[Arizona Pro-Photo]

As I have posted in other threads I have been trying squeeze every MPG I can out of my X due to high fuel costs.

I posted a thread about the driving techniques called Hyper-Miling, which did improve MPG up to an average of 19.66 MPG for city and just over 22 highway. The EPA rating is 14 city and 19 highway, so hyper-miling did make a significant difference.

I posted a thread about using high flow air filters, such as K&N. The higher airflow did improve mileage to 20.84 MPG city, but highway pretty much stayed the same. Plus, as some of you pointed out the higher airflow filters will allow finer dust particles into the engine, so driving on really dusty roads will require cleaning that type of filter very often and changing the oil more frequently. Fortunately 90% of my driving is on pavement so my X is not exposed to high dust conditions.

I have now decided to try octane boosters to see if that would make any difference.

According to the data about my naturally aspirated 2004 V6 Xterra the compression ratio is 8.9 to 1 and if you have the 4 cylinder version it is 9.2 to 1.
And it said in the service manual that it runs best on mid grade or premium, supercharged or not.

Unfortunately gas stations where I live don't sell mid-grade and premium is just too expensive.
Therefore I decided to see if an octane booster would make any difference.
After two tests I did see an MPG improvement.
My city mileage is now at 21.47 MPG, so the octane booster did have an effect.
The octane booster I used is called Turbo 108.
I got it at O'Reilly's, but it is probably sold at other stores as well.
The price ranges from $5.79 to $6.49 a bottle, plus your local sales tax.
That is about the cost of 1.50 gallons of regular gas, yet it will treat up to 16 gallons of gas.
It supposedly boosts the octane to 108 for 16 gallons of regular 87 octane. I figure that since my tank holds 19.4 gallons the extra 3.4 gallons would dilute the octane booster just enough to make it equivalent to premium which is 93 octane.

I did notice that the engine is idling very smooth and acceleration seems better. And since the MPG did increase a little the octane booster did have an effect.

I included a photo of what the bottle looks like so if any of you want to give it a try you'll know what the brand looks like.
Now don't confuse octane booster with fuel injector cleaner.
Fuel injector cleaner is meant for cleaning fuel injectors and removing small amounts of water that might be in the gas. Fuel injector cleaner will NOT increase octane, so make sure to carefully read what's on the bottle if they don't sell this brand where you live.

Now I know that some of you will disagree with using any octane boosters, which is why I am sharing the MPG I have managed to obtain with it. After two tests the figures don't lie. It did make a difference for me.
However, since some Xterra's have different engines, and some are supercharged, I don't know what results you will get.
As with most aftermarket products results will vary.
All I can say that it might be worth a try to see if it might benefit you.

 

[notarustedgarbagecan]

I thought the vg33e was 8.9:1?

 

[Arizona Pro-Photo]

I thought the vg33e was 8.9:1?

I rechecked the service manual and it is 8.9 to one.
It's the 4 cylinder that's 9.2:1
My mistake on that.
The service manual covers all the different engines that were available for mine and I misread the section on engine specifications.

But there is not much of a difference between 8.9 and 9.2 in terms of actual compression. I did a calculation on the difference and there is only a 5 PSI difference between 8.9 and 9.2 which is not a big difference in terms of performance.
I surmise that the 4 cylinder needs the slightly higher compression because it is a smaller engine.

On a side note, the supercharged version has 8.3 to one, which is significantly lower in compression compared to the naturally aspirated versions. However, the lower compression is necessary for the supercharged version because more air is being crammed into the cylinders.

In any case, the manual does say that mid-grade or premium is recommended for all of the engines, supercharged or not.
The octane booster I used, however, did have a measurable improvement on MPG and I noticed it starts quicker and has a smoother idle.
The idle is so smooth that there is very little vibration. So the octane booster was beneficial, at least for mine.

However, I will correct my original posting for the compression.

 

[Blackberry]

My Frankenstein supercharged engine has 8.9 and I just bought a bottle of octane booster to try it out. I keep getting the supercharger in bypass mode without any codes. This usually caused by detonation, so I’ve filled it with 91 and set the base timing back to 7 or 8 degrees. It keeps setting so next step is 5 degrees with octane booster and if it keeps kicking then I’ll probably do a knock sensor bypass

 

[Arizona Pro-Photo]

My Frankenstein supercharged engine has 8.9 and I just bought a bottle of octane booster to try it out. I keep getting the supercharger in bypass mode without any codes. This usually caused by detonation, so I’ve filled it with 91 and set the base timing back to 7 or 8 degrees. It keeps setting so next step is 5 degrees with octane booster and if it keeps kicking then I’ll probably do a knock sensor bypass

It could be because the compression is just too high for a supercharger. I looked up the specs and the supercharged versions have 8.3:1 compression, so if you added the supercharger to a naturally aspirated engine you might have to find a way to dial down the supercharger's boost so that it is better balanced with the higher compression.
Just wondering, but when you added the supercharger did you change or have the ECM reprogrammed? I do know that the ECMs are calibrated for whatever compression and ignition timing the original engine had. By adding a supercharger that original ECM programming might have gotten upset.

That's why I mentioned in my original posting that I have no idea how the octane booster would perform on supercharged engines.