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91 octane premium fuel?

W

Wadded Beef

Banned
It's a 2005 nissan sentra se-r spec v. they (nissan) recommend premium fuel but it's not required, unlike like some cars (350z). Is it pointless to buy premium grade over regular? I put premium in the last two fill ups and noticed a 2mpg increase, even though i've been driving it harder since the break in period is almost over. my understanding is that it retards the timing for regular grade fuel so no knocking occurs, but is there an actual difference in performance and mpg, or am i imagining things?
 
You will lose some measure of power and efficiency if you run on a lower octane, as the car's knock sensors encourage the ignition to retard timing. It varies to how significant this is on different cars.
 
Your mileage *may* have improved just due to finishing your breakin period.

If it isn't required, it isn't required; but your car will have to retard timing slightly to avoid engine knock, so you will lose some power. I don't know if it will be noticable though.
 
My car says premium fuel only but in the manual it says you can use a lower grade if premium is not available. Most of the people that own Legends use regular and have been using it for years without any problems. They do say they don't get as good mileage as when they did using premium
 
- Do what the owners manual says. If it says you can use either, then either decide with your pocketbook and get regular or with your right foot and get premium.
- Yes, you will lose some performance using regular (probably not much), as the ECU will retard timing to prevent knock.
- Your mileage improvement was probably due to finishing the break-in period. Once you are well past the break-in period (2k-3k miles), you should reset the ECU in order to get even better mileage and smoother performance (note: not better, smoother).
 
Originally posted by: iamwiz82
You buy a $15,000 car and then are too cheap to spend the extra 15 cents a gallon?
Click to expand...

It's like the thread about the guy with the $20,000 car and no health insurance for his daughter.
 
Originally posted by: Wadded Beef
how do you reset the ecu?
Click to expand...
Unplug the negative battery terminal and leave it unplugged for more than 30 minutes. This is safe to do on most cars, so I assume it's alright on a Nissan. You might want to ask Skoorb (Almighty Nissan God).
 
Hmm... What do they mean recommended but not required? That's kinda strange wording.

If they mean that the knock sensors will retard the timing and absolutely no engine damage will result, then you should use premium.
 
Originally posted by: Eli
Hmm... What do they mean recommended but not required? That's kinda strange wording.

If they mean that the knock sensors will retard the timing and absolutely no engine damage will result, then you should use premium.
Click to expand...

That's what they mean.
 
Originally posted by: aplefka
Originally posted by: iamwiz82
You buy a $15,000 car and then are too cheap to spend the extra 15 cents a gallon?
Click to expand...

It's like the thread about the guy with the $20,000 car and no health insurance for his daughter.
Click to expand...
Well, that's stupid, but I don't see anything wrong with wanting to maximize a dollar.
Unplug the negative battery terminal and leave it unplugged for more than 30 minutes. This is safe to do on most cars, so I assume it's alright on a Nissan. You might want to ask Skoorb (Almighty Nissan God).
Click to expand...
Well I've done it on my 00 maxima without problem, so it should be fine on an 05 sentra I suppose 😉
 
Originally posted by: Vic
Originally posted by: Wadded Beef
how do you reset the ecu?
Click to expand...
Unplug the negative battery terminal and leave it unplugged for more than 30 minutes. This is safe to do on most cars, so I assume it's alright on a Nissan. You might want to ask Skoorb (Almighty Nissan God).
Click to expand...

I know for WRXs you can just unplug the negative terminal and step on the brakes for a few seconds and that'll discharge whatever's left in the electrical system, don't know if it's universal
 
Originally posted by: Vic
Originally posted by: Wadded Beef
how do you reset the ecu?
Click to expand...
Unplug the negative battery terminal and leave it unplugged for more than 30 minutes. This is safe to do on most cars, so I assume it's alright on a Nissan. You might want to ask Skoorb (Almighty Nissan God).
Click to expand...

ahh, kind of like taking out the cmos battery on a mobo?
 
Originally posted by: Wadded Beef
Originally posted by: Vic
Originally posted by: Wadded Beef
how do you reset the ecu?
Click to expand...
Unplug the negative battery terminal and leave it unplugged for more than 30 minutes. This is safe to do on most cars, so I assume it's alright on a Nissan. You might want to ask Skoorb (Almighty Nissan God).
Click to expand...

ahh, kind of like taking out the cmos battery on a mobo?
Click to expand...
Yep.

 
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