Most people here will say 93. As long as you're not drag racing the car or doing any type of redlining often, 87 grade will be fine for you. If not, you'll probably knock & ping your motor to death.

I don't know about advanced timing on the SPEC, but a few people that might know will show up soon.

 

ok so I plugged some different words in the search and got what I wanted.

I was hoping that it would retard for lower octance gas rather than advance for higher octane... Does that make sense...

I guess what I mean is I am glad the CR is up to the higher octane.

 

Ah! Yes. I believe that the computer automatically retards or advances the timing a bit, depending on the gas grade.

 

If you put lower octane gas in the car there is the chance that it will predetonate in the cylinder, especially on hot days or when under heavy acceleration. If this occurs, the knock sensor will hear a pinging (and you will too if you're paying attention, like bb's falling on your hood) sound and retard the engine.

If you ping, it retards
If you don't ping, it doesn't do anything
I don't know the criteria for un-retarding the engine once its been retarded

 

If you put lower octane gas in the car there is the chance that it will predetonate in the cylinder, especially on hot days or when under heavy acceleration. If this occurs, the knock sensor will hear a pinging (and you will too if you're paying attention, like bb's falling on your hood) sound and retard the engine.

If you ping, it retards
If you don't ping, it doesn't do anything
I don't know the criteria for un-retarding the engine once its been retarded

I believe the ECU adjusts spark timing nearly continuously to avoid knocking. Thus, if the spark timing is retarded, the knock sensor will advance timing once it does not "hear" knocking anymore. On a related note, in the July 2003 issue of Sport Compact Car, there is an article about the 2002 SE-R Spec V that states the knock sensor on these vehicles is extremely sensitive, even "hearing" knock and retarding spark timing when there was no pre-mature detonation. Their fix was to unbolt the knock sensor from the engine (but not the ECU) and zip-tie it to the power steering hose. Note that at this point, the knock sensor would be unable to adjust for pinging, so using lower grade gasoline and the ensuing pinging would eventually cause damage to the cylinder walls. Going back to octane ratings, I believe the manuel recommends 91+ ocatane fuel (Premium grade in CA). This would be the ideal readily-available fuel for the Spec V.

 

Does the qr25de in the altima require 91 octane as per its owners manual? If not, why does the specv need it and not the altima as they have the same engine and HP?

 

If the owner's manual says 91 octane, then that's probably what's best. However, the qr25de in the Spec V is tuned for performance as it has more torque than Altima (180 vs. 150). The increased performance tuning on the Spec V qr25de would make a higher-grade gasoline more important, though in both cases the ECU would retard the spark timing if it senses any pinging. Using lower-grade gasoline would only increase the chances of pre-mature detonation.

 

super 94+ octane, she has never seen a drop of anything else

 

If you ping, it retards
If you don't ping, it doesn't do anything
I don't know the criteria for un-retarding the engine once its been retarded

I hear once your retarded you have to stay that way.. LOL

 

If the owner's manual says 91 octane, then that's probably what's best. However, the qr25de in the Spec V is tuned for performance as it has more torque than Altima (180 vs. 150). The increased performance tuning on the Spec V qr25de would make a higher-grade gasoline more important, though in both cases the ECU would retard the spark timing if it senses any pinging. Using lower-grade gasoline would only increase the chances of pre-mature detonation.

The Altima has the same torque rating as the Spec V (180)

 

The Altima has the same torque rating as the Spec V (180)

Yeah but the funny part is 2.5 altimas recommend gas is 87 Oct all day long....so why would the Spec V suggest anything higher? Its basically a Altima engine dropped in a sentra chassis, so whats the difference engine wise?

 

I think it has to due with the fact that Nissan expects the Spec's to be driven a lot harder then a family style altima. So if you are going to be flooring and redlining may as well decrease the chance for knock. But hey, this topic has only been discussed 198769445 times.

 

Yeah but the funny part is 2.5 altimas recommend gas is 87 Oct all day long....so why would the Spec V suggest anything higher? Its basically a Altima engine dropped in a sentra chassis, so whats the difference engine wise?

tuning

 

I used Mobil Super for a long time, then once prices started rising I put 87 in. Haven't really noticed anything. I just hope I didn't make a mistake by being cheap on gas.

 

Honestly... I wouldn't put anything lower than mid-grade during the summer times. When the air is hot, it can cause possible lean conditions.. You can definetly run it safely on 87... but it will feel a bit sluggish since the timing will drop

 

I been using 91 octane up till recently, when gas price skyrocketed well over a buck for a litre... been using 87 since. Initially I experienced lost of power, when i drive the car, the acceleration feels like i have 5 more passengers in the car. but after a couple weeks, that went away, i guess the ECU adjusted and i got the power back...

 

I used 94 octane when sunoco had it. Now I use 93 usually V-Power.

 

I dunno....SE-R and alti 2.5 Requires atleast regular, while the spec v requires premium? I have a SE-R and have used both. I don't really notice any difference except for the price.

 

We have Sunoco Ultra 93 & 94 in Cleveland...pricey as hell , but oh well .

 

The Altima has the same torque rating as the Spec V (180)

My bad! I could have sworn I saw 150 lb/ft somewhere...doh! Maybe they do just expect you to drive it harder. Or maybe it has something to do with the way the fuel map/ecu is calibrated?

 

You know I get criticized alot for opting to use 91 when it could run 87. All I say in response is.... My tank lasts a week and half based on my normal driving habits... Going on an average of $3.00/gallon as of late...it has roughly translated to 2-3 bucks more than 87 at every fill-up which would add up to roughly 7-8 bucks extra a month! Thats less than a twelve pack for something I use EVERYDAY and is crucial to me. So yea if it takes 2-3 bucks extra for something I have to buy anyways(gas) then WTF?!?!

 

yay gas price is going down!!!!!

 

pemex!!!!!! try it its cheap too!!!!!

detonation makes your exhaust sound MEAN!!!!!!

 

haha.... er... i use 91 octane here..... and only that..

CC

 

I dunno....SE-R and alti 2.5 Requires atleast regular, while the spec v requires premium?

No, it RECOMMENDS premium. Your engine will NOT explode if you use regular.