Fuel Grades
 

Ok, who uses regular gas, and who uses premium? If you use premium have you noticed an FE difference in the two?

It depends. I buy regular for the Elantra and Shell V-Power (premium) diesel for the TDI.

i choose regular for my cavalier, but when i had my focus i had the ecu flashed and could only use premium.

im going to on the next two tanks however give premium a shot and see if there is any difference, but i look at it as regular is cheaper, so it would have to be a great difference in FE to make the complete switch.

I use 89 in my DD an 87 Turbo Volvo. The owners manual says 91 but since I hardly ever go into boost why should I spend the money on octane I'm not using. 87 makes the car run poorly and it has pretty poor pick up if you have to put the pedal down.

I've used both premium and regular in my bike and have noticed no difference. The manual says use premium, but I have a small engine that just doesn't have the compression to completely burn premium.

Will -

I ran Chevron 91 last year because of my HAI (hot-air-intake => lean-burn => higher octane is better to avoid knocking/pinging). I switched to 87 when the gas prices got too high, didn't notice a change, and never switched back.

I have a hankering to up the octane again because my car is *different* from last year. I also think it has been on 87 for so long that I might be able to detect a difference in the way it drives (big *shrug*).

CarloSW2

Even if it did yield better FE, from a cost perspective it would have to make up for that 20 cents or so per gallon to truly make it economical. I wouldn't mind seeing some data on it. I'm not quite sure it's worth the gamble of higher fuel prices for few tanks, personally. I'm sure it's been looked at before somewhere.

Bailout at CleanMPG, with his commute up and over a rocky mountain pass in a Yaris, tested this.
regular was best
-4% mpg with midgrade
-9% mpg with premium

I think I'll stick with the cheap stuff.

When I had my HAI (160F) I used premium to prevent detonation, but the cost-benefit was off. Now, intake temps are 100-120F with full advanced timing and no ping with near-full load (some knocking at high RPM, so I don't go there much).

The TSX "requires premium", but runs just fine on regular. The savings add up. FE is the same too. There's a bit of stumble from time-to-time at 6k RPM with VTEC, but again, very rarely used.

Long live 87!

RH77

In my 11 years old turbo diesel I used only regular and mid-grade during years.

One of the rules to eco-drive is to shift up soon, but it had difficulties to stay at 1500rpm. During the first premium tank I felt changes and now (at 4th tank) it can accelerate from 1200-1300rpm.

Because it permits me to improve my eco-driving style premium permits me to have a better mileage. Currently I'm staying with the premium as while I'm saving 33% of diesel, I'm saving 30% of money. May be one day it will be the placebo effect... My mechanic maintains my car, but premium seams doing things my mechanic doesn't...

Denis.