At work today (car dealership), I actually had a customer who was a truck mechanic tell me that I should run 87-octane regular unleaded and add a gallon or two of diesel fuel since it was an octane booster!!! Said it would burn just fine and save me some money. Said his brother did it all the time in his Maxima.

I looked at him to see if he was joking, knowing I drove a G35 instead of a truck...and he didn't bat an eye.

I couldn't believe it...

 

my guess is that it would work provided you put in the correct ratio....
but be careful what goes in the tank as far as additives. Nissan doesn't like additives and warns against them, period.

From my own experience, I've had issues with premature replacement of O2 senors due to what you'd think are normal additives such as gas line antifreeze and fuel injector cleaner.

This made me cautious about any kind of additive now.

C.

 

Diesal is a very high octane fuel but it's not like it's high octane racing fuel or an octane booster. I don't think it is going to hurt the motor if it's only a gallon or so in a full tank since it will be pretty dilluted. It might help clean the motor but that's probably it. It's funny to me what lengths some people will go to save a few bucks on gas when they blow money on everything else.

 

You are saving about 20 cents per gallon if you go 87. That is about $4 if you fill all 20 gallons....not really material IMO. $4 is like skipping an appetizer at lunch....go feed your G instead

 

I concur. I'm going out to re-juice my car with some much needed octane right now.

 

From the '04 manual.

Sedan models
Use unleaded regular gasoline with an octane rating of at least 87 AKI (Anti-Knock Index) number (Research octane number 91).
For improved vehicle performance, INFINITI recommends the use of unleaded premium
gasoline with an octane rating of at least 91 AKI number (Research octane number 96).

 

I can't believe this question even popped up, the G is a luxury sports car, you shelled out the money to get a top end car yet you want to go cheap on the type of fuel? man it's premium only for me

 

Let's set some things straight.

Running 87 in the G35 won't hurt the engine. The knock sensor is very sensitive and once it's hear's knock (ie detonation), it dials back timing and sometimes richens the air fuel ratio to cool the combustion chamber. In return you may loose some HP, engine responsiveness, and possibly MPGs.

Running 87 then 91 won't throw the ECU into a fit. There are mutliple lines of code burned into the ECU. As the car is driven, the ECU is constantly using this table of code to adjust timing, A/F, etc.

87 octane isn't any more "dirty" than 91+. They all use the same detergents.

Octane is the rating of the fuel's burn characteristic. It's an anti-knock rating. Higher octane fuels are less resistant to burn. Many high compression motors require high octane to produce strong HP numbers. If you were to run low octane in a high compression motor, detontation may occur because the 87 will ignite quicker than what the ECU is ready for. Late model ECUs can compensate for this, as stated above. Too bad Nissan hasn't hired some of the guys from the Toyota/Honda powertrain divisions because those guys have developed some seriously hightech ways of safely running 87 octane is very high compression motors that range from 11.5-12.5:1. It's all in the combustion chamber design and cam timing. Nissan is stuck at 10.5:1 ratio in their VQs, which require 91 to perform optimally.

It is quite possible for a VQ to be putting out maximum HP with 87 octane assuming the car is at a higher altitude. At high altitude, the air is less dense with oxygen therefore the motor will be generating lower compression. Factory spec compression is rated at sea level air. The downside to driving at high altitude is reduced engine performance. An NA motor looses about 2-3% of it's power for every 1000' in elevation regardless of octane.

It is also possible to run lower octane fuels in cooler climates because the engine will typically run cooler which reduces combustion chamber temps. Lower combustion chamber temps reduce pre-ignition (detonation) therefore running lower octane without reduced power is potentially possible.

 

Thanks, DaveB. Informative and interesting.