It's interesting to note that lower grade gas is actually more volatile then the higher grade gas. That's the problem and why it causes pre-ignition aka knock. Newer cars do contain knock sensors that detect detonation and automatically retard the spark to compensate. The delay means maximum gas expansion occurs when the piston is farther along in its downstroke and thus there's more room in the cylinder head. This reduces peak cylinder pressure, eliminating knock but also giving you less power and poorer mileage.

Actually re-reading the manual I notice a fairly significant difference. For the G35's engine it's a "recommendation" to use 91. For the G37's Engine it's a "Use" 91, quiet different from a recommendation. It even goes so far as to state temporary use of sub 91 is ok but only mixed.

 

This is true.

 

Filling up with reg over super- you save a maxium of a whopping $4.00!
Save yourselves some trouble and just use the super. If you can't afford $4.00 per fil up then I would suggest something that runs on lower octane. Additionally any money that you may save will probably be offset by worst fuel economy. This engine has high compression and if you detonate fuel before you can burn it then you are using more fuel than you normally would unless you drive like a granny. Higher octane will burn more efficiently and cleaner in these cars.

I know folks who use lower octane to save money and then go out and buy an $8.00 bottle of "octane booster" to compensate. That makes no sense to me.

 

vinny...I feel ur pain when it comes to nyc gas prices but u can't be cheap about it...bc if ur can suffers damage due to low fuel, ur warranty doesn't cover it bc u chose to put 87 in it..and trust me, u don't wanna pay for a new VQ37HR...jus do ur self the favor of getting ur gas near the Palisades mall if u care about price that much, it's cheaper in upstate ny and NJ...

 

its not that i cant afford it guys, i was just a question if you mix gases would it hurt your engine?

I will be putting super in my car.