On SHELL 89 grade fuel - Improved mileage? Topic is solved

[C30Vehicle]

Have 2009 Volvo C30 owners noticed a notable increase in mileage after fueling with SHELL 89 grade (SHELL Plus) gasoline?

The SHELL brand of gasoline contains Nitrogen (Nitrogen is claimed to help clean parts of the fuel-intake e.g., intake valves). Can Nitrogen-enriched fuels 89 & 91 grades also provide notable improvements in mileage in some vehicles?

[jtopiso]

Which engine? On mine (2.0i), yes: premium fuel improves mileage, but not that much as to worth the price difference.

[jimmy57]

Engines with knock sensors detect the pre-ignition or detonation that occurs with lower octane fuels. When the knock is detected the ignition timing is retarded which reduces torque. If the knock is bad enough the ECM will richen mixture. Retarding timing and enrichening the mixture decrease MPG. The posted octane number and the actual effective octane does vary. Sometimes the actual octane is as much as 2 points higher and others can be 2 points lower. I don't think with tighter budgets for government agencies that we are getting much oversight of fuel quality. In your area Shell must be one of the ones that is providing fuel that is at or above the pump posted number for the fuel grade. I had Runzheimer fuel survey access for a time in my job a few years back (not sure Runzheimer does that any more) and it was shocking for the area that my survey included that true octane and impurity levels were all over the place. The numbers were not consistently higher for name brand vs. off brand fuels. I do not know what Ffuel companies in what locales are best now but I'd say you have found Shell to be good in your area now. It can, and most likely will, change in time. I had a ford pickup 30+ years ago and it was very fuel sensitive or it knocked where it was audible. It sounded like 3-4 marbles rattling in a metal coffee can. I found that in my area price has nothing to do with octane. Big name fuel stations would rattle unless I got premium and 7-11 convenience store fuel consistently was no knocking on regular.
The detergents can have impact as the deposits in combustion chamber increase octane requirement to avoid knock.

[C30Vehicle]

My vehicle is a C30 2.5 liter Turbo.

From original question, can Nitrogen-enriched fuels esp. 89 & 91 grades boost mileage?

[jtopiso]

As explained above: better octanage allows for better combustion (although I'd have said that when know is detected, ignition needs to be *advanced* and not retarded. I've been wrong before though, so now I'm not that sure).

As knock limits how far from ideal will be the combustion, it's very likely that there will be an improvement in performance and efficiency.

Better performance can be seen as two contradictory things, depending on how hevay is your right foot: easy driving will allow for more power with the same amount of fuel, so better consumtion.
But also, more fuel can be burnt per cycle, so you get more power because you can burn more fuel per second: so you you worsen your range, but you get there faster.

[C30Vehicle]

Just fueled my Volvo C30 - no change in mileage after trying the SHELL 89-grade Nitrogen enriched fuel.

[June]

Just fueled my Volvo C30 - no change in mileage after trying the SHELL 89-grade Nitrogen enriched fuel.

For my S80 it requires 93 octane. 87 and 89 it looses 2 to 4 mpg and noticable power loss. June

[okidiver]

I've noticed no significant gains in MPG for higher octane fuels, but run Shell 93 in both my C30 and V60 because it has more detergents and I feel will keep the EGR gremlin at bay. Mo power on those rare occasions when I need it, also, YMMV....

[jimmy57]

When you advance timing the peak pressure will occur at or closer to the point where piston is at TDC with the least combustion chamber volume. If you burn the fuel in the smaller space you get faster flame travel, higher pressure and higher temp. The conditions in that case are more favorable for preignition or detonation. When timing is retarded the piston will have past TDC and the combustion volume is greater and the likelihood of the ill effects is reduced.

[okidiver]

So, jimmy57, R U saying when the computer retards the timing when it senses higher octane fuel--that be much more better--than advancing timing when the computer senses lower octane fuel?