I think if you use top-tier fuel, the benefits are going to be marginal. I only ever used it on my GTI since it was an over-50k-miles used car at the time lol. It might help with injectors, though not sure if that will help your fuel consumption.

 

Ohh ok
I use 91 octane at all times.

 

I sure hope so! That is what's specified in the manual.

By "top-tier", I mean fuels that are Top Tier certified based on their additives. The additives in these fuels should do a great job keeping the combustion chamber clean and possibly the injectors too - hence, I don't think additonal fuel additives like Techron are really needed in all cases.

As long as you stick with name-brand gas stations you are most likely getting Top Tier.

 

Yeah it's been getting name-brand gas since day 1.
I'll check the spark plugs tomorrow morning.

Not entirely sure what else to check at this point since the problem doesn't make sense.

 

I'll have to check the Invidia axle back as well since most people said they re-used the OEM donut gasket, which is what I did, I'm wondering if I should have put the new donut gasket on.

A bad donut gasket falls under this symptom (bad gas mileage).

 

[QUOTE=arentz07;11300672]I'm not sure what the fuel system cleaner is at the dealership you go to, but when I asked my prior dealer about it, it was essentially some Techron. You can DIY this for a lot less than the dealer. I mean... a LOT less. They were charging $150 for that service when I went. A bottle of Techron at Wal-Mart is under $10.

Lexus branded should be concentrated Techron which is what I buy from Walmart as well. Gumout is an alternative for half the price and I heard it does some work as well.

Edit: Hawaii doesn't have 93 octane and the highest is 92 which shouldn't make a big difference. However Hawaii and Alaska are the two states that states to use fuel cleaner every 5k miles.

 

Interesting. I don't think octane will really make a difference in mileage, maybe a small percentage if anything... probably next to nothing with only a 1 AKI difference. I guess AK and HI count as "harsh" driving conditions?
Anyhow...

 

Looks like I found the issue... not sure what caused this to begin with.

When standing in front of the car, it's the third spark plug, the 3 others are fine:

 

Update:
Fixed the spark plug issue but the gas consumption issue is still there.

I'll change the donut gaskets this week and see if that solves anything.

 

The counter for average fuel/100KM is completely off. No clue why the counter is off though.
After calculating it manually for 3 fill ups, the car averages 7-8L/100km.

 

Found the culprit, switched back to the BMS intake with AEM air filter and the readings went back to normal (7-8/L/100 km).

Never putting back a Fram air filter on this car.