I finally got my father's 2k Max, but he has been putting regular in it for the life of the car. I read that it is supposed to use premium.
Should I start using Premium after I put in a fuel injector cleaner? I know those cleaners aren't recommended, but is there anything I could do to undo the damage to the car for those 2 years when its had regular unleaded gas?
There is no knock or pinging...I just want to take care of the car so that is why I am thinking about making the switch to Premium.

Thanks
GEORGE

 

If there is no knock or pinging then there is no engine damage from using 87 octane. Just switch over the 93 octane and enjoy less money in your pocket.

 

doesn't the manul say to use 91

 

91 or better is required and is considered premium.

 

91 will reduce carbon deposit in your engine and prevent the engine from retarding the timing. The reason you don't hear knocks is because the knock sensor compensates for the lower octane.

 

Any 93 octane in San Diego? I remember it used to be 92, not it's 91. What's the reason for that?

 

I haven't seen any, but 91 will probably suffice. The compression ratio doesn't mandate that high of octane.

 

It was recommended that i use premium in my 95 Maxima, however i never had pinging with 87 grade so i used that for the entire time i owned it 1995 to 2002. I put on 240,000km (144,000 miles), and never had any problems at all. I have never heard of anyone having problems using 87 grade, so if there is someone out there i'd like to hear about what problems they had. I'm also using 87 grade in my 2002 Maxima.

 

It is unlikely that 87 will cause damage or carbon deposits. It will cost signifigant hp and 2-4 mpg compared to premium, however - there's no real savings - better mpg with more expensive gas = worse mpg with cheaper gas, but it will run better.

 

NEVER anything lower than 91 for my max....usually 93. I can actually feel the difference....

 

It's alwasy best to run teh proper gas.
The reason you dont have any damage is because your knowck sensors retarded the your timing, casuing loss of power and less mpg.
The less mpog is easily more than enough to offset any savings you may have had, from gassing up on the cheaper gas.

You are also using up a great amount of your built-in safety reserve, and risk real damage in case your regular ever not meets 87 spec.
In summer when you fuel boils in the rails during heat soak, you especially need as hi an octane as you can get.

Fred...

 

What does it feel like?

 

This discussion has been had several times before. There are people with experiences and reasons both ways. I use Premium 93 Only. Why? Because:
1.)The owner's manual recommends it
2.)Prevent knocking/pinging
3.)Better safe than sorry
4.)I'm not a cheapass. I can afford a few extra dollars per fillup. Unless gas prices skyrocket even more, I'm still paying less for a full tank of premium in my Max, than a full tank of Regular in my Grand Cherokee. And it lasts longer too.

But to each his own. If I was 100% sure it made no difference at all, I'd probably use the cheaper one too, but that's not how I feel about it.

 

There is not a 2-4 mpg difference. Perhaps, 1 mpg at best in city. I can, however, feel the difference in power and response. I would only use 93. I got a couple of free fill-ups of what I assume is 87. That's the only non-premium my car will ever get.

 

The sales people and managers at my Nissan dealership use 89 octane all the time. When they give you the complimentary free tank of gas it's almost a certainty that it's 87 or 89 octane.

I've run my 02 Maxima on regular with no noticeable problems. I will admit that the motor seems to be a lot more responsive with 91 octane or higher. The majority of the gas I put in the car is 91 octane because the car seems to run better on it.

 

I wonder how many of us are paying for premium and getting regular. or regular with kerosene (yes there was a report where a gas station owner was cutting the gas with kero).

I may be wrong here, but the ecu probably senses the knock before you can hear it. I'm thinking that if the timing gets retarded, and you keep using regular, so it stays retarded the damage if any will be negligable. If you switch back and forth and the ecu has to constantly compensate, that would lead to more knocks, and then more damage.

 

You're right, the ECU is constantly making changes, I've heard it makes over 30 adjustments per second. Switching back and forth between regular and premium probably wouldn't require the ECU to relearn anything. As for any long term damage, I don't know.

 

it says so in the fuel tank, plus you save a few bucks on gas, but if detonation does occur ( long term process, build-up) then the price to fix the car won't be a few bucks.
just my . 02