With an aftermarket tune, you need premium gas. On a stock tune or ecu, you can use any grade of gas but does the car see any type of performance boost by using premium on the stock tune? Ive used both regular and premium and didnt feel any difference on my stock ecu, but that doesnt mean there isnt a boost in hp with premium. Just wanted the facts from the pros here.

 

Premium will see a slight boost in performance, but unless you can see/feel it, it probably isn't worth your extra few dimes per gallons.



If you have a 3.8, just go cheap. They're slow.

 

OEM ECU are more sensitive to fuel changes, Most OEM are wayyyy more self-controlling of a engine. It can read knock sensors ect. Most Aftermarket ECUs people don't even use knock sensors ect.



I have... 1/2/3/4 injectors/Crank/Idle valve/Coil/TPS/Air & water temps (No Cam or Knock sensors and pulled 147Bhp and loom is unclipable in 40 Seconds for engine work.





iv tryed 95-98-102-105-110 octane in the past as that's all that's sold in england. Cheapest being £1.35 a liter to £2.30 a liter. There small improvements but nothing to scream about.



A friends VW golf gained 14Bhp Running 102 instead of 95 octane. All depends on the Cars ability to adjust.

 

The ECU compensates and adjusts for fuel changes. You'll see an initial peak but over time the ECU will bring it back down. I guess you could keep resetting the ECU