SilverSE
Don't sweat it agrazela, nobody swears to agreement when they sign on here. You're entitled to believe what you want about your own vehicles
02-11-2007, 07:09 PM
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Man, I just gotta weigh in on this one. Using synthetic oils may do many wonderful and almost magical things, EXCEPT lowering RPMs at any given speed (with all other factors being the same, such as using Drive vs. Overdrive). The engine has no choice but to operate the speed it has to, based on the gear selected, final drive ratio, and tire size. If you don't change those factors, the engine WILL be spinning the same speed at any given road speed, no matter what oil is in the engine, transmission, or anywhere else. There may be less internal friction (or maybe not, depending on the exact oil you choose), but it absolutely, positively WILL NOT have any affect whatsoever on engine speed.
Think of it this way, on a 10-speed (or however many speed) bicycle. Put the bike in say 5th gear, and pedal at 15 miles an hour. Stop the bike, and lube the chain with synthetic oil. Still in 5th gear, pedal at 15 miles an hour. The crank will have the exact same number of revolutions at that speed, regardless of friction. The size of the crank gear, the wheel gear, and tire size will dictate how many times the pedal has to go around to maintain any given road speed. The only way to change it is to put it in a different gear, or change the tire size. Period.
Did I just overdo that a little?
Think of it this way, on a 10-speed (or however many speed) bicycle. Put the bike in say 5th gear, and pedal at 15 miles an hour. Stop the bike, and lube the chain with synthetic oil. Still in 5th gear, pedal at 15 miles an hour. The crank will have the exact same number of revolutions at that speed, regardless of friction. The size of the crank gear, the wheel gear, and tire size will dictate how many times the pedal has to go around to maintain any given road speed. The only way to change it is to put it in a different gear, or change the tire size. Period.
Did I just overdo that a little?
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