regular unleaded with 2003 supercharged??

My girlfriend just bought a 2003 supercharged xterra.
I like it, and that says a lot because I'm an owner of 3 older land cruisers. This nissan looks very durable.
Anyway, do we really have to run the expensive fuel or can we get away with regular?
I don't want to damage any expensive powertrain components, just lessen the fuel costs.
My old cruisers will run on ditch water fuel so this requiring 91 has kinda got me going.
Thanks.

If you love the engine, keep it happy, use 93 octane.

If you have to use cheaper gas (i.e. nobody sells 93 in your area), use an octane booster, but it'll end up costing he same $$.

$.30 more per gallon is a lot cheaper than a new $6000 engine not covered under warranty because you failed to follow the instructions...

not trying to flame, just trying to save you future pain and $$$.

I have a 02' SE/SC and I used to run the good stuff only. I decided to try a couple of tanks of 87 octane after gas prices went way up and haven't noticed any spark knock. When I pull my trailer or go playing, I always gas up with 93. My X is a 5-speed, I don't know if that makes any difference.

Read your manual, see what it says about using <91 octane, in a pinch.
The knock sensor would allow it by retarding timing, but the knock it will continually detect can be harmful. Not to mention power will probably be cut back to less than the non-supercharged version.

Don't be a cheapskate, it's not worth it for <$4 a tank.

Brent

I know this sounds silly coming from a guy who owns FJ40's, and they only get 12mpg.
But premium gas where I live (Saskatchewan)is running about 96 cents/litre.
That works out to $4.35 a gallon.
I do not want to hurt the motor since it only has about 60 miles on it so far,so I guess I may be stuck with the higher priced gas.
But I am looking forward to taking this truck out to play with my FJ40 which has an SM420, low t-case gears, 5 inch lift, 35's ,lockers and a XD900i up front.

I am assuming the water injection helps keep charge temps down to prevent detonation.
I don't think it would be worth the trouble. But if I'm not towing the trailer or running hard I thought that regular might be ok for going back and forth to work. But concensus says maybe not.

Don't you have mid grade? If you have a mid grade gas option you should be fine for commuting if you're not loading down the truck or climbing steep hills. I wouldn't stoop to regular though; too much of a workout for the knock sensor.

There are just two grades of fuel here.
87 and premium. I guess if there was mid-grade gas I would use it if it met the minimum requirements.
I really wish the truck would take regular though, oh well.

IF you spent the extra money to have the extra ponies, why would you even consider not feeding it correctly? If you don't want to pay the prices you should have gotten the normaly aspirated engine.

I just bought my X a couple weeks ago and the salesman told me that as long as I feed it the good stuff every couple of tanks then I could get away with regular octane...

For what it's worth, I toyed with the idea and it seemed silly to risk it for such a small price. I know it adds up but so does maintenance, that's all it is. You could go a couple extra hundred, or thousand, miles on your oil too, but it all comes down to how well you take care of your X.

I'd like to be able to tell the next buyer of my X that I ALWAYS gave it premium gas. Not, only when I thought it needed it. It's the same reason I replaced the transmission in my camping van before I was going to sell it. I like to sell my stuff with a good conscience.

by the way... Van is still for sale!

I noticed on the inside of my gas cap it says "Premium fuel is RECOMMENDED". I thought that was odd considering what the manual said.

If it's true that the SC only actually works under WOT, then I would think normal gas is OK if you didn't floor it. True? No?

Jeezus F'in Christ people! Has it not been made clear yet? Don't be whiny cheapskates, and don't second-guess the WELL-TRAINED engineers that designed the damn engine! Put the good stuff in and move on!

I heard that! It's amazing how poor people suddenly get.

But that is money that could go for beer. Sweet sweet beer.

SC does not only work under WOT - review the design of the system and you'll see it is based on a vacuum motor and will provide variable boost in different circumstances... If you have the means to watch the bypass solenoid power you'll notice that just after idle it is enabled, and stays on throughout vehicle operation, including WOT. The bypass operation is controlled by the calibrated leakage rate motor. A vacuum/bost gauge will also show varying boost occasionally.

Yes, I agree that the conditions that cause detonation are worst at WOT, but stop and go driving with AC on full in texas heat can also cause detonation... so, while you can get away with regular (the manual states as much) it's not reccommended, because neither you, nor the engineers, know what driving conditions you will encounter. Running super octane means that your will not risk your engine's integrity no matter what you run into down the road (yes, again, with exceptions).

For me, that means that since I drive like an asshole, I'm more likely to encounter detonation and I would be safer running super. If you drive like grandma, you can probably cheap out, but youve been warned.

-=RB

I know that allot of you don't really understand forced induction very well, but let me see if I can put it simply. :rolleyes:

Normally the engine computer is tuned to use premium gas on a forced induction engine (Turbo, SC). This allows them to run more timing and less fuel for better power.

Most factory tuned cars are designed to limp on regular fuel even if it wants premium. This prevents bent rods and such when “Jo consumer“ decides to forget that it wants the good stuff and puts 87 in.

This is normally accomplished by a knock sensor. This is basically a little microphone that is attached to your block and listens for certain frequency noise above a certain decibel level.

When it hears knock, it retards the engine timing. Retarded timing = Less power. This can be a big loss, as allot of the time the knock sensor will pull allot of timing just to be safe.

Bottom line, low octane gas=really crappy SC performance. Also the knock sensor is hearing detonation, maybe very mild, but it is still there. If you are getting detonation, you are hurting you engine.

Use the 91+ octane and stop risking a bent rod for cents a gallon.


Sean